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Gewge E._ M~ Jr.
Dept. ~oology
Unive!.my Of Wyoming
~e1 Wyoming 82071 <' AJ\L1S
_N.as\(3. Resources
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ORAU-142
Impacts of
Transmission Lines·
on Birds in Flight
Proceedings of a Conference
January 31-February 2, 1978
Oak Ridge Associated Universities
Oak Ridge, Tennessee
June 1978
Sponsored by the
Fish and Wildlife Service
U. S. Department of the Interior
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ARLIS
Alaska Resources
Library & Information Services
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Oak Ridge Associated Universities is a private, not-for-profit
association of 45 colleges arid universities. Established in
1946, it was one of the first uriiversitycbasetl, scienee-related,
cofl)orate management groups. ·It . conducts programs of
research, education,· ihformation, and training for a var'iety
of. private ahd governmental organizations. 0 RAU ·is noted
for its cooperative programs and for its contributions to'the
development of science and human resources in the South.
··n1
NOTICE
This report was prepared as an account of work sponsored by
an agency of the United States Government. Neither the
United States Government nor any agency thereof, nor any
of their employees, makes any warranty, express or implied,
nor assumes any legal liability or responsibility for any third
party's use or the results of such use of any information,
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represents that its use by such third party would not infringe
privately owned rights.
Available from the National Technical Information Service,
U.S. Department of Commerce, Springfield, Virginia 22161.
Please send all price inquiries to NTIS.
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The workshop on Impacts of Transmission Lines on
Birds in Flight was sponsored by the National Power Plant
Team of the Office of Biological Services, Fish and Wildlife
Service, in cooperation with Oak Ridge Associated Universi-
ties. It was conducted under the Federal Interagency Energy/
Environment Research Development Program, Office of
Research and Development, U. S. Environmental Protection
Agency, and Interagency Agreement 40-570-76 between the
U. S. Department of the Interior and the U. S. Department
of Energy.
Project Officer:
Dr. Kenneth Hoover
National Power Plant Team
Fish and Wildlife Service
U.S. Department of the Interior
Ann Arbor, Michigan
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Preface
Progress to alleviate the national and world energy prob-
lem will come as individual issues are identified and accept-
able solutions implemented. One of the specific issues to
emerge in the last few years in the United States and one that
is delaying construction of electrical distribution grids is the
real-or potential-impact on birds in flight. Therefore, the
National Power Plant Team, Office of Biological Services,
U.S. Fish and Wildlife Service, requested ORAU to organize
and convene a workshop of knowledgeable experts to exam-
ine this issue and options for dealing with it. The participants
are listed at the end of this report.
Dr. Stanley Anderson ably served as Conference Chair~
man. He was assisted by a Steering Committee consisting of
Kenneth Hoover, Philip Johnson, Roger Kroodsma, and
Robert Welford. Prepared papers were invited and are in-
cluded here as authored contributions. Five working groups
were organized, and we express appreciation to the following
individuals for their service as chairmen or rapporteurs of
these sessions:
Bird Behavior-Sidney Gauthreaux, Jr.
Habitat-James Tanner
Mitigation-Daniel Willard and Larry Thompson
Managemen-t Options-Spencer Amend
Research Needs-'-Milton Friend
Their efforts in capturing the often spirited discussion
and recording both a'greement and lack of agreement-a dim:...
cult proposition at best-are appreciated. Alf of the authorS
are indebted to David Armbruster, ORAU, for editori'al!
assistance.
. . Funds for support of this workshop We~ provi£ied by tfte
Office of Biofogfcal Services, U.S_ Fish and Wildlife Servi:ce,
and by the Environmental Protection Agency. Clearly, tl!te
ideas and suggestions expressed fn this repoh do not repre-
sent or imply any poHcy or position on behalf of sponsoTiltg
agencieS; or participants' institutions.
PflWrp L Johnson
Executive Di:rector, 0 RAU
VII
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Table of Contents
Introduction-Kenneth Hoover .......................... 1
Keynote Address: The Impact of Transmission Lines on Birds
(and Vice Versa)-Daniel E. Willard ...................... 5
Response-Dale K. Fowler ........................... 15
Response-Spencer Amend ......................... : 19
Migratory Behavior and Flight Patterns-Sidney A. Gauthreaux, Jr. .. 23
Transmission Line Wire Strikes: Mitigation Through Engineering
Design and Habitat Modification-Larry S. Thompson ........ 51
Effects of Transmission Lines on Bird Flights: Studies of Bonne-
ville Power Administration Lines-Jack M. Lee, Jr ............ 93
Evaluation of a Proposed Transmission Line's Impacts on Water-
fowl and Eagles-Roger L. Kroodsma .................. 117
Transmission Line Engineering and Its Relationship to Migra-
tory Birds-W. Allen Miller ......................... 129
Routing Transmission Lines Through Water Bird Habitat
in California-Edward W. Colson and Ellen H. Yeoman ....... 143
The Klamath Basin Case-Ira D. Luman ................... 149
Working Group Summaries ........................... 167
Behavior ................................... 167
Habitat .................................... 172
Mitigation .................................. 174
Management Options ........................... 182
Research Needs ............................... 184
Workshop Summary-Stanley H. Anderson ................. 195
Data Base on Avian Mortality on Man-Made Structures-
Nancy S. Dailey .............................. 199
A Selected Bibliography on Bird Mortality Involving Overhead
Wires-Nancy S. Dailey and Michael L. Avery ........... 201
Participants ..................................... 207
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Introduction
Kenneth 'Hoover
U.S. Fish and Wildlife Service
The amount of land used for electric power generation
and transmission in the United States is expected to triple
during the next 30 years. Current and future patterns of
electric power transmission and distribution lines across
the country will increase the potential tor interference
with the daily, seasonal, and migrational movements of
birds.
Habitats and flight pathways of birds are unavoidably
altered by the presence of overhead powerlines and asso-
ciated structures. Migration and distribution patterns will
also be affected if birds avoid areas adjacent to these
structures. The overall impact of transmission lines on bird
movements, however, is not fully understood, although it
has been the subject of an increasing amount of research
in recent years. While there are many documented cases
of birds of prey, waterfowl, and other large birds found
dead or injured near transmission lines and towers, the
exact cause of death or injury has often been indetermin-
able. Virtually no data are available on the impacts of
transmission lines on smaller birds.
Biologists and other decisionmakers are often called
upon to determine if proposed lines will, or existing lines
Kenneth Hoover
do, cause bird collisions, or whether nearby habitats may
be affected by the presence of such lines. Frequently they
must rely on inadequate information to address these
problems or attempt to predict such impacts in a variety of
experimental ways.
Currently, proposed sites for transmission lines are
evaluated on the basis of several considerations. Among
these are
1. Proximity of these sites to certain types of habi-
tat
2. Probability of seasonal inclement weather
3. Use of these areas by birds during the migra-
tory, breeding, and wintering seasons
4. Use of these areas by individual species and the
behavioral characteristics of those species
5. Design of proposed transmission lines and
towers
6. Possible mitigation to reduce the impacts of
birds in flight
The lack of a unified body of data from prev1ous
research and the absence of a universal approach to study
the problem have hindered its resolution. The U.S. Fish
and Wildlife Service and others have frequently faced the
question of impacts of transmission lines on birds;
however, no one individual or agency has been able to an-
swer this question adequately. Furthermore, much
existing information is not specific to transmission line
impacts.
To review the current state of knowledge on this
subject and to draw together sources of information, the
National Power Plant Team (U.S. Fish and Wildlife Ser-
vice) recently sponsored a "Workshop on the Impacts of
Transmission Lines on Birds in Flight." Three major
questions were addressed during this workshop:
2
1. What is the magnitude of the problem of
birds striking transmission lines and re-
lated structures?
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2.
3.
Introduction
What are possible short-term solutions to
this problem?
What are the best approaches to use in the
future to solve this problem?
Resolution of these questions will enable those groups
concerned with transmission line impacts on birds, such
as the U.S. Fish and Wildlife Service and other federal
conservation and regulatory agencies, state fish and game
commissions, electric utility companies, and con-
servation organizations, to more accurately predict such
impacts.
Pooling of information was facilitated by the presence
of professionals from diverse technical backgrounds
representing many of the organizations mentioned above.
A group discussion on each major issue was followed by
working sessions during which participants combined
their expertise to draw specific conclusions and develop
recommendations. Although participants represented
groups with different interests and goals, much valuable
information on organizational structure, hierarchy, and
responsibility was exchanged and enhanced
communication between these organizations.
Finally, the workshop has stimulated the formulation of
research plans and coordination of research efforts result-
ing in studies utilizing similar research techniques. Thus,
the first step has been taken toward creating a data base
which will be useful in answering the three questions the
workshop addressed.
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Keynote Address
The Impact of
Transmission Lines on
Birds (and Vice Versa)
Daniel E. Willard
School of Public and Environmental Affairs
Indiana University
There is no controversy about whether birds collide
with transmission lines. Almost anyone who watches
birds in the vicinity of lines has seen a collision. Gary
Krapu ( 197 4) has reported several well-documented cases
in North Dakota, and Bill Anderson (in press) has done the
same for Illinois. The question turns on the importance or
value of the fatalities. Anderson and Roger Kroodsma
(1977) have questioned the importance of the collisions in
terms of the bird populations. Roy Hamilton asks, further,
how much is it worth to try to avoid collisions.*
Transmission lines seem to have two kinds of effects
on birds: physical and electromagnetic. I will discuss only
the physical in terms of collisions. (There is good evidence
that birds are electrocuted by towers and lines, but the
number seems small. Some authors have reported navi-
gational disorientation and physiological damage result-
ing from birds' passing through electric fields. The evi-
dence is inconclusive, but, given the increasing number of
ever higher voltage powerlines, it would appear that seri-
ous and careful study by unbiased-or several equally, but
* Roy Hamilton 1977: personal communication.
5
Daniel E. Willard
oppositely, biased-groups is called for. The importance of
electrical effects needs discussion here.
Several authors have reported on the fatality rate due
to collisions. Stout and Cornwell (1976) summarized the
causes of death reported in all the literaturetheycouldget.
They estimated that 0.1 percent of the deaths were caused
by collisions. The largest category of collision W<1S trans-
mission lines of one kind or another. Roger Kroodsma
(1977) reported that less than 1 percent of the nonhunting
waterfowl deaths in the vicinity of the Red Wing
Minnesota Power Plant were powerline related. He, like
others, points out the much higher mortality rate due to
botulism and, of course, hunting. Of the waterfowl
populations he studied at a power plant in Southern
Illinois, Anderson (in press) reported 0.4 percent mortality
due to powerlines. Over a period 9fa a decade, biologists at
the Patuxent Wildlife Research Center have analyzed all
the dead bald eagles they could get. In a series of articles
(herein called Patuxent Eagle Papers) authored by several
researchers, about 6 percent to 8 percentofthe bald eagle
deaths were due to transmission lines. At least twice as
many were shot.
However, these sorts of calculations do not tell the
whole story for three reasons. First, fatalities and injuries
are inadequately reported. Second, a number of species
may have higher death rates that, because of their small
populations, do not show in these data but, because of
their small numbers, are nonetheless important. Third,
some species are more biologically sensitive at specific
places and seasons.
Before continuing with these points in detail, I want to
describe two kinds of significance: biological and political.
Biologists generally think in terms of birth rates, death
rates, population growth rates, carrying capacity, and so
on. A particular form of mortality becomes important when
it affects the ability of a species to survive or maintain
itself. We use bag limits to regulate the death rate of game
species to maintain healthy populations. For example,
about one-third of all pintails are killed by hunters every
year. In the Pacific Flyway, that means hunters will kill
between 1 and 1.5 million pintails each year. They will
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Keynote Address
take home only about one-third of those because many
will die of lead poisoning and some cripples will not be re-
covered by hunters. In any case, if about a thousand pin-
tails run into a transmission line, it does not make much
difference to the survival of the species; the loss of a single
California condor or whooping crane may have consid-
erable biological significance.
Now, take those thousand dead pintails and place them
so that some hunter or environmental group finds them
and calls the governor, the police, the national guard, or
the media-that is political significance. Change the
pintails to a species with an even wider constituency, such
as Canada geese, and the political significance increases.
Game species have a greater clout in somewaysthan rare
and endangered species, even though the biological threat
to the latter is greater.
A few years ago I reviewed the literature on bird colli-
sions with various obstacles. While much of the data was
circumstantial, people reported dead, usually maimed,
birds under or near television towers, bridges, transmis-
sion lines, fences, lighted buildings, unlighted buildings,
trolleys, the Cliffs of Dover, moving vans, airplanes, steam
shovels, fire towers, roller coasters (lighted and un-
lighted), smokestacks, radar antennas, ships, grain eleva-
tors, and even a mounted horseman. There are surely
other obstacles. The amazing thing is not that there are so
many deaths or maimings but that there are so few.
The literature reports collisions for about 280 species
representing almost all taxa (penguins, for example, are
not represented). Swans, pelicans, cranes, and eagles are
reported in much greater numbers than their populations
would suggest. Either big, strikingly marked birds are
easier to find and are more noteworthy or they have more
collisions per individual. In intensive studies of television
towers, it is obvious that passerines are not immune.
At first blush, I thought that regular, intensive dead bird
searches under obstacles would reveal some reliable
information about the risk to bird populations from these
obstacles. This reasoning is particularly seductive for a lin-
ear net orfence like a transmission line.ltseemssosimple
to walk along under the lines looking for downed birds.
7
Daniel E. Willard
Most birds that strike a powerline do not fall directly be-
neath it and do not get counted, however. The majority fly
off and at some distance from the line either recover or die.
Althouth I have no evidence, I suspect the crippling and
recovery rates vary with the nature of the I i ne, species, and
behavior at the time. I have seen a number of such bird col-
lisions with -lines and have never seen a bird come down,
which leads me to -believe proportionally much greater
numbers hit and run. There is no way I know to estimate
what happens to these birds.
Assuming there is a deaabirdsomewi::H~r~:oPrC>bt:~bly no
-one leeks for it. -(Whrle the literature tells us there is an
agency which records the falling of each sparrow, that
agency has not seen fit to make its/his/her data available
tome.) It issafetosay mostnongamebirddeaths are unre-
corded. Again, I cannot quantify further.
Suppose someone looks. What are the odds he will find
a bird in the area he searches? Bill Anderson's paper (in
press) is most revealing. Dogs increase the likelihood of
finding downed birds. Anderson also used boats and an
organized search team. However, when tested against
planted birds, his crew found only 58 percent of the birds.
Depending on the terrain and size and coloration of the
birds, I suspect discovery would vary considerably.
While the I iterature is replete with reports of dead birds
under lines, it is _not always -Clear how the -birds died.
Unfortunately, in our Oregon study (Willard and Willard in
press), waterfowl chose to succumb to lead poisoning,
botulism, shot wounds, and other undetermined causes
under our study lines.
Our studies did not show, nor is there literature that
indicates, whether removal by scavengers is an important
factor. In summary, so far it appears that dead bird studies,
even of game species, are inconclusive enough to limit
their usefulness as predictive tools.
I mentioned above that some species have such a small
population that the absolute number of deaths may be
small but highly important to the particular population.
Louise Young (1975) reported on the powerline induced
deaths of30 mute swans over 15years. This population on
the Jordan River in Michigan has dropped from 70 to 25
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Keynote Address
since 1959. Two birds per year could make a difference in
such a small popula~ion. In this species, not ~id~ly spread
in North America, death becomes dpubly critical.
In the Klamath Valley ofOregon we found that 1 0,000
of the world's 40,000 Ross's geese passed through one of
the alternative routes (Willard, Harris, and Jaeger 1 977).
We were forced to evaluate whether it was worse to
threaten 10,000 Ross's geese or, alternatively, 3 million
pintails. Although we wereabletoavoidboth, the question
remains. Can we really compare the value of individuals of
one ·species with the value of individuals of a nether? Is this
really c:1 biological question?
This experience suggests to me that we should take
guidance from the new strip mining legislation. This
statute requires that federal, state, and local agencies list
areas of such ecological significance that strip mining
should be forever prohibited. We might set aside buffer
zones around areas of ecological importance to avian
populations so that all presumptively detrimental impacts
would be forever prohibited. Onevehiclernight be the Rare
and Endangered" Species Act. Obvious suggestions are in
the localities of the Arkansas National Refuge (whooping
cranes), Red Rock Lake (trumpeter swans), Lake Okee-
chobee (Everglade kites), and the Los Padres National
Forest (condors).
Some species are more in jeopardy during the breed-
ing season when their population can least afford it. About
200 pairs of white pelicans breed on the Lower Klamath
Lake Wildlife Refuge. Raising a brood requires both par-
ents to forage extensively. The pelicans fly along the
canals about30feet high. While white pelicans do not dive
into the water like brown pelicans, they do watch the
water, locate prey, land, and fish. As they watch the water
while flying, they are distracted and run into lines cross-
ing the canals. During the 1976 breeding season, four
adult female pelicans were found dea9 under wires.
Autopsy showed wires were a likely cause of death. Four
out of 200 pairs were unsuccessful in raising young. A 2-
percent res:tuction is significant in a small, otherwise
threatened population. We see, then, that some species
have more significance than others and that certain times
9
Daniel E. Willard
and places are more important than others.
Where do we stand predictively? We know some things
and we do not know some others. Anderson (in press) lists
at least five factors which influence the frequency of
waterfowl collisions with powerlines:
1. Number of birds present
2. Visibility
3. Species composition or behavior of birds
4. Disturbance
5. Familiarity of birds with the area
We know how to count birds in the area. It may take
time but it can be done; in fact, in many cases it is being
done. Our method in Oregon will give us accurate data on
where and how high birds will move in an area. We know
enough to predict changes in bird movements in response
to land use changes in our area.
We know less about visibility. Stout and Cornwell
(1976), Krapu (1974), Johnsgard* and others agree that
the worst cases occur when visibility is obscured. There-
fore, Kroodsma (1977) and others have suggested mark-
ing wires in some manner. Young (1975) points out that
marking wires did not reduce the killing of mute swans. My
own studies are similar to Anderson's (in press) in that
birds seem to be able to avoid any wire they see, and birds
have good vision (except swans, perhaps) They get into
trouble when they are preoccupied with landing, other
members of their own species, and most of all predators,
or, like the pelicans, with hunting. Waterfowl, partic-
ularly, panic with the sudden appearance of an airborne
predator. In short, like humans, birds will run into things
when they are not watching where they are going.
Species vary in adeptness at avoiding lines. None
seems immune. Swans and pelicans seem particularly
vulnerable, but this may be a result oft heir detectability as
corpses.
Disturbance seems important. We can calculate the
probability of a disturbance within broad limits: we cannot
be sure when it will occur. It appears that many kills occur
when large numbers of birds are surprised in conditions of
*Paul Johnsgard 1977: personal communication.
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Keynote Address
poor visibility. In Oregon, waterfowl move about and feed
at night to avoid hunters. Because only a few fields are
optimum foraging areas at any one time, the birds gather
in only a few special fields. There theyeatquitegreedily in
huge, mixed flocks. Toward morning, fog forms. Normally,
birds will wait until visibility improves, but the hunters
come at legal dawn. Years of daily walking powerline
paths might result in a researcher's missing this worst-
case eventwhen the independent variables of farm prac-
tice,-hunting-pr-essul'e,fog,_and_disturbaoce occur.
Bird familiarity with the area is hard to calculate. In
Oregon, we found migrating birds generally flew about
300 yards high, much too high to interact with power-
lines. However, birds passed through the proposed power-
line route at least twice daily on feeding flights. During
hunting season, they crossed the "firing line" well above
shot range. On the few windy and foggy days we experi-
enced, the flocks flew about 20yards over the "firing line."
I suspect bad weather would change their normal be-
havior, even if they were familiar with the presence of
power lines.
All of this leads me to make some recommendations.
Each point is arguable depending on your relative values
for powerlines and birds.
1. Avoid ecologically sensitive areas.
2. Avoid vulnerable species.
3. Determine what it is worth to avoid sensitive
areas and vulnerable species.
4. Critically reexamine the value of devices in-
creasing the visibility of wires.
5. Control access to waterfowl areas with exist-
ing lines.
6. Study the electromagnetic effects of powerlines
on birds.
7. Assume no correlation between conductor size
and damage. (There is no evidence that 745-kv
lines are a worse impact threat than 69-kv lines.
Perhaps the converse is true.)
8. Control land use within 1 mile of new lines.
11
DanielE Willard
9. Accept dead bird studies with a certain degree
of skepticism.
REFERENCES
Anderson~ W. L. 1lnpress. Waterfowl collisions with
powerlines at a coal-fired power plant. Wildlife Society
Bull
Krapu, G. L. 1974. Avian mortality from collisions with
overhead wires in North Dakota. Fall 1972. The Prairie
Naturalist, 6(1 ).
Kroodsma, R. L. 1977. "Effects of powerlines on raptors
and waterfowl." Paper presented at A.I.B.S. Meeting,
East Lansing, Michigan. ·
Patuxent Eagle Papers
12
Coon, W. C.; Locke, L. N.; Cromartie, E; and Reichel,
W. L. 1970. Causes of bald eagle mortality 1960-1965.
J. Wildlife Diseases. 6:72-76.
Reichel, W. L.; Cromartie, E.; Lamont, T. G.; Mulhern,
B. M.; and Prouty, R. M. 1969. Pesticide residues in
eagles. Pest. Manit. J. 3.(3): 142-44.
Mulhern, B. M.; Reichel. W. L.; Locke, L. N.; Lamont,
T. G.; Belisle, A.; Cromartie, E.; Bagley, G. E.; and
Prouty, R. M. 1970. Organochlorine residues and au-
topsy data for bald eagles 1966-68. Pest. Manit. J.
4(3):141-44.
Belisle A. A.; Reichel, W. L.; Locke, L. N.; Lamont.
T. G.; Mulhern, B. M.; Prouty, R. M.; DeWolf, R. B.;
and Cromartie, E. 1972. Residues of organochlorine
pesticides, polychlorinated biphenyls and mercury
and autopsy data for bald eagles 1969 and 1970. Pest.
Manit. J. 6(3): 133-38.
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Keynote Address
Cromartie, E.; Reichel, W. L.; Locke, L. N.; Belisle,
A. A.; Kaiser, T. E.; Lamont, T. G.; Mulhern, R. M.;
Prouty, R. M.; and Swineford, D. M. Residues of or-
ganochlorine pesticides and polychlorinated biphen-
yls and autopsy data for bald eagles, 1971-1972.
Pest. Manit. J. 9( 1 ): 11-14.
Stout, J., and Cornwell, G. W. 1976. Non-hunting mor-
tality of fledged North American waterfowl. J. Wildlife
Mgt. 40(4):681-93.
Willard, D. E., and Willard, B. J. In press. Interactions of
birds and obstacles. Environ. Mgt.
Willard, D. E., Harris, J. T.; and Jaeger, M. J. 1977. The
impact of a proposed 500 KV transmission route on water-
fowl and other birds. Pub. Util. Comm., Salem, Oregon.
Young, L. B. 1975. Death trap. Nat. Wildlife. 13{2).
13
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lieynote
Response
Dale K. Fowler
Tennessee Valley Authority
Dr. Willard has done a masterful job of describing the
state of the art of this relatively new area of environ-
mental concern. I know that many of the thought provok-
ing points he has made will be vigorously debated over the
next 2 days.
I am particularly intrigued by Dr. Willard's interpre-
tation of existing wire strike mortality data.lfthis informa-
tion is relatively meaningless, then we are not in a posi-
tion to conclude that a serious problem exists. We can
speculate that more birds die from wirecollisionsthan are
found, but we can also speculate, with some support from
existing data, that the number of dead birds in the vicinity
of transmission lines reflects a low incidence of fatal colli-
sions. The magnitude of the problem (or the lack of one) is a
function of the number of dead birds. Are these collision-
related deaths frequent enough to justify the added trans-
mission line construction costs that some of Dr. Willard's
recommendations would require? Good mortality data is a
prerequisite to answering this question.
Dr. Willard's comments regarding species with
dangerously low populations are well taken. Any added
source of mortality would be a blow to such populations,
15
Dale K. Fowler
and measures to reduce the likelihood of wire strikes to
these species should be weighed heavily against all the
other factors that are considered when siting and con-
structing new lines. However, I would expect that potenti-
ally serious, collision-related situations such as proximity
to threatened and endangered species habitats would be
localized, highly site-specific, have a predictable distribu-
tion, and include only small portions of a given power
system. I a I so suspect that ~he potential for such problems
would vary among power systems due to differences in
land use, height of vegetation, topography, climate, and
other factors that would affect avian flight patterns. There-
fore, mortalities for one region, such as the West, may not
be representative of other regions, such as the Northeast
or Southeast.
We know of very few documented bird collisions with
TVA transmission lines. Occasionally we receive reliable
reports that large birds, such as great blue herons, have
been found dead beneath our lines, so collisions do occur.
However, these.rep'orts are infrequent, and there has been
no feedback from our biologists, from biologists of other
agencies, or from the general public to indicate the
existence of a serious problem.
Although we do not consider lVA transmission lines a
significant mortal'ity factor to m igratorv bird r:>opulations,
potential bird/wire collisions are evaluated during the
siting of new l'ines. Our TVA biologists closely scrutinize
corridors· that pass· near waterfowl refuges and other
sensitive habitats, and their recommendations are con-
sidere& along with many other factors, in final route
selection:. Most potential envi'ronmental problems can be
iderlt'itied' and' re·solved duri'ng transmission fine siting.
However, there are many interestg-roups to be considered
in final route selection and the choice is seldom easy:
We realize there might be specific sites Withiri our
power system where factors could create a high prob-
ability ofbird/wirecollisions. Thereareoverf7,ooo ITliles
of transmissi'on lines within the iVA system, and
obviously one cannot be absofutely sure about the
likelihood of site-sp·ecific problems being absent or pres-
ent. However, ithasb·eeri our experierice:thatwhereTvA-
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Keynote. Response
related environmental problems do·occur, there is little
time lag between the occurrence ofthe problem and our
attention being drawn to it.
If we do•have areas within the TVApower·system that
conStitute significant wire strike mortality problems, we
want to know where they are. Professionals in a diverse
arrayofdisciplinesareemployedbyTVA,andtheagencyis
involved in many natural resource programs. Among
these is a very promising cooperative.program, involving
several other agencies, aimed at establishing resident
flocksofgiantCanadageeseintheTennesseeValley.·Wire
strike mortalities involving these geese, o·r some ofthe
other water and shorebirds we are working with, would
not be welcome news to our waterfowl biologists.
'We are conducting research to better understand the
environmental effects associated with TVA's right-of-way
construction and maintenance programs. We also have a
cooperative, cost-sharing program available for land-
owners who are interested in managing wildlife onTVA
rights-of-way on their land. Although these efforts do not
directly pertain tothisworkshop,they illustratethatwhere
problems related to transmission line and opportunities
have been clearly identified, TV A has been responsive. We
intend to do thesameinthe areaofwirestrikes if a serious
:problem is quantitatively documented.
We do feel that this workshop will greatly clarify the
present confusion concerning avian mortalities asso-
Ciated with transmission lines. Many utilities are under-
standably apprehensive about economic ramifications of
, ·this relatively recent environmental consideration. A
logical, objective evaluation of this· situation· is· clearly
needed.
17
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Keynote
Response
Spencer Amend
Kansas Forestry, Fish, and Game Commission
Approximately 1 year ago [January 1977], Lawrence
Livermore Laboratory sponsored a gathering similar to this
one in an attempt to identify potential environmental
hazards associated with geothermal development. Shortly
after that meeting Ken Hoover [U. S. Fish and Wildlife
Service] and I, as well as some others, discussed the possi-
bility of using this approach to identify and, ih an orderly
manner, establish priorities for efforts at obtaining
information we do not have concerning the relationships
between power lines and bird movement patterns. So I feel
some sense of satisfaction in the fact that we are gathered
for this purpose today.
When we were initially considering an appropriate
composition for this workshop, we agreed to be guided by
the level of professional expertise of those we would
invite; that is, for the moment we are not representing
those who happen to be paying your salaries. A critical-
factor in determining our final success will be the degree
to which each of us approaches this problem on a strictly
professional and scientific basis.
Perhaps just a brief comment is in order concerning my
perception of the role of a rev~ewer in a situation such as
19
Spencer Amend
this. :I feel it is appropriate for someone in this position to
identity 'potentiaily controversial areas in order that sub-
sequefkdiscussion can focus on and clarify those areas.
· I suggest that there is a very basic question which
n¢eds to 'be addressed: "Just why are we interested in
birdsanyWayl" My answer isbased on that firstwildlife
text, to which Dr. Willard referred, specifically the part
about man's having dominion over the creatures of the
sea, land, and air.ISuggest that indeed the puq:>osefor our
·lnterestirrbirds relatestoourdesireto enjoy and use them
fdr our oWn purposes, both consumptive and rioncon-
SLimptive. 'Indeed, the entire science of Wildlife manage-
mel1tis·predicatedon the notion of manipulating wildlife
populations for man's enjoyment. This brings rne to my
first poirh of issue with Dr. Willard. He states that the
question turns on the importance or the value of the
·fatalities involved. A more accurate statement would
en'cornpass the importance relative to our abilities to
manage and subsequently toenjoythebirdsinvolved.Ap-
parently, both Or. Willard and Dale Fowler missed the
:prindpalpoint -atieasttminmyperspective -bYfocus-
ing'thelr att~rition solelyonthe cbiilsion aspect and, rriore
irnporfantly.~byoverlobkingtheirripactthroughhabitatuse
or' behavioral changes on man's use of the bird resource.
'I concurwith theapproach of recognizi11gtheimpotta11t
distihctionbetweenbiologlcal and political significance in
·discussing powerline/bird interaction. Biological signifi-
cance, 'while no doubt. an overall issue. of cbl1sider'able
importal1ce, is, !think, not likely tobe derno11strable in
reiatlon toa'single pow~rlirie, except in rarecases. The
curnt.Jiative·effect of many lines in many locations within
the areas traversed by birds throughout their life cycles
'may be of. greater significance when considered along
with other modality factors. The 'slie 'of the Species
population in question really serves' ollly'to•lncrease·the
·significance. .
'file l'le>h poi iit I wouid: l'ike to deahivith: briefly is the
Scavenging issue raised'b~tbr. Willard wheh he indicated
there is , no _literature-indicMing 'tt1at __ removal by sca-
'vengers is an irri portal'lt factor. My owl1 recolleCtion On this
polrit ''is somewhat haz'y;. perhaps thEr cornputerbibllag-
'20
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Keynote Response
raphy can help clarify this point. As with many issues, I
suspect we will need to consider this one on a rather site-
specific geographical basis, and it is reasonable to expect
considerable variation.
Dr. Willard raised the question of whether we can
really compare the value of individuals of one species With
the value of individuals of another and implied that we
would not wish to do so. I submit, however, that this is
quite a common and very realistic management question,
one which is often dealt with in setting priorities and
determining how best to direct our attention or to utilize'
our scarce resources.
I would like to endorse, for discussion purposes at
least, the suggestion that geographical areas be
inventoried from the standpoint of their sensitivities to
adverse impacts of powerlines. This kind of inventory
should be quite useful iri not only allowing powerline con~
struction to avoid highly sensitive areas but also helping
resource agencies focus data gathering efforts.
In considering Dan's nine recommendations, lfeelabit
inadequate in that no additional ones occur to me. 1· am
particularly pleased with the recom'mendation· concerri'-
ing land use· within 1 mileof new lines, although this does
not appear to follow from the logic developed in the paper.
It arises generally and Speaks to the' point I made eallier
about habitat use and availability.
In conclusion, I believe Dan gave us a g'ood keynote
speech which identifies several potential points of discus-
sion, and I look forward to attempting to resolve with you
anY conflicts I may have been able to g'enerate:
21'
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Migratory Behavior and
Flight Patterns
Sidney A. Gauthreaux, Jr.
Clemson University
INTRODUCTION
Since the beginning of recorded history the migration
of birds has attracted the attention, and intrigued the
imagination, of man. Bird migration has likewise been of
considerable interest to biologists, and myriad studies
have sought answers to the how's and why's of bird migra-
tion. Many of these studies have been summarized in
books devoted entirely to the subject (e.g., Brewster 1886,
Clarke 1912, Coward 1912, Cooke 1915, Thomson 1926,
Wetmore 1926, Tinbergen 1949, Rudebeck 1950, Lincoln
1952, Dorst 1962, Schi.iz 1971, Bykhovskii 1974, Griffin
1974). The amount of data that have been collected and
the published findings on all aspects of bird migration is
truly staggering, and even the most comprehensive re-
views have been able to provide little more than a sketchy
overview of the subject.
In this paper I will review some facts about bird migra-
tion with an emphasis on the geographical distribution of
migrants; the seasonal and daily timing of migration; the
direction, route, and altitude of migratory flights; and the
influence of weather on the density of migration. This
23
Sidney A. Gauthreaux, Jr.
information will permit a better appreciation of the
potential impact of transmission lines on all kinds of
migratory birds. Although we cannot say what this impact
is because of the lack of carefully designed, quantitative
studies, reports of bird fatalities at TV towers, tall build-
ings, and the like during migration suggest that on certain
occasions the impact could be considerable.
GEOGRAPHICAL DISTRIBUTION OF MIGRANTS
A wealth of information on the distribution of North
American migrant birds can be gleaned from the pages of
American Birds (formerly Audubon Field Notes) and the
range maps of Robbins et al. (1966). Additional informa-
tion on the geographical pattern of the breeding density of
certain migrant species can be obtained from the "Breed-
ing Bird Survey of the United States Fish and Wildlife
Service." MacArthur (1959) analyzed the breeding
distribution of North American passerines wintering pri-
marily in the neotropics (Figure 1 ). He found that the
eastern deciduous forests contained far more neotropical
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Figure 1. The distribution of the percentages of bird species breeding
in the United States but overwintering in the neotropics. Note that the
eastern third of the country contains the greatest percentages of neo-
tropical migrants (after MacArthur 1959).
24
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Migratory Behavior and Flight Patterns
migrants than northern coniferous forests and grass-
lands, and he correlated these differences vyitb the con-
trast between winter and summer food supplies in the
given habitat. Willson (1976) in a partial reanalysis of
MacArthur's (1959) findings showed that
1. North American neotropical migrants are less
prevalent in grasslands than in forests, but
there is no significant difference in the propor-
tion of neotropical migrants in deciduous and
coniferous forests.
2. Coniferous forests have relatively fewer year-
round resident individuals than grasslands or
deciduous forests, and grasslands and conifer-
ous forests have slightly fewer resident species
than deciduous forests.
3. Most neotropical migrant birds breed primarily
in deciduous forests, and most of those that
breed in coniferous forests are parulids (e.g.,
American warblers).
In the northeastern deciduous forests, on the average
62 percent of the breeding species and 75 percent of the
individuals are migrants. In the northern coniferous for-
ests 80 percent of the breeding species and 94 percent of
the individuals are migrants, while in the grasslands 76
percent of the breeding species and 73 percent of the
individuals are migrants. Although similar analyses for
waterfowl and shorebirds are not available, distribution
and migration data can be found in Bellrose (1976) and
Palmer (1976) for waterfowl and in Stout et al. (1968) and
Sanderson (1977) for shorebirds.
In general there is considerably more bird migration in
the eastern two-thirds of the United States than in the
West (Lowery 1951; Lowery and Newman 1955, 1966).
One basis for this pattern is that more migrants (species
and individuals) breed in the East, but another basis is
exemplified in Figure 2. The breeding range of the Phil-
adelphia vireo extends toward the northwest into Canada,
but its migration is restricted to the eastern United States.
Approximately 33 species of land bird migrants conform to
this pattern. Thus, even though a number of land bird
25
Sidney A. Gauthreaux, Jr.
60
50
40
30
20
10
120° 1100 1000 goo 80° 70°
Figure 2. The breeding distribution and migration area of the Phil-
adelphia Vireo (Vireo philade/phicus). Although the breeding range of
this species extends into northwestern Canada, its migration through
the United States is confined to the eastern half of the country (after
Robbins et al. 1966).
migrants breed considerably farther west and north of the
eastern forests of the United States, they migrate through
the eastern states. The white-throated sparrow is an
example of a short-distance migrant that winters in the
26
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Migratory Behavior and Flight Patterns
southern portions of the United States (Figure 3). Even
though the breeding and wintering ranges extend west-
ward, the spring and fall migration ofthe species is almost
exclusively east of the Rocky Mountains.
50
40
20
120° 110° 100° goo ao 0 70°
Figure 3. The breeding and wintering distribution of the white·
throated sparrow (Zonotrichia albicollis) in North America. Although
the breeding range and wintering range of this species extend beyond
120°W, the species migrates almost exclusively to the east of the Rocky
Mountains (after Robbins et al. 1966),
27
Sidney A. Gauthreaux, Jr.
SEASONAL TIMING
Much of what we know about the seasonal timing of
bird migration in North America comes from the work of
field observers and birdbanders, and their findings have
been regularly summarized in the spring and fall migra-
tion issues of American Birds. Virtually every state has a
checklist or bird book containing information on the
seasonal occurrences of migrant birds. Saunders (1959)
examined the variation in the timing of spring arrivals
among 50 different species in comparison with the mean
40-year arrival dates and found that in late, cold springs
migrants arrived later than in early, warm springs.
Gauthreaux and LeGrand (1975) associated the advance-
ment or retardation of the seasonal timing of migration
with year-to-year changes in continental wind patterns.
Robbins et al. (1966) has summarized considerable data
on the seasonal timing of bird migration for most North
American species. This information is presented on
species maps as isochronal lines that show the average
first-arrival date where birds migrating to the north maybe
seen about the first of March, April, May, and June.
Preston (1966) has analyzed mathematically the timing of
spring and fall migration arid found that in general those
species that go early return late (e.g~. waterfowl,
sparrows). Preston discusses evidence that shows breed-
ing birds occupy their summer habitat as soon as it is
habitable and depart as soon as they have finished breed-
ing. The standard deviation of the timing of a species'
migration is less in spring than in fall, hence the birds are
better synchronized in spring. During fall migration some
species show an almost bimodal timing with young and
adults traveling at somewhat different times (see Murray
1966). In the spring, males of most species arrive before
the females, and adults precede young (Gauthreaux
1978a).
A number of factors must be considered in discussing
the seasonal timing of migration. The more important of
these are vegetational development in the spring, food
availability, and climatic factors in spring and fall. Weyde-
meyer (1973), in a 48-year study of spring arrivals of
28
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Migratory Behavior and Flight Patterns
migrants in Montana, found that ranges in dates of arrival
were greatest during late March and April and least in late
May and June. Slagsvold ( 1976) Working in Norway found
that for the country as a whole there was a 6-day delay in
bird arrival for each 1 0-day delay in vegetation develop-
ment. Thus, the arrival of migrants at higher latitudes and
altitudes was faster than the development of vegetation.
Slagsvold also found that earlier arriving species varied
considerably in arrival date at a particular locality from
year to year, but late arriving species had much less vari-
ation in arrival time. Pinkowski and Bajorek (1976)
examined the spring arrival dates of 29 common or con-
spicuous migrants and summer resident species in
southern Michigan over a 7-year period. They concluded
that granivorous, omnivorous, and aquatic species tend to
arrive earlier than strictly insectivorous species, and that
earlier arriving species have a greater variance in arrival
time than the later arriving species.
DAILY TIMING OF MIGRATION
The majority of small birds, including most passerines,
migrate at night, and most waterfowl and shorebirds
migrate both at night and during the day. Raptors, several
woodpeckers, swallows, several corvids, bluebirds, and
blackbirds migrate during daylight hours. The determina-
tion of whether a species migrates at night or during the
day has come from laboratory studies of Zugunruhe-
migratory restlessness in caged birds (Gwinner 1975);
from data gathered when migrating birds collide with TV
towers, buildings, or powerlines or when migrants are
attracted to, and killed at, lighthouses and ceilometers (see
Weir 1977 for review); and from direct visual studies of
daytime migration in progress. According to data gathered
by surveillance radars at several localities in the United
States and Canada, considerably more birds migrate at
night than during the day (Gauthreaux 1975).
A number of studies have shown the temporal pattern
of nocturnal migration (e.g., Lowery 1951, Sutter 1957a,
Harper 1958, Gauthreaux 1971 ). As can be seen in
Figure 4, the initiation of nocturnal migration occurs about
30 to 45 minutes after sunset; the number of migrants
29
Sidney A. Gauthreaux, Jr.
100
90
80
70
~ 60
ell
i 50 ~ u ...
:. 40
30
20
10
1800 2000 2200 2400 0200 0400
Time (CST)
Figure 4. The average hour-to-hour variation in the quantity of noc-
turnal migration plotted as the percentage of peak density. The data for
8 nights were gathered using WSR-57 weather radar during the spring of
1965 in southwestern Louisiana (see Gauthreaux 1971 for more
details).
aloft increases rapidly, peaking between 2200 and 2300
hours. Thereafter, the number of migrants aloft decreases
steadily until dawn, indicating that migrants are landing at
night. Daytime migration is initiated near dawn (some-
times earlier), peaks around 1000 hours, and declines to
minimal density shortly after noon (Sutter 1957b, Gehring
1963, Gauthreaux 1978b).
DIRECTIONS AND ROUTES OF BIRD MIGRATION
Although considerable attention has been directed to
laboratory studies of direction finding in migratory birds
(Emlen 1975), there is an increasing emphasis on field
studies of migratory orientation using direct visual means
(Lowery 1951, Lowery and Newman 1963, Gauthreaux
1969) and radar (Eastwood 1967, .Gauthreaux 1975).
30
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Migratory Behavior and Flight Patterns
Radar can provide detailed information on the direction of
migratory movements when conditions for direct visual
studies are poor while at the same time sample a fairly
large geographical area. Figure 5 is a photograph of the
display of the ASR-4 radar operated by the Federal Avia-
tion Administration at the Greenville-Spartanburg Airport
in northwestern South Carolina. Similar radar systems are
operated at many medium-sized and large airports
throughout the United States. Echoes from individual
birds can be seen moving toward the north-northeast.
Movement is indicated by the "tails" of echoes produced
by the fading of previously registered echoes.
Radar studies of bird migration have been conducted in
Illinois (Graber and Hassler 1962, Bellrose and Graber
1963, Hassler et al. 1'963, Bellrose 1964, Graber 1968),
coastal New ~ngland (Drury and Keith 1962, Nisbet
1963a, Drury and Nisbet 1964, Nisbet and Drury 1968),
Figure 5. A photograph of the ASR-.lJ. radar screen showing echoes
from birds migrating toward the NNE. The range marks are located
every 2 nautical miles. Echoes from aircraft appear near 6 nm range at
80° and 10° azimuths. The photograph was made on 27 April1972 at
Greenville, South Carolina (Federal Aviation Administration ASR-4
radar installation), at 1947 EST.
31
Sidney A. Gauthreaux, Jr.
eastern New Jersey (Swinebroad 1964), coastal Virginia
(Williams et al. 1972, 1977), in South Carolina (Gauthr-
eaux 1974, 1976, 1978b), northern Georgia (Gauthreaux
and Able 1970; Able 1973, 1974; Gauthreaux in prep.),
coastal Louisiana (Gauthreaux 1971, 1972; Able 1972,
1973, 1974; Fuller 1977), in northern Ohio(Tolle and Gau-
threaux in prep.), Arizona, New Mexico, and western
Texas (Beason 1978), several locations in Canada
(Richardson 1969, 1971, 1972; Blokpoel and Defosses
1970; Myres and Cannings 1971; Richardson and Gunn
1971; Speirs et al. 1971; Blokpoel 1974; Blokpoel and
Gauthier 1974), and in northwestern Alaska (Flock 1972,
1973; Hubbard and Flock 1974). Although there are many
geographical gaps in the coverage and some studies have
concentrated on waterfowl migration (e.g., Bellrose 1964,
Blokpoel et al. 1975), particularly west of the Rocky
Mountains (Beason 1978), a continental pattern of bird
migration in North America is beginning to emerge. '
In general, the axis of migration for most passeri nes is
northeast to southwest in the eastern two-thirds of the
United States, but in central southern Canada the axis of
passerine migration is northwest to southeast. Bellrose
(1964, 1976) has shown that most waterfowl in the
Mississippi valley move more north-south with eastward
and westward deviations depending on topographic
factors (lakes, marshlands, and river systems). Wind
direction exerts a strong influence on the direction and
timing of migration (Gauthreaux and Able 1970, Able
1974, Alerstam 1976), and the routes birds fly appear to be
determined, at least in part by the prevailing wind
patterns in North America during spring and fall (Gau-
threaux 1972). For example, in northwestern South Caro-
lina in spring the prevailing winds blow to the northeast,
and the average distribution of the directions of nocturnal
migration on calm nights (that is, when wind directions are
not an influencing factor) in spring is toward the north-
east (29.5°). Thus, in spring the preferred direction of
migrants closely matches the prevailing wind direction. In
fall the winds in the same area usually blow toward the
southeast, and the average distribution of the directions of
nocturnal migration on calm nights is toward the south-
32
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Migratory Behavior and Flight Patterns
west (231.5°). These data were gathered using direct
visual means, moon-watching (Lowery 1961 ), and ceil-
ometer-watching (Gauthreaux 1969), but data gathered
from radar conform to the above pattern (see Gauthreaux
1978b for details). Wind direction in relation to the normal
direction of migration can also influence the altitude of
migration as well as the number of migrants aloft, and
these topics are discussed below.
There have been very few field studies of the influence
of powerlines or other electromagnetic devices on bird
migration, but there is some evidence that when local
magnetic fields are disrupted by electrical currents, the
orientation of birds is affected slightly (see discussions by
Southern 1975, Larkin and Sutherland 1977, Moore
1977). The magnetic disturbance produced by electrical
current in powerlines is generally localized and does not
extend beyond a distance of several meters. Thus, the
effects on the orientation of migrating birds may be
minimal when birds fly well above the powerlines, but
clearly more work is needed on this subject.
ALTITUDE OF MIGRATION
Radar has provided the best data on the altitude of bird
migration, and radar studies have shown that most bird
migration normally occurs at altitudes below 500_meters
above ground level (Nisbet 1963b; Eastwood and Rider
1965; Able 1970; Bellrose 1971; Blokpoel1971 a, 1971 b;
Bruderer and Steidinger 1972; Gauthreaux 1972). In
general, the larger the bird species and the faster its
airspeed, the higher it flies during migration for minimum
cost of transport (Tucker 1975).
The distribution of nocturnal migrants in the airspace is
strongly skewed to the lower altitudes. In Table 1 the
quantity of nocturnal migration per altitudinal stratum is
expressed as the percentage of the total number of birds
aloft. The data were gathered using WSH-57 weather
radar at New Orleans, Louisiana, in the spring of 1967 (see
Gauthreaux 1970, 1972). Seventy percent ofthe migrants
at night were most frequently between 241 meters (800
feet) and 1127 meters (3718 feet), and within this zone
approximately 75 percent were between 241 meters (800
33
Sidney A. Gauthreaux, Jr.
Table 1. Altitude of Nocturnal Migration at New Orleans ( Expressed as
Percentage of Total Number of Birds Aloft)
Antenna Elevation Altitudinal Zones in Meters
2.5° 241-1127 482-1690 724-2254 965-2817 -(N = 34) X 70 20 8 4
S.D. 19 13 10 8
(N = 30) 241-482 482-724 724-965 965-1206 -. 74 X 18 7 2
S.D. 17 14 8 3
feet) and 482 meters ( 1600 feet).l n Table 2 the altitudes of
peak densities of migrants alofton70spring nightsand35
fall nights are given. These measurements were made
with the WSR-57 radar at weather stations in New
Orleans and Lake Charles, Louisiana; Athens, Georgia;
and Charleston, South Carolina. Seventy-three percent of
Table 2. Altitude of Greatest Concentration of Nocturnal Migrants
Aloft
Altitude Number of observations
Meters Feet Spring Fall
152 500
305 1000 57 22
457 1500 3 2
610 2000 6 3
762 2500 2
914 3000
1219 4000 2
1372 4500 3
1524 5000 1 3
1676 5500 1 2
1829 6000 2 2
2134 7000
2286 7500
Total 79 39 -.-
34
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Migratory Behavior and Flight Patterns
the 79altitude measurements on 70spring nights showed
the altitudes of peak densities of migrants to be at 305
meters or lower. In the fall 56 percent of the 39
measurements on 35 nights indicated that the greatest
concentrations of migrants aloft were at 305 meters. As
Table 2 shows, on some occasions the altitude at which
most birds were migrating was considerably higher than
the usual 305 meters.
Most radar cannot detect birds very close to the ground
(but some shipboard navigation radar can), and conse-
quently the minimum altitude of nocturnal migration
displayed on "radar cannot be measured accurately.
Studies using direct visual means to detect migrating birds
as they pass through a narrow vertical beam of light
(Gauthreaux 1969) suggest that a considerable number of
birds fly within 100 meters of the ground at night. This is
particularly so within an hour after the initiation of
nocturnal migration and at the time birds are landing
during the night. On some misty, cloudy nights
tremendous numbers of call notes from migrants aloft can
be heard, and on many of these occasions the distance of
the call notes overhead indicates the birds are flying
within a few meters of the ground. The altitude of migra-
tion changes throughout the night. Usually the maximum
mean altitude of migration is reached about 2 hours after
the initiation and thereafter slowly declines as birds begin
to terminate their nightly migration (Able 1970).
Daytime migration u~ually occurs at altitudes below
300 meters, and quite oftenflocksofdaytime migrants can
be seen moving just above tree level. This, however, is not
always the case. When migrants are arriving on the
northern coast of the Gulf of Mexico during daylight hours
in spring after a trans-Gulf flight, they are usually at
altitudes above 1500 meters (Gauthreaux 1971, 1972).
When the migrants encounter a cold front and headwinds
before they make their landfall, they will often fly within a
few meters of the water's surface. On these occasions
when the flights are delayed and most of the migrants
arrive at night, tremendous numbers will strike wires,
towers, and the like. In general, daytime migrants will fly
lower when there is poor visibility, dense cloud cover, and
drizzle.
35
Sidney A. Gauthreaux, Jr.
WEATHER INFLUENCES ON THE
DENSITY OF MIGRATION
Figure 6 shows the radar displays of nocturnal
migration on ASR-4 radar with different migration traffic
rates (Gauthreaux 1978b). Thesedisplayswerequantified
by direct visual means (moon-watching [Lowery 1951] and
ceilometer observations [Gauthreaux 1969, Able and
Gauthreaux 1975]). Once calibrated, the radar can be used
to measure the quantity of migration, and it is possible to
study the weather factors responsible for the different
night-to-night variat.ion in the quantity of migration. It is
generally accepted that in spring more migration occurs
on the west side of a high pressure system and before a
cold front and low pressure system (zones 4 and 5 in
-Figure 7). In fall very large migrations occur just after a
cold front on the east side of a high pressure system (zones
1 and 2 in Figure 7). Butwhatweatherfactorsorcombina-
tion of weather factors influence the density of migration?
In the last several years a number of studies have
attempted to answer this question (see Richardson 1978
for a detailed review of this subject). Because weather
factors interact in complex ways, multivariate statistical
analyses must be used, and the results of studies using
such analyses have been summarized in Tables 3 and 4.
Table 3 gives the weather factors that have been shown to
significantly influence the quantity of spring migration. Of
all the weather factors listed. wind and temperature are
clearly the most consistently important factors. In fall
Figure 6. Photographs of the ASR-4 radar screen showing the changes
in the density of bird echoes as a function of migration traffic rate
(the number of birds crossing 1 mile of front per hour). All photo-
graphs were made with the radar adjusted to 6 nautical mile range, the
same high gain setting, Moving Target Indicator (MTI) engaged, and no
attenuation circuits engaged. As can be seen, once the traffic rate (TR)
is about 30,000 birds, the screen is essentially saturated with bird
echoes. (A) 9 May 1977, TR = 2000; (B) 12 May 1977, TR = 5000; (C)
24 April 1977, TR = 10,400; (D) 21 April 1977, TR = 12,000; (E) 28
April 1977, TR = 21,600; (F) 11 May 1977, TR = 32,400; (G) 26
September 1977, TR = 52,000; (H) 28 September 1977, TR = 218,700.
36
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Figure 7. A generalized synoptic weather pattern showing zones used
in analyzing the relationship between synoptic weather and the density
of bird migration in spring and fall. The arrows indicate the general pat-
tern of airflow.
(Table 4) the same pattern is found. Both wind and
temperature are, of course, significantly intercorrelated.
Thus, the largest spring migrations occur with winds from
the south and southwest, which bring warming tempera-
tures, and the largest fall migrations occur with winds
from the northwest and north, which usually bring colder
temperatures to an area. Another point regarding the
influence of weather on the quantity of bird migration
should be mentioned. The amount of night-to-night varia-
tion in thequantityof migration explained by weather is 50
percent to 60 percent on the average. The remaining varia-
tion is undoubtedly due to the internal conditions of the
38
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Table 3. Influence of Weather Variables on Spring Migration (Multivariate Analyses)
General Weather Variables8
Relative Barometric General R2 or
Temperature Wind Cloud Humidity Pressure Precipitation Weather Rc2
Lack (1960) * * * *
Lack ( 1963b) * * * *
Nisbet and Drury (1968) * * * * * 0.60
Richardson (1971, 1974b) * * * 0.62
Geil et al. (1974)b * * * * 0.61
Geil et al. (1974)c * * * * 0.43
Richardson (1974a)d * * 0.51
Richardson (1974a)e * 0.40
Alerstam ( 1976) * * * * 0.44
Gauthreaux (1976) * * * * 0.54
8 Specific weather variables (e.g., 24-hour change in temperature, temperature departure from normal) are included in general
variable (e.g., temperature).
bMarch.
cApril.
doffshore.
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Table 4. Influence of Weather Variables on Fall Migration (Multivariate Analyses)
Temp Wind
Lack ( 1963a)b *
Lack ( 1963a)c * *
Able (1973) * *
Geil et al. (1974)b * *
Geil et al. ( 1974)d *
Richardson (1974b) * *
Alerstam (1976) * *
Richardson ( 1976) *
Bruderer (1978) *
Cloud Visibility
*
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General Weather Variables8
Relative
Humidity
*
*
*
Barometric
Pressure Precipitation
*
* *
*
*
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General Magnetic
Weather Disturbance
*
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R2 or
Rc2
0.54
0.44
0.48
0.51
0.61
0.26
0.52
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variable (e.g., temperature).
bSeptember.
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Migratory Behavior and Flight Patterns
migrants (e.g., energy for migration, physiological readi-
ness to niigrate)andthe actual number of ground migrants
in an area.
The weather conditions most often associated with
migrants colliding with man-made objects (poor visibility,
low ceiling, drizzle) are not those conducive to very large
migratory movements. Why, then, do tremendous
numbers of migrants collide with TV tower guylines, build-
ings, and other obstructions during migration? The answer
to this question is rather straightforward. When birds
initiate a migration with favorable weather conditions,
they sometimes move into areas where the weather has
deteriorated (e.g., a stalled frontal system), and this
combination of events is usually associated with such dis-
asters. Occasionally disasters occur under ideal weather
conditions for migration, but these are exceptional (Avery
et al. 1977).
ACKNOWLEDGMENTS
wish to acknowledge the personnel of the United
States Weather Bureau and the Federal Aviation Admini-
stration for their generous cooperation in permitting me to
use their radar systems during my bird migration work. I
also wish to acknowledge the continued grant support of
the Air Force Office of Scientific Research for my ongoing
research program in bird migration. The manuscript was
brought into final form while I held grantAFOSR 75-2782,
and I thank Anne Snider and Frank Moore for their assist-
ance in the preparation of the manuscript.
REFERENCES
Able, K. P. 1970. A radar study of the altitude of nocturnal
passerine migration. Bird-Banding 41 (4):282-90.
Able, K. P. 1972. Fall migration in coastal Louisiana and
the evolution of migration patterns in the Gulf region.
Wilson Bull. 84 (3):231-42.
Able, K. P. 1973. The role of weather variables and flight
direction in determining the magnitude of nocturnal bird
migration. Ecology 54(5): 1031-41.
41
Sidney A. Gauthreaux, Jr.
Able, K. P. 1974. Environmental influences in the orienta-
tion of free-flying nocturnal bird migrants. Anim. Behav.
22(1 ):224-38.
Able, K. P. and Gauthreaux, Jr., S. A. 1975. Quantifica-
tion of nocturnal passerine migration with a portable ceil-
ometer. Condor 77(1 ):92-96.
Alerstam, T. 1976. "Bird migration in relation to wind and
topography." Thesis, University of Lund, Sweden. 51 pp.
Avery, M,; Springer, P. F.; andCasseii,J. F. 1977. Weather
influences on nocturnal bird mortality at a North Dakota
tower. Wilson Bull. 89(2):291-99.
Beason, R. C. 1978. The influences of weather and topog-
raphy on water bird migration in the southwestern United
States. Oecologia 32(2): 1 53-70.
Bell rose, F. C. 1964. Radar studies of waterfowl migration.
In Trans. 29th N. Amer. Wild/. Conf.:128-43.
Bell rose, F. C. 1971. The distribution of nocturnal migrants
in the air space. Auk 88:397-424.
Bellrose, F. C. 1976. Ducks. Geese and Swans of North
America. Harrisburg, Pennsylvania: Stackpole.
Bell rose, F. C. and Graber, R. R. 1963. A radar study of the
flight directions of nocturnal migrants. In Proc. 13th Int.
Omit hoi. Con gr. :362-89.
Blokpoel, H. 1971 a. The M33C track radar (3-cm) as a tool
to study height and density of bird migration. Studies of
Bird Hazards to Aircraft. Canad. Wildl. Serv. Rep. Ser. No.
14:77-94.
B•~~J.noel, H. 1971 b. A preliminary study on height and
.sity of nocturnal fall migration. Studies of Bird Haz-
.-~rds to Aircraft. Canad. Wildl. Serv. Rep. Ser. No. 14:95-
104.
Blokpoel, H. 1974. Migration of lesser snow and blue
geese in spring across southern Manitoba. Part 1:
Distribution, chronology, directions, numbers, heights,
and speeds. Canad. Wildl. Serv. Rep. Ser. No. 28:1-30.
42
t:
[
[
[
[
[
c
[
[
c
D
L~
E
[
[
r
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L~
[
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[
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[
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[J
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6
c
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c
[~
.J
Migratory Behavior and Flight Patterns
Blokpoel, H. and Defosses, P. P. 1970. Radar observations
of local bird movement near Calgary, Alberta. Assoc.
Comm. on Bird Hazards to Aircraft, Nat. Res. Council Field
Note 53.
Blokpoel, H. and Gauthier, M. C. 1974. Migration of lesser
snow geese in spring across southern Manitoba. Part II: In-
fluence of the weather and prediction of major flights.
Canad. Wildl. Serv. Rep. Ser. No. 32:1-30.
Blokpoel, H,; Heyland, J. D.; Burton, J.; and Samson, N.
1975. Observations on the fall migration of greater snow
geese across southern Quebec. Canad. Field-Nat.
89(3):268-77.
Brewster, W. 1886. Bird migration. Mem. Nuttal Ornith.
Club, No. 1.
Bruderer, B. 1978. Weather-dependence of height, den-
sity and direction of migration in Switzerland. In Proc. 3rd
World Cont. Bird Hazards to Aircraft. Paris, France, 25-28
October 1977.
Bruderer, B. and Steidinger, P. 1972. Methods of quanti-
tative and qualitative analysis of bird migration with track-
ing radar. In Symp.· Animal Orientation and Navigation,
Wallops Island, Virginia, pp. 151-67.
Bykhovskii, B. E., ed. 1974. Bird Migration: Ecological and
Physiological Factors. New York: John Wiley.
Clarke, W. E. 1912. Studies· in Bird Migration. 2 vols.
London: Gurney and Jackson.
Cooke, W. W. 1915. Bird Migration. U.S. Dept. Agric. Bull,
No. 185.
Coward, T. A. 1 912. The Migration of Birds. Cambridge,
Massachusetts: Cambridge Univ. Press.
Dorst. J. 1962. The Migration of Birds. Boston: Houghton-
Mifflin Co.
Drury, W. H. and Keith, J. A. 1962. Radar studies of song-
bird migration in eastern New England. Ibis 104:449.:89.
43
Sidney A. Gauthreaux, Jr.
Drury, W. H. and Nisbet, I. C. T. 1964. Radar studies of
orientation of songbird migrants in southeastern New
England. Bird-Banding 35:69-119.
Eastwood, E. 1967. Radar Ornithology. London: Methuen
Co.
Eastwood, E. and Rider, G. C. 1965. Some radar measure-
ments of the altitude of bird flight. Brit. Birds 58:393-426.
Emlen, S. T. 1975. Migration: Orientation and navigation.
Avian Biology. D. S. Farner and J. R. King, eds., pp. 129-
219. New York: Academic Press.
Flock, W. L. 1972. Radar observations of bird migration at
Cape Prince of Wales. Arctic 25(2):83-98.
Flock, W. L. 1973. Radar observations of bird movements
along the Arctic coast of Alaska. Wilson Bull. 85(3):259-
75.
Fuller, D. A 1977. "Waterfowl migration routes into Lou-
isiana as determined by radar surveillance." M.S. thesis,
Louisiana State University, Baton Rouge, Louisiana. 45
pp.
Gauthreaux, S. A, Jr. 1969. A portable ceilometer tech-
nique for studying low-level migration. Bird-Banding
40( 4):309-20.
Gauthreaux, S. A, Jr. 1970. Weather radar quantification
of bird migration. BioScience 20( 1 ): 17-20.
Gauthreaux, S. A, Jr. 1971. A radar and direct visual study
of passerine spring migration in southern Louisiana. Auk
88(2):343-65.
Gauthreaux, S. A, Jr. 1972. Behavioral responses of mi-
grating birds to daylight and darkness: A radar and direct
visual study. Wilson Bull. 84(2): 136-48.
Gauthreaux, S. A, Jr. 1974. The detection, quantification,
and monitoring of bird movements aloft with airport sur-
veillance radar (ASR). In Proc. Con f. Biological Aspects of
the Bird I Aircraft Collision Problem, Clemson University,
Clemson, South Carolina, pp. 289-307.
44
L
[
[''
[
[
f'
c
c
[
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[
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[
L
[
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[
[
[
[
[
[
c
[
[J
D
B
[
[
[
[
Migratory Behavior and Flight Patterns
Gauthreaux, S. A., Jr. 1975. Radar Ornithology: Bird
Echoes on Weather and Airport Surveillance Radars.
Clemson, South Carolina: Clemson University.
Gauthreaux, S. A., Jr. 1976. The influence of weather vari-
ables on the density of nocturnal migration in spring.
Paper presented at the 94th Annual Meeting of the Ameri-
can Ornithologists' Union, 9-13 August 1976, Haverford,
Pennsylvania.
Gauthreaux, S. A., Jr. 1978a. The ecological significance
of behavioral dominance. In Perspectives in Ethology, vol.
3, P. P. G. Bateson and P. H. Klopfer, eds., pp. 17-54. New
York: Plenum Press.
Gauthreaux, S. A., Jr. 1978b. The importance of the day-
time flights of nocturnal migrants: Redetermined
migration following displacement. In Proc. Symp. Animal
Migration, Navigation, and Homing, Tubingen, West
Germany. New York: Springer-Verlag.
Gauthreaux, S. A., Jr. (in prep.) The orientation of pas-
serine night migrants in relation to prevailing wind
patterns in the southeastern United States.
Gauthereaux, S. A., Jr. and Able, K. P. 1970. Wind and the
direction of nocturnal songbird migration. Nature
228(5270):476-77.
Gauthreaux, S. A., Jr. and LeGrand, H. E., Jr. 1975. The
changing seasons: Spring migration 1975. Amer. Birds
29(4):820-26.
Gehring, W. 1963. Radar-und Feldbeobachtungen uber
den Verlauf des Vogelzuges in Schweizerischen
Mittleland: Der Tagzug im Herbst(1957-1961 ). Om. Beob.
60:35-68.
Geil, S.; Noer, H.; and Raboi,J. 1974. Forecast Models for
Bird Migration in Denmark. Bird Strike Committee Den-
mark, Royal Danish Air Force.
Graber, R. R. 1968. Nocturnal migration in Illinois: Differ-
ent points of view. Wilson Bull. 80:36-71.
45
Sidney A. Gauthreaux, Jr.
Graber, R. R. and Hassler, S. S. 1962. The effectiveness of
aircraft-type (APS) radar in detecting-birds. Wilson Bull.
74:367-80.
Griffin, D. R. 1974. Bird Mi9ration. New York: Dover Pub-
lications.
Gwinner, E. 1975. Circadian and circannual rhythms in
birds. In Avtan Biolog. vol. 5, D. S. Farner and J. R. King,
eds. pp. 221-85. New York: Academic Press.
Harper, W. G. 1958. Detection of birds by centrimetric
radar: A cause of radar "angels." In Pro c. Roy. Soc. Land.
Ser. B. 149:484-502.
Hassler, S. S.; Graber, R. R.; and Bellrose, F. C. 1963. Fall
migration and weather: A radar study. Wilson Bull. 75:56-
77.
Hubbard, J. and Flock, W. L. 1974. Radar Observation of
Migratory Waterfowl at Cold Bay, Alaska. AFWL-DE-TN-
008, Kirtland AFB, New Mexico.
Lack, D. 1960. Migration across the North Sea studied by
radar: Part 2, the spring departure 1956-1959. Ibis
102:26-57.
Lack, D. 1963a. Migration across the l:!OUthern North Sea
studied by radar: Part 4, autumn. Ibis 105:1-54.
Lack, D. 1963b. Migration across the southern North Sea
studied by radar: Part 5, movements in August, winter and
spring, and conclusion. Ibis 105:461-92.
Larkin, R. P., and Sutherland, P. J. 1977. Migrating birds
respond to Project Seafarer's electromagnetic field.
Science 195:777-79.
Lincoln, F. C. 1952, Migration of Birds. New York: Double-
day & Co.
Lowery, G. H., Jr. 1951. A quantitative study of the noc-
turnal migration of birds. Univ. Kansas Pub/. Mus. Nat.
Hist. 3:361-472.
46
L
[
[
[
[
[
c
E
[
D
[
E
[
L
[
L
L
[
[
[
[
[
[
C
c
E
c
b
[J
[
[
[
Migratory Behavior and Flight Patterns
Lowery, G. H., Jr. and Newman, R. J. 1955. Direct studies
of nocturnal bird migr_ation. In Recent Studies in Avian
Biology, A. Wolfson, ed., pp. 238-63, Urbana: Univ.lllinois
Press.
Lowery, G. H., Jr. and Newman, R. J. 1963. Studymg Btrd
Migration with a Telescope. Spec. Publ. Mus. Zool. Loui-
siana State Univ.
Lowery, G. H., Jr. and Newman, R. J. 1966. A continent-
wide view of bird migration on four nights in October. Auk
83:547-86. .
MacArthur, R. H. 1959. On the breeding distribution pat-
tern of North American migrant birds. Auk 76:318-25.
Moore, F. R. 1977. Geomagnetic disturbance and the ori-
entation of nocturnally migrating birds. Science 196:682-
84.
Murray, B. G., Jr. 1966. Migrationofageandsexclassesof
passerines on the Atlantic coast in autumn. Auk 83:352-
60.
Myres, M. T. and Cannings, S. R. 1971. A Canada goose
migration through the southern interior of British Col-
umbia. Studies of Bird Hazards to Aircraft. Canad. Wildl.
Serv. Rep. Ser. No. 14:23-34.
Nisbet, I. C. T. 1963a. Quantitative study of migration with
23-centimetre radar. Ibis 105:435-60.
Nisbet, I. C. T. 1963b. Measurements with radar of the
height of nocturnal migration over Cape Cod, Massachu-
setts. Bird-Banding 34:57-67.
Nisbet, I. C. T. and Drury, W. H. 1968. Short-term effects of
weather on bird migration: A field study using multi-
variate statistics. Anim. Behav. 16:496-530.
Palmer, R. S., ed. 1976. Handbook of North Amertcan
Birds, vols. 2 and 3. New Haven, Connecticut: Yale Univ.
Press.
Pinkowski, B. C. and Bajorek, R. A. 1976. Vernal migration
47
Sidney A. Gauthreaux, Jr.
patterns of certain avian species in southern Michigan.
Jack-Pine Warbler 54(2):62-68.
Preston, F. W. 1966. The mathematical representation of
migration. Ecology 47:375-92.
Richardson, W. J. 1969. Temporal variation in the volume
of bird migration: A radar study in Canada. In Pro c. World
Cont. Bird Hazards to Aircraft, Queen's Univ., Kingston,
Ontario, pp. 323-34.
Richardson, W. J. 1971. Spring migration and weather in
eastern Canada: A radar study.Amer. Birds 25(4):684-90.
Richardson, W.J. 1972.Autumn migration and weather in
eastern Canada: A radar study. Amer. Birds 26(1 ):1 0-16.
Richardson, W. J. 1974a. Spring migration over Puerto
Rico and the western Atlantic: A radar study. Ibis 116:172-
93.
Richardson, W. J. 1974b. Multivariateapproachestofore-
casting day-to-day variations in the amount of bird migra-
tion. In Proc. Con f. Bioi. Aspects Bird I Aircraft Collision
Problem, pp. 309-29. Clemson University, Clemson,
South Carolina.
Richardson, W. J. 1976. Autumn migration over Puerto
RicoandthewesternAtlantic: A radar study. Ibis 118:309-
32.
Richardson, W. J. 1978. Timin.g and amount of bird migra-
tion in relation to weather: a review. Oikos (in press).
Richardson, W. J. and Gunn, W. W. H. 1971. Radar obser-
vations of bird movements in east-central Alberta. Studies
of Bird Hazards to Aircraft. Canad. Wildl. Serv. Rep. Ser.
No. 14:35-68.
Robbins, C. S.; Bruun, B.; Zim, H. S.; and Singer,A. 1966.A
Guide to Field Identification: Birds of North America. New
York: Golden Press.
Rudebeck, G. 1950. Studies on bird migration. V~r F~gel
varld Suppl. 1 : 1-148.
48
L
[
[
[
[
[
c
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[
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L
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[
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Migratory Behavior and Flight Patterns
Sanderson, G. C., ed. 1977. Management of Migratory
Shore and Upland Game Birds in North America.
Washington, D.C.: Int. Assoc. Fish. & Wildl. Agencies.
Saunders, A. A. 1959. Forty years of spring migration in
southern Connecticut. Wilson Bull. 71:208-19.
Schuz, E. 1971. Grundriss der Vogelzugskunde. Berlin:
Paul Parey.
Slagsvold, T. 1976. Arrival of birds from spring migration
in relation to vegetational development. Norw. J. Zoo/.
24:161-73.
Southern, W. E. 1975. Orientation of gull chicks exposed
to Project Sanguine's electromagnetic field. Science
189(4197): 143-45.
Spiers,J. M.; Kanitz,J.J. C.; and Novak,J. 1971. Numbers,
speeds, and directions of migrating geese from analysis of
radar display at Fort William, Ontario. Canad. Wildl. Serv.
Rep. Ser. No. 14:69-76.
Stout, G. D.; Matthiessen, P.; Clem, R. V.; and Palmer, R. S.
1967. The Shorebirds of North America. New York:Viking
Press.
Sutter, E. 1957a. Radar als Hilfsmittel der Vogelzugsfor-
schung. Om. Beob. 54:70-96.
Sutter, E. 1957b. Radar-Beobachtungen uber den Verlauf
des nachtlichen Vogelzuges. Rev. Suisse Zoo/. 64:294-
303.
Swinebroad,J. 1964. The radarviewofbird migration. The
Living Bird. 3:65-74.
Thomson, A. L. 1926. Problems of Bird Migration.
London:Witherby.
Tinbergen, L. 1949. Vogels onderweg. Amsterdan: Schel-
tema & Holkema N. V.
49
Sidney A. Gauthreaux, Jr.
Tolle, D. A., and Gauthreaux, S. A., Jr. (in prep.) A radar
and ceilometer study of nocturnal passerine migration in
north central Ohio.
Tucker, V. A. 1975. Flight energetics. In Avian Physiology,
M. Peaker, ed., pp. 49-63. London:Academic Press.
Weir, R. D. 1977. Annotated Bibliography of Bird Kills at
Man-Made Obstacles: A Review of the State oft heArt and
Solutions. Dept. Fish Env., Env. Manag. Serv., Canad.
Wildl. Serv. 85 pp.
Wetmore, A. 1926. The Migration of Birds. Cambridge,
Massachusetts:Harvard Univ. Press.
Weydemeyer, W. 1973. The spring migration pattern at
Fortine, Montana. Condor 75 (4):400-13.
Williams, T. C.;Williams,J. M.;Teai,J. M.; andKanwisher,
J. W. 1972. Tracking radar studies of bird migration. In
Symp. Animal Orientation and Navigation, ·wallops Is-
land, Virginia, pp. 115-28.
Williams, T. C.; Williams, J. M.; Ireland, L. C.; and Teal, J.
M. 1977. Autumnal bird migration over the western North
Atlantic Ocean. Amer. Birds 31 (3):251-67.
Willson, M. F. 1976. The breeding distribution of North
American migrant birds: A critique of MacArthur (1959).
Wilson Bull. 88(4):582-87.
50
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Transmission Line
Wire Strikes:
Mitigation Through
Engineering Design
and Habitat
Modification
Larry S. Thompson
Montana Department of Natural
Resources and Conservation
INTRODUCTION
Collisions of birds with overhead utility wires are
nothing new. Over a century ago, Coues ( 1876) docu-
mented bird kills resulting from collisions with overhead
telegraph lines, and wire strikes have probably been a
continuing source of avian mortality ever since. Wire
strikes have not received a great deal of public or scientific
attention, however, until the last few years as more and
more overhead utility lines are built, heavy bird losses are
reported with increasing ·frequency, and public concern
over future losses becomes great. Unfortunately, much of
the existing problem stems from the fact that nearly all
utility lines operating today were built without knowledge
of the causes, magnitude, or importance of wire strikes-
and, hence, without considering wire strikes in siting or
line design. Thus, we are suddenly realizing that the thou-
sands of miles of overhead wires strung across the conti-
nent -many crossing wildlife refuges and other areas
heavily used by migratory birds -may pose a very real
threat to migratory bird populations, and we must trytodo
51
Larry S. Thompson
something about it. Also, the probability of wire strikes is
acknowledged to be an important consideration in the
environmentally sound design and siting of new line.l3. We
are therefore faced with the dual problem of doctoring
existing lines in an effort to correct past mistakes and of
ensuring that new lines will result in the least possible
collision mortality.
In this paper, I will summarize factors influencing the
probability of wire strikes and discuss means whereby
such losses can be mitigated or prevented. While the small
body of literature developing on wire strikes provides
invaluable information relevant to the mitigation of wire
strike mortality, most of the material presented here is
based upon unpublished data and on conversations with
many knowledgeable individuals. I will also discuss the
significance of wire strikes and the relative cost effective-
ness of efforts toward mitigation.
FACTORS INFLUENCING THE PROBABILITY OF
WIRE STRIKES
Predictability, or the a priori estimation of the prob-
ability of wire strikes under certain conditions, is a
requisite to mitigation. However, there is a dearth of
quantitative information in the literature on specific
circumstances or rates of collision mortality, information
which is essential to predicting high-risk situations.
In certain circumstances, overhead wires may cause a
small but regular loss of birds, which can be measured
over time to estimate rate of kill. This has been attempted
by Willard et al. (1977) who derived estimates of rates of
wire strikes in the Klamath Basin of Oregon ranging from
0.4 to 162 birds per mile per year. Anderson (1978) esti-
mated that from 0.2 percent to 0.4 percent of the maxi-
mum number of waterfowl present were killed by twin
345-kv transmission lines crossing a slag pit in Illinois. By
observing diurnal waterfowl flights in this area, Anderson
found that 0.01 percent of the total flights observed in the
vicinity of the lines (only 4 percent of all flights in the area)
resulted in fatal collisions. Similar results were reported
by Lee (1978), who found 0.03 percent to 0.05 percent of
the estimated total number of flights near the lines
52
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Mitigation Through Engineering and Habitat Modification
resulted in collision mortality during periods of good visi-
bility.
Nevertheless, the most dramatic bird kills caused by
colrisions with overhead wires are often catastrophic,
irregular in time, and hence unpredictable. Agivenstretch
of line may result in negligible bird mortality for many
years, then suddenly-during the chance juxtaposition of
a certain flock of birds with certain adverse weather condi-
tions and a certain disturbance-cause dramatic kills of
hundreds of birds overnight. Thus, it may be argued that
specific mortality rates cannot be quantified, except after
many decades of exhaustive study.
While many questions remain unanswered, sufficient
information exists to draw the following qualitative con-
clusions regarding factors influencing the probability of
wire strikes. This information will serve to guidr. our
efforts toward mitigation until more quantitative data
becomes available.
Species of Bird
Over 80 species of birds, representing 13 orders, have
been documented as victims of wire strikes or electro-
cutions in the United States (Table 1 ). Although this table
represents only a small sample of total mortality, it serves
to illustrate the wide variety of guilds, sizes, and be-
haviors of birds-from hummingbirds to swans-which
are vulnerable to this source of mortality. Scott et al.
(1972) reported 74 specieskilled by powerlines in England
(represented among these species is one order-Cuculi-
formes-not reported in Table 1.)
Estimates of relative or absolute numbers of birds of
various species killed by wire strikes are subject to serious
limitations. First, most published. accounts of dead birds
may be biased toward larger or light-colored birds, which
are more conspicuous, and may also overestimate rates of
losses, as only unusually heavy kills are discovered and
published. Second, reported losses may be only the tip of
this iceberg, as only a very small percentage ofthe total kill
is actually reported; most casualties are either destroyed
by predators, hidden or swept away by water, or left to
decompose along some remote marsh far from the eye of
the biologist.
53
01
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Table 1. Bird Species for Which Mortality due to Overhead Utility Wires has been Documented in the United States.
Order, Species, and Source of Data
PODICIPEDI FORMES (Grebes)
Horned grebe (L. S. Thompson unpubl., J. R. Waters unpubl.)
Eared grebe (D. C. McGiauchlin pers. comm., McKenna and Allard 1976)
Western grebe (D. C. McG!auchlin pers. comm., McKenna and Allard 1976)
Pied-billed grebe (Anderson pers. comm., Krapu 1974 pers. comm., D. C. McGiauchlin
pers. comm., McKenna and Allard 1976)
PELECANIFORMES (Pelicans)
White pelican (G. L. Krapu pers. comm., D. C. McGiauchlin pers. comm., McKenna and
Allard 1976, Peterson and Glass 1946, J. R. Waters unpubl., Willard et al. 1977)
Brown pelican (Willard 1977)
Double-crested cormorant (D. C. McGiauchlin pers. comm., McKenna and Allard 1976,
von Bloeker 1927, J. R. Waters unpubl.)
CICONII FORMES (Herons)
c-:J
Great blue heron (Lee 1977, 1978; Lano 1927; Willard 1977)
Black-crowned night heron (J. R. Waters unpubl.)
Heron spp. (Boeker 1972)
Cattle egret (J. Weise pers. comm.)
Egret spp. (Boeker 1972)
Wood stork (D. Tiller fide G. Grant)
Least bittern (Guillory 1973)
r-1 r1 r:::J r.c:J r:J r-l r--n C-:-J c:--l
Indicated
Cause of
Mortality 1
s
s
s
s
s
s
s
E,S
s
E
s
E
s
s
r----"l c-J l .J
Type of
Wires
Involved 2
p
p
p
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u
P,T
D,P
u
u
u
u
u
F
lJ r-J
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01
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ANSERIFORMES (Waterfowl)
Whistling swan (Willard et al. 1977)
Trumpeter swan (Banko 1960, H. H. Burgess pers. comm.)
Mute swan (D. Willard pers. comm.)
Canada goose (H. H. Burgess pers. comm., McKenna and Allard 1976, Willard et al. 1977)
White-fronted goose (H. H. Burgess pers. comm., Willard et al. 1977)
Snow goose (incl. blue goose) (Anderson 1978, Btockpoet and Hatch 1976, H. H. Burgess
pers. comm., G. L. Krapu pers. comm., Peterson and Glass 1946, Stout and Corn-
well 1976, Willard et al. 1977)
Mallard (Anderson 1978; Krapu 1974; Lee 1977, 1978; D. C. McGiauchtin pers. comm.;
McKenna and Allard 1976; Siegfried 1972; Stout and Cornwell 1976; Willard
etal.1977)
Bufflehead (Lee 1978)
Black duck (Anderson 1978)
Gadwall (Anderson 1978, Krapu 1974)
Pintail (Anderson 1978; Cornwell1968; Griffith 1977; Krapu 1974; Lee 1977, 1978;
McKenna and Allard 1976; Siegfried 1972; Stout and Cornwell 1976; Willard
et al. 1.977)
Green-winged teal (Anderson 1978; Coues 1876; Lee 1977, 1978; D. C. McGiauchlin
pers. comm.)
Blue-winged teat (Anderson 1978, Cornwell and Hochbaum 1971, Krapu 1974, D. C.
McGiauchtin pers. comm., McKenna and Allard 1976, Siegfried 1972, Stout
and Cornwell 1976, J. R. Waters unpubl.)
American wigeon (Anderson 1978, Willard et al. 1977)
Northern shoveler (Anderson 1978, D. C. McGiauchlin pers. comm., McKenna and
Allard 1976)
Wood duck (Anderson 1978, Stout and Cornwell 1976)
Redhead (H. H. Burgess pers. comm., D. C. McGiauchtin pers. comm., McKenna
and Allard 1976)
Ring-necked duck (Boyd 1961 )
~J
s
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s
s
s
s
s
s
s
s
s
s
s
s
s
s
s
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Table 1. Bird Species for Which Mortality due to Overhead Utility Wires has been Documented in the United States. (continued)
Order, Species, and Source of Data
ANSERIFORMES (Waterfowl) (continued)
Canvasback (McKenna and Allard 1976, Willard et al. 1977)
Lesser scaup (Anderson 1978, Krapu 1974, D. C. McGiauchlin pers. comm., McKenna
and Allard 1976, J. R. Waters unpubl., Willard et al. 1977)
Ruddy duck (Krapu 1974; Lee 1977, 1978; D. C. McGiauchlin pers. comm.; Siegfried
1972; Stout and Cornwell 1976; J .. R. Waters unpubl.; Willard et al. 1977)
Fulvous tree duck (McCartney 1963)
Common merganser (Willard et al. 1977)
Merganser spp. {Stout and Cornwell 1976, J. R. Waters unpubl.)
FALCONI FORMES (Hawks and Falcons)
Red-tailed hawk (Boeker and Nickerson 1975, Crawford and Dunkeson 1973,
USF&WS unpubl.)
Rough-legged hawk (USF&WS unpubl.)
Golden eagle (Baglien 1975, Boeker 1972, Boeker and Nickerson 1975, Crawford
and Dunkeson 1973, Hannum et al. 1974, Richardson n.d., USF&WS unpubl.)
Bald eagle (Boeker 1972, Boeker and Nickerson 1975, Crawford and Dunkeson 1973,
Sprunt et al. 1973, USF&WS unpubl.)
Marsh hawk (J. R. Waters unpubl.)
American kestrel (USF&WS unpubl.)
GALLIFORMES ( Gallinacet. .. s Birds)
Greater prairie chicken (Krapu 1976)
Sage grouse (Borell 1939, Myers 1977)
c-J r-l r:-l r=J ~ ~ r:--:""l rl:l r-J ::--l
Indicated
Cause of
Mortality 1
s
s
s
s
s
s
E
E
E
E
?
?
s
s
rl ~
Type of
Wires
Involved 2
p
P,T
D,P
u
p
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D
D
D
D
T
P,T
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:::: "' ~
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:::l
r--
rJ c::-:J r-n r-:J rrT:J CJ [:-=] r-J ~ ~ c--J l"l 1-,-J c-1 LJ [--;-
Ring-necked pheasant (Krapu 1974, D. C. McGiauchlin pers. comm.) s p
Gray partridge (Krapu 1974) s T
Turkey (Boeker 1972) E D
GRUIFORMES (Cranes and Allies)
Whooping crane (J. Reed pers. comm.) s
Sandhill crane (Walkinshaw 1956) s D
Sora (D. C. McGiauchlin, pers. comm.) s u
Virginia rail (D. Kiel and F. Cassel unpubl.) s p
Black rail (Emerson 1904) s -~
American coot (Anderson 1978; Krapu 1974; Lee 1977, 1978; D. C. McGiauchlin .... ~-
pers. comm.; McKenna and Allard 197~; L. S. Thompson unpubl.; Siegfried g.
1972; J. R. Waters unpubl.; Willard et al. 1977) s P,T :::)
;!
CHARADRII FORMES (Shorebirds and Gulls) a
Killdeer (Lee 1977, 1978) s p ~ :::!-
American golden plover (Krapu 1974) s T ~
Common snipe (Lee 1977, 1978; D. C. McGiauchlin pers. comm.) s p '!:! :::)'
Solitary sandpiper (Krapu 1974) s T m ....
Least sandpiper (Emerson 1904, Willard et al. 1977) s T ~-
Western sandpiper (Emerson 1904; Lee 1977, 1978) s P,T Ill
:::)
Buff-breasted sandpiper (Krapu 1974) s T 0..
Marbled godwit (Krapu 1974) s p ~ o-
American avocet (McKenna and Allard 1976) s p -· 6l'
Northern phalarope (Emerson 1904, Willard et al. 1977)
.... s T ~ Glaucous-winged gull (Lee 1977, 1978) s p 9:
California gull (Krapu 1974) s D ~
Ring-billed gull (McKenna and Allard 1976, J. R. Waters unpubl., Willard et al. 1977) s p Ill
01 g.
"""'
Laughing gull (Willard 1977) s -:::)
(11 co
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Table 1. Bird Species for Which Mortality due to Overhead Utility Wires has been Documented in the United States. (continued)
Order, Species, and Source of Data
CHARADRII FORMES (Shorebirds and Gulls) (continued)
Franklin's gull (D. Kiel and F. Cassel unpubl., Krapu 1974, D. C. McGiauchlin pers. comm.,
J. R. Waters unpubl.)
Common tern (McKenna and Allard 1976)
Black tern (D. C. McGiauchlin pers. comm., J. R. Waters unpubl.)
Woodcock (Bailey 1929)
COLUMBIFORMES (Doves)
Rock dove (l. S. Thompson unpubl.)
Mourning dove (Lee 1977, 1978; D. Kiel and F. Cassel unpubl.; Stahlecker 1975)
STRIGIFORMES (Owls)
Great horned owl (Boeker and Nickerson 1975, Edeburn 1973, Emerson 1904,
Fitzner 1975, McCarthy 1973, USF&WS unpubl.)
Short-eared owl (Fitzner 1975, L. S. Thompson unpubl., Willard et al. 1977)
Great grey owl (Nero 1974)
APODI FORMES (Swifts and Hummingbirds)
Allen's hummingbird (Hendrickson 1949)
PIC I FORMES (Woodpeckers)
Yellow-bellied sapsucker (Weston 1966)
r----1 rJ r:LJ r:::J CLJ r=J r-J r:-1 CJ c:--1
Indicated
Cause of
Mortality 1
s
s
s
s
s
s
E,S
s
s
s
s
r-=l ·~
Type of
Wires
Involved 2
P,T
p
D
p
D,F
D,F
F
D
u
lJ c--J
r-
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:::::
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01
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PASSERIFORMES (Perching Birds)
Horned lark (Coues 1876, D. Kiel and F. Cassel unpubl., Stahlecker 1975,
L. S. Thompson unpubl.)
American robin (Lee 1978)
Starling (Lee 1978)
Vireo sparrow (Anderson pers. comm.)
Thrush sparrow (Anderson pers. comm.)
Grosbeak sparrow (Anderson pers. comm.)
Purple martin (Anderson 1933)
Common raven (Boeker 1972)
Common crow (Boeker 1972; Lee 1977, 1978)
Bohemian waxwing (L. S. Thompson unpubl.)
Yellow warbler (D. Kiel and F. Cassel unpubl.)
u.::J
Western meadowlark (Coues 1876, D. Kiel and F. Cassel unpubl., D. C. McGiauchlin
pers. comm.)
Yellow-headed blackbird (L. S. Thompson unpubl.)
Red-winged blackbird (Anderson pers. comm., Lee 1978, McKenna et al. 1976)
Common grackle (D. C. McGiauchlin pers. comm.)
Brown-headed cowbird (D. C. McGiauchlin pers. comm.)
Song sparrow (Lee 1977)
Savannah sparrow (D. Kiel and F. Cassel unpubl.)
Lincoln's sparrow (D. Kiel and F. Cassel unpubl.)
Chestnut-collared longspur (D. Kiel and F. Cassel unpubl.)
McCown's longspur (Coues 1876)
Lapland longspur (Swenk 1922)
1 E =electrocution; S =wire strike;?= uncertain.
LJ l~ [j L_---:J
s F,P,T
s p
s p
s p
s p
s p
E D
E D
E,S D,P
s F
s p
s
s p
s p
s
s
s p
s p
s p
s P,T
s T
s
2 D =distribution line (less than 50 kv); F =fence; P =transmission line (greater than 50 kv); T =telephone or telegraph line;
U = unspecified powerline.
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Larry S. Thompson
It appears, however, thatthe most consistent victims of
wire strikes are large migratory water birds of the orders
Podicipediformes, Pelecaniformes, Ciconi iformes, Anseri-
formes, Gruiformes, and Charadriiformes. Among these,
species whose flocking behavior during migration brings
large numbers of birds together in dense flocks in wet-
lands of relatively small extent are most frequently
reported. Field-feeding puddle ducks are especially
susceptible to collisions with overhead wires due to the
high speed and low altitude of their flights (Boyd 1961,
Krapu 1974, Stout and Cornwell 1976, Willard et al.
1977). Anderson (1978) found blue-winged teal to be
more vulnerable than coots or mallards. Swans, pelicans,
cranes, and "white" geese are also particularly vulner-
ableduetotheirgreatsize, low maneuverability, and flock-
ing behavior (Beer and Ogilvie 1972, Harrison 1963,
Ogilvie 1967, Perrins and Reynolds 1967, Sauey pers.
comm., Walkinshaw 1956, Willard et al. 1977). Scottetal.
(1972) reported that nocturnal migrants appear to be more
susceptible than diurnal migrants. Raptors, due to their
great visual acuity, are rarely the victims of wire strikes but
are vulnerable when distracted or blown off course by
gusts of wind. Whether or not birds of different species are
killed in proportion to their relative abundance has not
been shown.
Condition of Birds
Most authors concur that young, inexperienced birds,
as well as migrants in unfamiliar terrain, appear to be
more vulnerable to wire strikes than resident breeders.
Stout and Cornwell (1976) found negligible sexual differ-
ences in susceptibility of waterfowl. However, Anderson
(1978) found adult mallards to be more vulnerable than
juveniles and male blue-winged teal to be more vulner-
able than females.
Many species appear to be most highly susceptible to
collisions when alarmed, pursued, searching for food
while flying, engaged in courtship, following cones of light
at night, taking off, landing, or when otherwise pre-
occupied and not paying attention to where they are going
(Lee 1977, Willard et al. 1977).
60
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Mitigation Through Engineering and Habitat Modification
Weather and Visibility
Wire strikes appear to be most frequent at night and
during windstorms, snowstorms, periods of heavy fog, or
other meteorological phenomena which reduce visibility
and/ or cause birds to fly lower. Several researchers, how-
ever, have noted both fatal and nonfatal collisions during
periods of clear, calm, daytime weather when visibility is
optimal (Anderson 1978, Krapu pers. comm., Lee 1977,
Walkinshaw 1956, Willard et aL 1977).
Habitat Adjacent to Right-of-Way
Wire strikes of water birds are, of course, most fre-
quent where lines cross water areas or grainfields used by
the birds or where they separate feeding and roosting
areas. Water bird strikes are seldom reported other than in
these situations, but passerines have been found be-
neath lines crossing upland habitats(Cassels pers. comm.,
Stahlecker 1975). Gull concentrations near a sanitary
landfill were reported by Lee ( 1977) to suffer heavy losses.
Willard et aL (1977) suggest that lines within a single
habitat, e.g., a grainfield, are more likely to cause
bird/wire strikes than lines running between different
habitats.
Type of Wires
The physical configuration of lines in space (the strike
zone) is of great importance in determining risks of wire
strikes. It is also perhaps easier to change than the char-
acteristics of birds in attempting to mitigate losses. Wires
of all sorts, including fences, telegraph lines, telephone
lines, power distribution lines, guy wires, and power
transmission lines, have resulted in bird casualties (Table
1 ). The small diameter, low (less than 20 feet), high-
density lines (especially telephone lines, which may have
20 or more small wires strung between structures, and
lower-voltage transmission and distribution lines, which
are often underbuilt at various heights on the same set of
poles) appear to be the major source of wire strikes, but
they are also much more abundant than transmission
lines. There is some evidence that the large conductors of
61
Larry S. Thompson
extra-high voltage lines are more visible than smaller con-
ductors or ground wires, especially when strung in
bundles, and hence result in fewer wirestrikes(Lee 1977,
Willard et al. 1977). These extra-high voltage conductors
may also alert birds to their presence through corona dis-
charge and associated noise or by electromagnetic field
effects, although this has not been demonstrated (Lee
1977). The overhead ground, or static, wire is often impli-
cated as a major culprit in bird losses involving higher volt-
age lines because birds will fly over the more visible con-
ductor bundles only to collide with the relatively invisible,
thin static wire (R. Hamilton pers. comm., R. A. Hunt pers.
comm., R. Johnson pers. comm., D. Loomis pers. comm.,
Scott et al. 1972, Willard et al. 1977).
OPPORTUNITIES FOR MITIGATION
Transmission line siting is often approached initially by
identifying a corridor, often several kilometers wide,
which is broadly suitable for a transmission line. Corridor
selection is followed by centerline selection, or on-the-
ground determination of the precise route of the line,
which in turn is followed by actual engineering and con-
struction of the line. It is essential to consider mitigation at
each of these three stages of the facility siting process, as
described below. Since very few specific mitigating
measures have actually been implemented and studied, I
am unable to present here a definitive, state-of-the-art
report as to relative effectiveness. Instead, I will sum-
marize feasible suggestions and ideas with the hope they
will be pursued in greater depth as a result of this
workshop.
Corridor Selection
The decision where-or whether-to build a new line
may be the most important mitigative tool we have. If it can
be shown that broad geographical areas between pro-
posed endpoints of a new line differ in risk for wire strikes,
mortality can obviously be reduced by staying well away
from areas with a high-risk potential. These areas include
wetlands in general, waterfowl concentration areas, fly-
62
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Mitigation Through Engineering and Habitat Modification
ways, roosting areas, feeding areas, low passes, breeding
areas, and especially the paths used by migrants for
periodic feeding flights. If the area between line end-
points is of uniform impact risk, losses may be mitigated
only by not building the line overhead or by selecting a
feasible engineering alternative with other endpoints.
Corridor selection-depending on the width of the
corridor-provides a very coarse, but nevertheless impor-
tant, means of mitigation. If wetlands or other high-risk
areas can be avoided by distances of several miles, the
probability of catastrophic losses will be greatly reduced.
Unfortunately, moving a corridor to bend around a critical
area increases both the length and the costofthe line. Fig-
ure 1 shows approximate costs per circuit kilometer of
lines of different voltages and indicates costs involved in
deviating from a straight line. Also, wire strikes are not the
only consideration in corridor selection. They may be
treated with low priority when land use, socioeconomic
problems, human populations, and physical
characteristics of the landscape are simultaneously
considered. Thus, even with the best planning, new
corridors may have to include wetlands or other high-risk
areas, and we must look toward other means for
mitigation.
Centerline Selection
Within a corridor several kilometers wide, there are an
infinite number of possible centerline locations, and cen-
terline placement provides the opportunity for a much
finer degree of spatial mitigation than does corridor
selection. In water bird concentration areas, a four-season
study of the corridor by a waterfowl specialist should be
conducted to determine local movement patterns and
optimum line placement. The studies carried out by
Willard eta I. (1977) and proposed by Lee and Meyer(1977)
provide excellent models for such investigations. Local
low-level feeding flights are. of particular concern, and
utilities should be required to obtain information regarding
the size, composition, seasonality, and repetition of such
flights so that flight paths can be avoided wherever
possible.
63
Larry S. Thompson
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Figure 1. Estimated costs of overhead and underground powerline
installation.
Several specific mitigative measures involving center-
line siting may be effective where waterfowl concentra-
tion areas cannot be avoided. Scott et al. (1972) suggest
line placement parallel, rather than perpendicular, to pre-
dominant lines of flight. It is also likely that lines sited adja-
. cent to cliffs, tall buildings, windbreaks, or at the base of
low hills (Figure 2) will result in fewer losses than lines in
flat terrain as birds in flight begin gaining altitude in
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response to these highly visible features and thus fly well
over the lines. Also, clustering lines, or sharing the same
right-of-way with several types of lines, may be prefer-
able because the network of wires is more visible and con-
fined to a smaller area. Birds in flight would have to make
only one climb and descent to cross a cluster of lines,
whereas separate lines would require many such maneu-
vers {Figure 3). However, the hazard to birds during per-
iods of decreased visibili~y may be greater where many
lines are clustered together, forming a virtual obstacle
course to flocks flying at many different heights {Figure 4) .
The relative effect on mortality rates of separate versus
clustered lines depends on many site-specific factors and
deserves careful study.
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65
Larry S. Thompson
A
Figure 3. Mitigation by clustering lines at river crossings. Note that two
climbs and descents are required at A while only one is necessary at B.
Another possibility for mitigation involves judicious
centerline placement in relation to local climate. Avoiding
areas of frequent and heavy fog can reduce the probability
of wire strikes. It may also be possible to locate conductors
parallel, rather than perpendicular, to prevailing winds,
thereby reducing the likelihood birds will be blown per-
pendicularly into wires. Wind roses, as shown in Figure 5,
could provide useful information applicable to centerline
placement, although prevailing wind direction may not be
clear in some areas (Figure 5A) or may differ in the same
area between se-asons (Figures 58 and 5C). In the latter
example, siting the centerline parallel to prevailing spring
winds would result in crosswinds and a greater prob-
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ability of wire strikes in the fall. Wind direction is probably
more important in fall than in spring, since hunting pres-
sure has been shown to increase the nocturnality of duck
movement (Willard et al. 1977). This type of mitigation is
probably most applicable to lines in river canyons where
winds are topographically confined yearlong to a certain
direction (Figure 6).
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B
Figure 4. Separate lines (A) versus clustered lines (B). While the proba-
bility of a flock of birds encountering a line is greater at A, the risk of
collision in a flock of birds passing through the lines during poor
visibility is greater at B.
67
Larry S. Thompson
A
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Area II
Spring Fall
Figure 5. Hypothetical wind roses for two areas, the first (Area I) show-
ing little predominance of wind direction and a second (Area II) show-
ing strong seasonal predominance of direction which differs from
spring to fall. Direction of lines indicate wind direction in each of 16
compass points, and length of lines indicates the percentage of time the
wind blows in that direction.
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canyons, wire strikes can be mitigated by line placement parallel, rather
than perpendicular, to wind direction and by crossing the river ob-
liquely rather than perpendicularly. In this figure, A is preferable to
Bore.
Mitigation by Engineering Design
The following mitigative measures may be applicable
both to designing new lines and to reducing losses on
existing lines which are causing considerable bird
mortality and which cannot feasibly be moved.
Undergrounding. If conductors are buried, the
chances of wire strikes are, of course, reduced to zero. This
is quite feasible for telephone and power distribution lines,
and in certain cases it may actually be cheaper than over-
head construction. However, as voltage rating increases,
cost increases exponentially, and risk for detrimental
impacts to resources other than waterfowl may also in-
crease significantly (see Schiefelbein 1977). Figure 1
compares costs of overhead and underground transmis-
sion for a variety of voltages, based on currently available
technology. Termination costs, or the costs of "going
under" at each end of the underground segment, are con-
sidered separately as these are roughly the same regard-
less of line length. (Total underground costs are cal-
culated from Figure 1 by multiplying the cost per unit
length by total length and adding twice the indicated
termination costs.) Technology has been proven only for
voltages of 69 kv and below; high voltage underground
technology is presently in prototype stage. In fact, out of
5373 miles of 1 00-kv lines projected over the period 1976
69
Larry S. Thompson
to 1981, only 56 miles are planned as underground
(Federal Power Commission, Bull. 22175, February 26,
1976). Less than 1 mile of gas-insulated, prototype, under-
ground, 500-kv transmission line has actually been built
(Ray pers. comm.).
Tower Design. For 500-kv metal-lattice towers, two
basic tower designs are available -guyed and free-
standing (Figure 7). Guyed towers are relatively
lightweight and are used exclusively as suspension
towers, that is, towers which simply hold the wires off the
ground. The guy wires leading from these towers may
pose an additional collision hazard, which can be
mitigated by using self-supporting towers at river
crossings or in wetlands. Self-supporting towers are also
used as suspension structures, but the larger and sturdier
designs may be used as dead-end structures (capable of
withstanding a strong lateral pull, as from unbalanced
conductor tension) as well. Although the range of costs of
self-supporting towers ($24,000 to $72,000) is greater
than that of guyed towers ($18,000 to $23,000), self-
supporting towers are often required in any case at water
crossings, since the long spans involved require greater
tower strength.
Presence of Static Wires. As mentioned above, the
static wire is smaller and hence less visible than conduc-
tors on higher voltage lines, and it appears to be a major
cause of collision mortality. This hazard may be reduced
simply by eliminating the static wire from spans crossing
wetlands. However, there are two major objections. The
purpose of the static wire is to intercept and drain the elec-
trical charge from a lightning strike; if the wire is not
present, the lightning bolt can strike conductors and cause
relays to trip out. Indeed, I ightni ng appears to be the major
single cause of powerline outages in the U. S.
(Schiefelbein 1977). In many areas, charts of lightning
frequency are available, and the probability of lightning
striking a given span may be calculated. Even in areas of
low lightning frequency, though, eliminating the static
wire will slightly increase the probability of lightning-
caused outages. Since eliminating the static wire over a
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certain span causes lateral stress on the towers at the
ends of the span, dead-end structures, at a greatly in-
creased cost, would be required. This increased cost could
be somewhat offset by savings in the price of the static
wire, which has been estimated by Bonneville Power
Administration to exceed $13,000 per mile of single-
circuit 500-kv line (Schiefelbein 1977).
Height of Conductors. One suggested means of miti-
gation is to adjust the height of conductors above ground
to avoid predominant approach flight path heights ofthose
birds using nearby water areas. However, there are
several serious problems with this approach. First, flying
heights and approach patterns of birds vary greatly by
species, season, and weather conditions. Birds which fly
at great heights during clear, calm weather may fly very
close to the ground during periods of poor visibility and
thus be vulnerable to wires of varying height. Also, con-
ductors sag in the middle and may be over twice as high
near the tower as at midspan. Upper and lower bounds are
put on the available range of heights of conductors by the
increasing costs of taller towers and by minimum ground
clearance standards, respectively (Table 2).
Since wire strikes are so often associated with low visi-
bility, some advantage may be gained by installing con-
ductors on the highest towers possible. This may cause
additional problems, though, with species reluctant to fly
under the conductors, thereby increasing their chances of
collision with the static wire, not to mention the problem of
increased cost.
Where lines cross forested lands, tower height can
sometimes be reduced to that of the trees, reducing above-
canopy exposure and thus lowering the risk of collision to
Table 2. Approximate Minimum Ground Clearance for Powerlines of
Different Voltages
Voltage ( kv)
Clearance (ft)
Clearance (m)
72
15 69 115 161 230 500
22 24 25·27 27·29 30-31 35
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Mitigation Through Engineering and Habitat Modification
birds flying over the treetops (Figure 8). This requires
shorter spans and more towers to maintain minimum
ground clearance, and it may be costly. Losses might be
reduced by keeping all lines between towers in roughly the
same horizontal plane, that is, employing a flat conductor
configuration rather than a delta or stacked configura-
tion. This effectively reduces the vertical dimension of the
potential strike zone. To be effective, however, the static
wire must remain above the plane of the conductors.
Increasing Visibility of Wires. Measures which
A. High-Hazard Situation
B. Corrected Situation
Figure 8. In areas where flocks of birds commonly fly just above the
forest canopy, wire strikes can be mitigated by placing the lines just
below the treetops. The horizontal, dotted line indicates minimum
ground clearance of the conductors, and lowering the line while main-
taining this clearance requires more towers and shorter spans.
73
Larry S. Thompson
increase the visibility of wires (especially static wires)
would theoretically decrease the probability of birds' col-
liding with the wires. Daytime wire visibility may be
enhanced by increasing the diameter or by changing the
color or reflectivity of the wire. Collision hazard seems to
be roughly inversely proportional to wire diameter, and
although larger diameter conductors are preferable
electrically, they are also more expensive and require
stronger towers. Stringing conductors in bundles, a
common practice for higher voltage lines, increases ap-
parent conductor diameter and hence visibility. No
information is available on the relative visibility of differ-
ent color wires to birds, although dark wires would
probably be most visible against an overcast sky and
bright, reflective wires would likely be most visible on
sunny days.
Visibility of wires may also be increased by attaching
highly visible objects to them. Large, colored spheres of
the type frequently used on lines near airports or on long,
high spans may be installed at a cost of approximately
$100 each. While birds may very well see these spheres,
they may still fail to see the wires between and may strike
the wires while swerving to miss the spheres. Scott et al.
( 1972) reported that 15-centimeter black tapes tied at 1.9-
meter (6-foot) intervals along static wires have been
effective in reducing bird casualties in England. The same
authors reported an experiment in England in which static
wires were marked at 1.2-meter (4-foot intervals) with 5-
centimeter bands of luminous orange tape, or with lumi-
nous orange strips having a free-hanging tail 5
centimeters long. Casualties were somewhat lower on
marked spans during the 3 years after marking than during
the preceding 3-year period. The number of casualties at
marked spans was also lower than at adjacent unmarked
spans during the 3 years after marking. However, differ-
ences were not significant and were probably overridden
by effects related to line placement. The relative effective-
ness of the two marking techniques could not be deter-
mined, although the orange strips faded to white 18
months after marking. Marking wires with other devices
such as ribbons, streamers, flags, or even plastic wind-
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mills of the type seen in used car lots may be effective in
reducing losses and should be tested in the future. Dis-
advantages of this type of mitigation are the aesthetic
impact of such marking and nighttime ineffectiveness.
Wire visibility may be increased at night by attaching
reflective or luminous objects to the wires or by giving the
wires a reflective or luminous coating and providing a
nighttime light source. The expense and logistical prob-
lems of illuminating long spans of transmission lines
would be formidable, and there is some evidence that
night floodlighting may be countereffective. Several
authors (Avery et al. 1976, Cochran and Graber 1958,
Johnston and Haines 1957, Laskey 1960, Rybak et al.
1973, Weir 1976) found that nocturnally migrating birds
are attracted to the "white hole" created by a bright beam
of light; they become blinded or disoriented, often flying
around within the beam for hours or until exhausted or
killed by striking objects. Avery (pers. comm.) and Weir
(1976) suggest that strobe lights may be much more
effective than floodlights in reducing collision mortality, ·
although in at least one case (Whelan 1976) strobes did
not provide an improvement over continuous light. Some
evidence suggests red strobe lights may be preferable to
white (Weir 1976), but much work is needed to determine
optimum frequency, color, intensity, direction, and loca-
tion relative to the lines. One manufacturer (Flash Tech-
nology of America pers. comm.) has developed a strobe
model (FTB-205 B) specifically for use on transmission
towers. Nighttime illumination of wires has not been ade-
quately tested; it certainly could not be expected to pre-
vent losses due to the preoccupation of startled or flock-
ing birds or to birds being thrown off course by gusts of
wind.
Repelling Birds from the Vicinity of Conductors. The
probability of wire strikes can be reduced if the birds are
somehow kept away from the vicinity of the lines. This may
be accomplished by making habitat near the lines
relatively less attractive than habitatfartherfrom the lines
(as discussed above) or by chasing or scaring birds away
from the lines with some sort of auditory or visual stimu-
lus. Wind-operated whistles or bells have been sug-
75
Larry S. Thompson
gested, but they would probably be of limited effective-
ness. A device known as Av-alarm™, which produces
high-frequency "distress" sounds effective in repelling
certain species of birds, has been used in connection with
TV towers and airport ceilometers with limited success
These devices are rather expensive, of unknown effec-
tiveness in repelling water birds(which may habituate to a
constantly repeated sound), and impractical to install
along long lengths of powerline. Windmills or wind-
animated scarecrows made to resemble hunters, canids,
or raptors may be effective in repelling birds during day-
light hours. Raptor silhouettes cut from paper have
reduced avian collisions with a glassed-in walkway in
Pullman, Washington (Johnson and Hudson 1976), and
owl dummies have reduced the number of pigeons
roosting on an interstate highway bridge just east of
Seattle, but similar devices to repel waterfowl have not
been tested. Encouragement of raptor nesting on towers
as a waterfowl deterrant merits study.
A problem with this type of mitigation is that otherwise
attractive habitat is rendered unavailable to a segment of
the bird population, .forcing it into less suitable habitat
elsewhere. This may have an effect on carrying capacity as
great, or greater than, wire strike mortality and may render
this type of mitigation counterproductive. Again no data is
available to document this supposition.
Shielding Structures. If wires can be screened by
trees, billboards, or other man-made structures, it is quite
likely collisions can be reduced or prevented. Many bird
species are ·reluctant to fly under objects, and ducks in
particular begin gaining altitude well ahead of an obstacle
in their path (Fog 1970, Gunter 1956). Shelterbelts,
bridges, billboards, high wooden fences, walls, or other
highly visible structures can force birds to fly over lines
even if they cannot see the wires (Figure 9). These flight
path barriers could probably be effective even if much
lower in height than conductors or if some distance from
the right-of-way, provided they are located optimally a long
the flight path of the birds. Further study oft he behavior of
birds in relation to obstacles in their flight path would
allow optimum placement of such barriers. Of course,
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Mitigation Through Engineering and Habitat Modification
such structures would havetobedesignedtopreventbirds
from colliding with them, and they have the potential of
being eyesores. This type of mitigation would probably be
most effective for smaller lines (especially telephone and
distribution) or at multiple-line river crossings.
Preventing Distraction of Birds_. It has been noted that
birds are highly vulnerable to collisions when startled or
distracted. Pr"ohibiting hunting or travel (perhaps by
closing access roads parallel to lines through wetlands)
may serve to reduce collision losses.
A. High-Hazard Situation
B. Corrected Situation
Figure 9. Mitigation by placing highly visible structures next to the line
to alter flying height of birds.
77
Larry S .. Thompson
Mitigation by Habitat Modification
If the habitat factors which make certain powerline
rights-of-way attractive to birds are known, the opp·or-
tunity exists to mitigate wire strikes by making certain
habitats relatwely less suitable or attractive to high-risk
species. I emphasize relatively since it may not be desir-
able to degrade right-of-way habitat quality, and hence
carrying capacity, simply to lower mortality rates-no one
is going to recommend draining or filling a wetland
crossed by a powerline simply to lower the incidence of
collision mortality. Perhaps a better approach would be to
make nearby habitat more attractive, thereby not only
attracting birds away from a high-risk situation but
benefiting the population as well. This means may be par-
ticularly effective with respect to feeding flights; in cases
where feeding and roosting areas are separated by a
powerline, it may be advantageous to create new feeding
and resting areas, as shown in Figure 10. Lee (1977)
mentioned large kills of gulls flying between a wetland and
a sanitary landfill; changing the location of the landfill
could reduce these losses. Although these measures may
be expensive, they may very well be less expensive and
more beneficial than some of the contrived engineering
solutions noted above. They will certainly not be applic-
able, however, in all situations.
A corollary measure involves changes in local land use
patterns on and near the right-of-way in order to change
local flight patterns of migratory birds. For example,
reversing the locations of a grainfield used as a feeding
area and an alfalfa field (Figure 11) may reduce collision
mortality. Willard et al. (1977) found that grainfields in the
Klamath Basin of Oregon were more attractive to
waterfowl than pastures, especially just before or just
after harvest, and that plowing greatly reduced ·
attractiveness while flooding increased it. It is thus
possible to remove or relocate the feeding enticement by
changing the timing or location of flood irrigation.
Experience has shown that landowners are often
reluctant to make such dramatic changes voluntarily, and
it would pose considerable problems to force them to do so
outside the right-of-way. Consequently, these habitat
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A. High-Hazard Situation
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B. Corrected Situation
Figure 10. In some cases, local feeding flight patterns may be changed
by creating new feeding and/or resting areas.
changes may be most practical on public land or along
multiple corridors. Also, traditional flight patterns may be
difficult to change through habitat modification.
79
Larry S. Thompson
A. High-Hazard Situation
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Figure 11. Mitigation by local land use change. Reversing the locations
of attractive and unattractive land uses in the vicinity of a powerline
may change waterfowl feeding flight patterns.
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DISCUSSION
Significance of Wire Strikes
The "significance" of an adverse impact to wildlife
really incorporates two distinct concepts -biological
significance and social acceptability (Buffington 1976). A
biologically significant impact is one which is long-term
and which results in a measurable change in carrying
capacity or ultimate population size. In this respect, the
impact of wire strike mortality on bird populations can be
judged biologically significant only if it exceeds the
compensatory response capability of the population and
thus results in a measurable population decline. That this
is the case with any waterfowl species is highly doubtful,
since waterfowl populations are able to compensate for
substantial hunting mortality, which is much greater than
collision mortality (Anderson and Burnham 1976). Stout
and Cornwell ( 1976) estimate that wire strikes comprise
about 0.1 percent of total waterfowl non hunting mortality
in their sample; hunting mortality, in comparison, prob-
ably affects 20 percent to 30 percent of waterfowl popula-
tions (Anderson and Burnham 1976, McGregor pers.-
comm., Willard et al. 1977). Losses of certain rare species
with lower compensatory ability may indeed be biologi-
cally significant -loss of five whooping cranes to wire
strikes could be disastrous to the population. The extent of
our knowledge today is such that we may not be able to
perceive or measure changes in carrying capacity attribut-
able to wire strikes, even if they are sizable and long-term.
Should wire strikes be found not to significantly affect
population size over the long-term, they may be important
in another respect, namely, social acceptability. The public
sensitivity may be so affronted by the loss of 10 whistling
swans that this loss constitutes a very real social impact
and is deemed by society to be unacceptable, although the
loss may not be biologically significant. The recent public
outcry over the proposed Midpoint to Medford 500-kv lines
(which would cross Oregon's Klamath Basin, a very
important waterfowl concentration area) illustrates this
point well: The public simply does not want to see birds
killed by powerlines, regardless of the biological signifi-
cance of such losses.
81
Larry S. Thompson
The concern has also been raised that, while losses
may not affect ultimate population size, they may be
_reducing the harvestable surplus of waterfowl available to
hunters. The assumption that nonhunting mortality is
largely replaced by hunting mortality may not be true
above certain threshold values (Anderson and Burnham
1976, Stout and Cornwell1976), and post-hunting season
mortality may have an important effect on populations.
Cornwell (1968) believed that wire strike losses add to,
rather than replace, hunting mortality.
It maybe relevantatthispointtobring up the concept of
maximum sustainable yield (see Sharma [1976] for a
discussion of this concept in relation to impact signifi-
cance). If we assume that a fixed proportion of the popula-
tion of migratory birds can and will be lost to various types
of mortality (predation, disease, starvation, shooting, wire
strikes, etc.) each year without affecting carrying capacity
-that is, the maximum sustainable yield -we may
allocate certain portions of this harvestable surplus to the
various sources of mortality (Figure 12) and manage
accordingly.
Society may deem wire strike mortality to be an unfor-
tunate but unavoidable phenomenon and thus allocate a
certain percentage of the harvestable surplus to these
losses rather than acceptthe costs of mitigation. This non-
action amounts to saying that a certain amount of wire
strike mortality is part of the cost society must pay for a
convenient source of energy. If carrying capacity is to
remain constant, the magnitude of other types of mor-
tality will have to adjust downward. This includes hunting
mortality, and the social impact of reduced availability of
waterfowl to hunters hardly needs mention.
On the other hand, wire strike losses may be judged
unacceptable, and society must then attempt to channel
money, energy, and resources into efforts to mitigate or
prevent losses. Society is then faced with the problem of
optimizing the balance between various social costs of
mitigation and the benefits of reduced wire strike
mortality.
82
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Mitigation Through Engineering and Habitat Modification
Other Man-Caused
Mortality (Future)
Reserve
Margin
Hunter Harvest
Natural Mortality
Figure 12. The maximum sustainable annual mortality of populations
can, to some extent, be differentially allocated to specific types of mor-
tality without affecting carrying capacity or long-term population size.
(Modified from Sharma 1976.)
Costs Versus Benefits of Mitigation
A couple of hypothetical examples may best serve to
illustrate the difficulty of balancing the costs and benefits
of mitigation. Let us assume we could accurately predict
the rate of wire strike mortality of a proposed twin 500-kv
transmission line through the center of a circular wetland
10 kilometers in diameter to be 100 kilograms of
waterfowl per circuit-kilometer per year. In order to skirt
this wetland completely, each line would have to be
increased in length by C0"/2-10) kilometers, or 5.7
kilometers. The increased cost of doing so, assuming a
cost of -$125,000 per circuit-kilometer, would be
$1,425,000. This compares with 80,000 kilograms of
83
Larry S. Thompson
waterfowl that would be "saved" assuming a 40-year life
of the line (1 00 kiloQrams per circuit-kilometer per year
times 2 circuits times 10 kilometers times 40years). Thus,
the cost to society per kilogram of waterfowl would
be $17.81. This may be unreasonably expensive,
especially since the losses may not be biologically
significant and the "lost" kilograms of waterfowl are never
actually recovered.
For another exc;~mple, let us consider a pond 0.1
kilometer wide which will be spanned by a 500-kv line
using 23-meter guyed structures on each side. Using the
same hypothetical rates of wire strikes noted above,
approximately 400 kilograms of waterfowl would be lost
over the 40-year life of the line. Assuming these losses
could be prevented by eliminating the static wire, thus re-
quiring self-supporting towers which are (by best 1977
estimates) approximately $1 00,000 more expensive to
install, society is, in effect, paying $250 per kilogram of
waterfowl. If losses could be prevented by installing
colored flags on the guy wires at a cost of $1 ,000, the cost
to society could be reduced to $2.50per kilogram of water-
fowl.
These may be artificial examples, but they serve to
illustrate an important point: Costs of mitigation must be
weighed carefully against the benefits to be obtained. This
problem would be sufficiently difficult to solve under any
circumstances, but it is compounded by the fact that wild-
life values (despite several recent attempts) are essenti-
ally unquantifiable. How much is a duck worth? a cormo-
rant? a whooping crane? The U.S. recently settled a
Canadian claim for ducks killed by an oil spill by paying the
Canadian government $2 per duck (Efford 1976), and the
possibility exists that utilities may be required to reim-
burse the public a dollar value for waterfowl losses
attributable to wire strikes. But what is the monetary value
of a lost opportunity for a hunting experience? In another
recent case, the court awarded a wetland owner $90,000
damages for alleged avoidance by birds of his land be-
cause of nearby powerlines (Bonde 1970).
Obviously, whatever the value of waterfowl, the point
0 is ultimately reached where further investments in
84
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Mitigation Through Engineering and Habitat Modification
mitigating measures yield diminishing returns in terms of
waterfowl abundance. Long before this point is reached,
serious consideration should be given to compensation of
wire strike losses as an alternative to mitigation.
Compensation of an Alternative to Mitigation
In the example of the twin 500-kv lines through a
circular wetland, $1,425,000 was the cost estimate of
mitigation through centerline placement, and the benefits
to be obtained amounted to 2,000 kilograms of waterfowl
saved annually. If the line were built as originally planned,
through the center of the marsh, the money is saved while
the ducks are lost. What benefits could be obtained by
using this same amount of money instead for waterfowl
habitat improvement, wetland acquisition, winter feed-
ing, law enforcement, or other long-term increases in
carrying capacity? It is likely they could far exceed the
benefits to be obtained by merely preventing a relatively
small percentage of nonhunting mortality.
While compensation is an attractive alternative to
mitigation, it is not the final answer, especially where
"out-of-kind" compensation is involved. No amount of
mallard habitat improvement can compensate for the loss
of a flock of whooping cranes to wire strikes. Serious
logistical difficulties may be encountered by efforts to
compensate snow geese losses in the U.S. by improving
breeding habitat in Canada, although Pacific Power and
Light is considering a proposal by Ducks Unlimited to com-
pensate for collision losses in Oregon by contributing
$248,000 to habitat acquisition in Canada. Probl.ems in
forcing utilities to make such compensation would be
formidable. Nevertheless, it is an alternative which, in
some cases, would yield greater benefits than mitigation
and should be considered on a case-by-case basis.
The point is not that mitigation is unimportant. The
point here is simply that creating additional h.abitat may, in
some cases, be a better use of available money than
developing more and more sophisticated and energy-
intensive "technological fixes" such as strings of lights or
electronic noisemakers.
85
Larry S. Thompson
SUMMARY AND CONCLUSIONS
Transmission line wire strikes by migratory birds are an
increasingly serious problem in the United States. While a
great many species are affected, large water birds are the
most consistent victims, and losses are heaviest in water-
fowl concentration areas during periods of wind, fog, rain,
or nighttime feeding activity. Initial siting of lines away
from hazard areas is perhaps the most direct approach to
mitigation but cannot always be implemented because of
other siting constraints. Where lines cross high-risk areas,
losses may be reduced by a variety of means, including
underground installation, changes in tower design, re-
moval of static wires, changes in conductor height,
increasing wire visibility, repelling birds from the vicinity
of conductors, installing shielding structures, preventing
distraction of birds, and local habitat modification. Most of
these mitigating measures have not been tested, but the
most promising short-term solutions appear atthis time to
be the following: marking wires (especially static wires
and guy wires) with permanent, highly visible flags or
strips; changing flight patterns of birds by installing highly
visible banners parallel to the lines or by altering land use
patterns adjacent to the right-of-way; and clustering lines
at river crossings. The biological significance of wire
strikes may not be great, but the public relations value to
utilities of attempting mitigation can be high. The costs of
many potentially effective mitigating measures outweigh
the benefits to be obtained, and in some cases
compensation by habitat improvement may be preferable
to mitigation. Priorities for future research should be the
evaluation of rates, causes, circumstances and popula-
tional significance of wire strikes on different types of lines
(with particular reference to the importance of the static
wire); development of wire markers, warning devices, or
alternative tower designs which are effective but not pro-
hibitively expensive; and exploration of them any untested
mitigative measures discussed above.
86
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ACKNOWLEDGMENTS
I extend mysincerethankstothe many individuals who
took time to discuss this topic with me and whose ideas
form the bulk of this paper. Much of the material pre-
sented here was gathered during the course of transmis-
sion line impact evaluations carried out by the Energy
Planning Division, State of Montana.
REFERENCES
Anderson, A. H. 1933. Electrocution of purple martins.
Condor 35:204.
Anderson, D. R., and Burnham, K. P. 1976. Population
Ecology of the Mallard. VI. The effect of exploitation on
survival. U.S.D.I. Fish and Wildlife Service Resource Publi-
cation 128.
Anderson, W. L. 1978. Waterfowl collisions with power
lines at a coal-fired power plant. Wildlife Society Bull. In
press.
Avery, M.; Springer, P. F.; and Cassel, J. F. 1976. The ef-
fects of a tall tower on nocturnal bird migration-a port-
able ceilometer study. Auk 93:281-91.
Baglien, J. W. 1975. "Biology and habitat requirements
of the nesting golden eagle in southwestern Montana."
M.S. Thesis, Bozeman: Montana State University.
Bailey, A.M. 1929. Bird casualties. Wilson Bull. 41 :106-7.
Banko, W. E. 1960. The trumpeter swan: its history, habits
and population in the United States. North American
Fauna. No. 63. April 1960.
Beer, J. V., and Ogilvie, M. A. 1972. "Mortality." pp.
125-42 in Peter Scott and the Wildfowl Trust, The Swans.
Boston: Houghton Mifflin Co.
Blockpoel, H., and Hatch, D. R. M. 1976. Snow geese, dis-
turbed by aircraft, crash into power lines. Canad. Field-
Nat. 90:195.
87
Larry S. Thompson
Boeker, Erwin L. 1972. Powerlines and Bird Electrocu-
tion. U.S. Bureau of Sport Fisheries and Wildlife, Forest
Hydrology Lab. Tempe: Arizona State University.
Boeker, E. L., and Nickerson, P. R.1975. Raptorelectrocu-
tions. Wildlife Society Bull. 3:79-81.
Bonde, Loren J. 1970. U. S. Game Management Agent,
U.S.D.I., Bureau of Sport Fisheries and Wildlife. Letter to
Richard A. Hunt, October 5, 1970.
Borell, A. E. 1939. Telephone wires fatal to sage grouse.
Condor 41 (2):89.
Boyd, H. 1961. Reported casualties to ringed ducks in the
spring and summer. Wildfowl Trust 12:144-46.
Buffington, J.D. 1976. A synthetic definition of biological
significance. In Proceedings of the Conference on the
Biological Significance of Environmental Impacts. eds. R.
K. Sharma et al., pp. 319-27. Washington, D. C.: U.S. Nu-
clear Regulatory Committee.
Cochran, W. W., and Graber, R. R. 1958. Attraction of noc-
turnal migrants by lights on a television tower. Wilson
Bull. 70:378-80.
Cornwell, G. W. 1968. Needless duck deaths. Conserva-
tion Catalyst 2:15-18.
Cornwell, G. A., and Hochbaum, H. A. 1971. Collisions
with wires-a source of anatid mortality. Wilson Bull.
83:305-6.
Coues, E. 1876. Destruction of birds by telegraph wire.
Amer. Nat. 10:734-36.
Crawford, J. E., and Dunkeson, L. A. 1973. Powerline
standards to reduce raptor losses on the national re-
source lands. Draft report. Bureau of Land Management
and Bureau of Sport Fisheries & Wildlife.
Edeburn, R. M. 1973. Great horned owl impaled on barbed
wire. Wilson Bull. 85:478.
88
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Mitigation Through Engineering and Habitat Modification
Efford, I. E. 1976. Problems associated with environmen-
tal impact studies in Canada. In Proceedings of the Con-
ference on the Biological Significance of Environmental
Impacts. eds. R. H. Sharma et al. pp. 25-42. Washington,
D. C.: U. S. Nuclear Regulatory Committee.
Emerson, W. 0. 1904. Destruction of birds by wires.
Condor. 6:37-38.
Fitzner, R. E. 1975. Raptor mortality on fences and utility
lines. Raptor Res. 95:55-57.
Fog, J. 1970. Effectofhighvoltageelectricallinesonflying
height of Anatidae. Flora. Fauna. Silkeborg 76:141-44.
(Engl. summl.)
Griffith, D. B. 1977. Selected biological parameters asso-
ciated with a :!:400-KV d-e transmission line in Oregon.
Bonneville Power Administration, Portland, Oregon.
Guillory, H. D. 1973. Motor vehicles and barbed wire
fences as major mortality factors for the Least Bitterns in
southwestern Louisiana. IBBA News 45:176-77.
Gunter, G. 1956. On the reluctance of gulls to fly under
objects. Auk 73:131-32.
Hannum, G.; Anderson, Wayne; and Nelson, M. 1974.
Powerlines and birds of prey. Report presented at North-
west Electric Light and Power Association, 22 April1974,
Yakima, Washington.
Harrison, J. 1963. Heavy mortality of mute swans from
electrocution. Ann. Rep. the Waterfowl Trust 1961-62.
14:164-65.
Hendrickson, J. R. 1949. A hummingbird casualty.
Condor 51 :1 03.
Johnson, R. E., and Hudson, G. E. 1976. Bird mortality at a
glassed-in walkway in Washington State. Western Birds
7:99-107.
89
Larry S. Thompson
Johnston, D. W., and Haines, T. P. 1957. Analysis of bird
mortality in October 1954. Auk 74:447-58.
Krapu, G. L. 1974. Avian mortality from collisions with
overhead wires in North Dakota. Prairie Nat. 6:1-6.
Lano, A. 1927. Great blue heron (Ardea herodias) elec-
trocuted. Auk 44:246.
Laskey, A. R. 1960. Bird migration casualties and wea-
ther conditions-Autumns 1 958-1959-1960. Migrant
31:6-65.
Lee, J. M., Jr. 1977. Bird collisions with transmission
lines-a preliminary study of a 230-kV transmission line.
MS.
Lee, J. M., Jr. 1978. Effects of transmission lines on bird
flights: studies of Bonneville Power Administration lines.
This volume.
Lee, J. M., Jr. and Meyer, J. R. 1977. 'Work plan for a
study of the effects of BPA transmission lines on bird flight
behavior and collision mortality." Bonneville Power Ad-
ministration, Portland, Oregon.
McCarthy, T. 1 973. Ocular impalement of a great horned
owl. Wilson Bull. 85:477.
McCartney, R. B. 1963. "The fulvous tree duck in Louisi-
ana." M.S. Thesis. New Orleans: Louisiana State Univer-
sity.
McKenna, M.G., and Allard, G. E. 1976. Avian mortality
from wire collisions. North Dakota Outdoors 39:(5 ): 16-18.
Myers, L. 1977. Sage grouse collisions on Ten Mile power-
line (230 kV). Unpublished memorandum, U.S.D.I. Bu-
reau of Land Management, Dillon, Montana.
Nero, R. W. 1974. Great grey owl impaled on barbed wire.
Blue Jay 32:178-79.
Ogilvie, M.A. 1967. Population changes and mortality of
the mute swan in Britain. Wildfowl Trust, 1965-66.
18:64-73.
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Mitigation Through Engineering and Habitat Modification
Perrins, C. M., and Reynolds, C. M. 1967. A preliminary
study of the mute swan, Cygnus olor. Ann. Rep. Water-
fowl Trust 18:74-84.
Peterson, R. L., and Glass, B. P. 1946. Notes on bird mor-
tality during nocturnal thunderstorms near College Sta-
tion, Texas. Condor 48:95-96.
Richardson, G. L. n.d. Raptors and powerlines. Unpub-
lished. U.S.F.S.
Rybak, E. J.; Jackson, W. B.; and Vessey, S. H. 1973.
Impact of cooling towers on bird migration. In Proceedings
of the Sixth Bird Control Seminar. eds. H. N. Cones, Jr.,
and W. B. Jackson, pp. 187-94. Bowling Green, Ohio:
Bowling Green State University.
Schiefelbein, G. F. 1977. "Alternative electrical trans-
mission systems and their environmental impact." Pre-
pared for U. S. Nuclear Regulatory Commission by Bat-
telle Pacific Northwest Laboratories.
Scott, R. E.; Roberts, L. J.; and Cadbury, C. J. 1972. Bird
deaths from powerlines at Dungeness. British Birds
65:273-86.
Sharma, R. K. 1976. Determining biological significance of
environmental impacts: Science or trans-science? In Pro-
ceedings of the Conference on the Biological Signifi-
cance of Environmental Impacts. eds. R. K. Sharma et al.,
pp. 3-10. Washington, D. C.: U. S. Nuclear Regulatory
Committee.
Siegfried, W. R. 1972. Ruddy ducks colliding with wires.
Wilson Bull. 84:486-87.
Sprunt, A., IV; Robertson, W. B., Jr.; Postupalsky, S.;
Hensel, R. J.; Knoder, C. E.; and Ligas, F. J. 19/3. Com-
parative productivity of six bald eagle populations. Trans.
N. Amer. Wild/. Nat. Res. Cont. 38:96-1 06.
Stahlecker, D. W. 1975. "Impacts of a 230-kV transmis-
sion line on Great Plains wildlife." M.S. Thesis. Ft. Collins:
Colorado State University.
91
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Stout, J., and Cornwell, G. W. 1976. Nonhunting mor_-
tality of fledged North American waterfowl. J. Wild/.
Manage. 40:681-93.
Swank, M. H. 1922. An unusual mortality among migrat-
ing Iapiand longspurs in northwestern Nebraska. Wilson
Bull. 34: 118-19.
von Bloeker, J. C. 1927. Farallon cormorant killed by an
unusual accident. Auk 44:416.
Walkinshaw, L. H. 1956. Sandhill cranes killed by flying
into powerline. Wilson Bull. 68:325-26.
Weir, R. D. 1976. Annotated bibliography of bird kills at
manmade obstacles: a review of the state of the art and
solutions. Canad. Wildl. Serv., Ontario Region, Ottawa.
Weston, F. M. 1966. Bird casualties on the Pensacola Bay
Bridge (1938-1949). Florida Nat. 39:53-55.
Whelan, P. 1 976. The bird killers. Ontario Nat. 1 6:14-16.
Willard, D. E. 1977. Testimony before the Public Utility
Commissioner of Oregon, Salem, Oregon. August 18-19,
1977.
Willard, D. E.; Harris, J. T.; and Jaeger, M. J. 1977. The Im-
pact of a Proposed 500-kV Transmission Line on Water-
fowl and Other Birds. A report for the Public Utility Com-
missioners of Oregon.
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Effects of Transmission
Lines on Bird Flights:
Studies of Bonneville Power
Administration Lines
Jack M. Lee, Jr.
Bonneville Power Administration
INTRODUCTION
Bonneville Power Administration (BPA) is the agency
within the U.S. Department of Energy responsible for
marketing power generated by federal hydroelectric dams
in the Columbia River Basin. BPA operates over 19,000
kilometers of transmission lines (115 kv-to-500 kv a.c.,
:!:400 kv d.c.) located throughout the Pacific Northwest. As
a federal agency, BPA is subject to provisions of the
National Environmental Policy Act which require that the
environmental impact of major actions be identified.
In 1974, BPA began a research program to obtain
specific information on the environmental impactoftrans-
mission facilities. The program was designed to be respon-
sive to concerns identified during the environmental
impact statement process by BPA, other agencies, and the
public. Initial research was directed at the impact of extra-
high voltage (EHV) (above 230 kv) transmission lines on
plants and animals (Goodwin 1975, Lee and Rogers 1976,
Griffith 1977). This reflected the wide interest in the
possible biological effects associated with corona and
electric and magnetic fields of EHV transmission lines. To
93
Jack M. Lee, Jr.
date, this research has shown that most impacts on wild-
life that are detectable by field observation are due pri-
marily to habitat modifications resulting from construc-
tion and maintenance operations (Lee 1977).
lnrecent years, a growing number of comments on the
possible effects of BPA transmission lines on migratory
birds have been received. These comments have been pri-
marily in the form of questions rather than reports of
observed effects. Research on the BPA system so far has
concentrated on possible effects of transmission lines on
bird distribution and abundance (Lee and Rogers 1976,
Lee and Griffith 1977, Griffith 1977) and on the use of
transmission line structures as nesting sites (Lee 1976).
Preliminary information has also been collected on the
effects of transmission lines on bird flight behavior,
including collisions with wires. This last subject has re-
ceived considerable attention in recent years, and the
need for quantitative data is generally recognized. In this
paper, I will point out the distinguishing characteristics of
transmission lines, briefly review relevant literature, and
report on studies and observations of the effects of BPA
transmission lines on bird flight behavior and collision
mortality.
TRANSMISSION LINES
Transmission lines are used to transmit electric power
from generation sources to load centers. In 1975, there
were an estimated 408,930 circuit kilometers of over-
head transmission lines (in this group 110 kv to 800 kv) in
the U.S. with EHV (345 kv to 800 kv) lines constituting
approximately 6.3 percent of this total (Edison Electric
Institute 1976). Currently, the highest voltage for opera-
tional a.c. transmission lines in the U.S. is 765 kv. BPA has
constructed a 1200-kv a.c. prototype transmission line,
and such ultrahigh voltage (above 800 kv) lines are
expected to be in use in the 1980s.
Compared with power distribution (below 115 kv) and
communication (telephone and telegraph) lines, trans-
mission lines usually have much larger support towers
and conducting wires (conductors) (Figure 1 ). At voltages
94
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Jack M. Lee, Jr.
above 345 kv, multiple conductor bundles are usually
used. For example, the 4.07-centimeter diameter con-
ductors used on high capacityBPA500-kvlines, which ace
in bundles of three for each of the three-line phases, are
over four times larger than the single conductors used on
some 12.5-kv distribution lines. The conductors on the
BPA 1200-kv prototype line are 4.07 centimeters in diam:
eter, and there are eight of them in each phase arranged in
1.1-meter diameter circular bundles. On some trans-
mission lines, one or two overhead groundwires (also
referred to as shield wires or static wires) are used for
protection against lightning. These are usually of small
diameter compared with conductors.
For EHV lines, effects from the electric and magnetic
field and from corona are more apparent than from lower
voltage lines (Lee et al. 1977). The calculated electric field
strength at conductor height at 1 meter, 10 meters, and 50
meters from the conductors of a 230-kv a.c. transmission
line is about 20 kv per meter, 1.3 kv per meter, and0.05 kv
per meter, respectively. For a 500-kv line at these
distances, these values are approximately 70 kv per meter,
4.3 kv per meter, and 0.3 kv per meter, respectively. For
comparison, the d.c. electric field strength of the earth is
about 0.1 3 kv per meter at the surface (Polk 1974).
Magnetic field strength is a function of current rather than
voltage as in the case of the electric field. At distances
greater than about 10 meters, field strength is usually of
less magnitude. than the 0.6 Gauss of the earth's d.c.
magnetic field.
Corona occurs when the electric fieJd on the surface of
a transmission line conductor exceeds the breakdown
strength of air (Deno and Comber 1975). Audible noise and
flashes of light are among the products of corona. With a.c.
transmission lines, corona is most noticeable during
inclement weather. The noise consists of a broadband
hissing, crackling component with a 120-Hz tone or
multiples of this frequency occasionally present. The
amount of audible noise produced by transmission lines
varies considerably depending on a number of factors
including weather, voltage, and conductor configuration.
With BPA's present 500-kv line design, audible noise
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during rain averages about 50 dB(A) at the edge of the
right-of-way.
LITERATURE REVIEW
Bird deaths due to collisions with powerlines have
been documented in several reports (Table 1 ).In a number
of reports, there is insufficient information with which to
determine whether the line involved was a transmission
or distribution line. Terms such as "powerlines" or "over-
head lines" are frequently used without qualification, and
the latter can include communication lines. As a compari-
son with the reports in Table 1, I found at least nine reports
which describe bird collisions with distribution lines and
five reports which do not distinguish between power and
communication lines.* It should be pointed out that in
some reports the birds found dead beneath distribution
lines may have been electrocuted. Electrocution is gener-
ally not a problem with transmission lines because of the
greater distance between conductors.
In general, reported mortality levels due to bird colli-
sions with transmission and even distribution lines are
low compared with those reported for certain other types
of obstacles (e.g., television transmitting towers) as
described in reviews by Vosburgh (1966) and Weir (1976).
Currently, it is not clear how "reported" mortality due to
collisions with various obstacles compares with actual
mortality.
Reported collision mortality due to wire strikes has
been related to other nonhunting mortality in waterfowl by
Stout and Cornwell ( 1976). In their paper, reported mor-
tality due to collisions with objects accounted for 2,299
(0.1 percent) of the 2, 1 08,880 birds in their sam pie. Of the
former number, 1,487 were reported collisions with tele-
phone and power lines. Cornwell and Hockbaum ( 1971)
have pointed out bird collisions with lines largely go un-
noticed and unreported. I believe this can probably also be
said of many other types of collisions.
*An annotated bibliography listing these reports is available from the
author.
97
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Table 1. Reports of bird collisions with transmission lines and with "powerlines" which may have included transmission and/ or
distribution lines.
Reference
Anderson
1978
Arend
1970
Scott et al.
1972
Willard et al.
1977
Blokpoel and
Hatch 1976
Gallop
1965
Krapu
1974
Stout
1967
Line Type
Two 345-kv trans-
mission lines
500-kv transmis-
sion line
Two 400-kv trans-
mission lines
230-kv transmis-
sion line
"Powerline"
"Powerlines"
"Powerlines"
"Powerlines"
Location
Central Illinois
Sutter N.W.M.A.,
Ca.
Dungeness, Great
Britain
Klamath Basin,
Oregon
Manitoba, Canada
Saskatoon, Canada
North Dakota
California
Number Birds Found
343 dead or crip-
pled waterfowl
50 ducks
1,285 birds of 74
species
12 waterfowl and
shorebirds
An estimated 25-75
snow geese
15 birds of 12
species
15 birds
235 ruddy ducks
Circumstances
Birds were found in a water-filled slag pit
near lines during the fall over a 3-year
period. Anderson estimated approximately
400 birds killed each year during fall and
winter.
Birds apparently startled into flight by
illegal hunters at night.
Birds found near three line spans between
January 1964 and November 1970. Ac-
tual number of casualties estimated at 6,000.
Birds were found at three sites during
searches conducted during fall 1976 and
spring 1977.
Light airplane startled birds into flight.
Birds found during one fall where series of
powerlines crossed sandbar.
Mortality includes Krapu's own obser-
vations over several years plus reports from
other persons.
Report did not indicate when collisions
occurred other than that losses were great-
est during foggy periods.
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Concerns have also been expressed which are some-
what contradictory to those related to the collision
potential of transmission Unes. During a court case
involving an Illinois duck hunting club and a power
company, witnesses testified that transmission lines
adversely affected waterfowl flight behavior to the extent
that birds were reluctant to fly near such lines (Anony-
mous 1968). Similar testimony was given during a 1977
court case in Washington State (United States vs. Chad-
bourne). The latter case involved a BPA 500-kv transmis-
sion line which was constructed across land leased by a
private duck hunting club. In both ofthese cases, the court,
in effect, found that a transmission line would have some
adverse influence on waterfowl flight behavior resulting in
adverse effects on waterfowl hunting near the line. The
possibility that powerlines could change waterfowl
hunting success was also suggested in a studyofthe inter-
action between birds and obstacles by Willard and Willard
(1972).
These reports and testimony raise the question as to
whether birds react to the electrical effects of transmis-
sion lines. There is evidence that birds can at least per-
ceive such effects. The rangeoffrequencies heard by most
birds is very similar to man's range(Bremond 1963), and it
is reasonable to assume that corona noise is audible to
birds. Although birds are commonly seen perched on
distribution and communication lines, I have never seen a
bird attempt to land on an energized transmission line con-
ductor. Unsuccessful landing attempts have been reported
to me on a few occasions. Graves et al. (1977) reported
that, in a laboratory test, pigeons were apparently able to
detect a 60-Hz electric field of 32 kv per meter (the lowest
field strength tested) This is the field strength at approxi-
mately 2 meters from the conductors of a 500-kv line. Two
reports have indicated birds are able to perceive electric
and magnetic a.c. fields at levels comparable to those of
the earth's d.c. fields (Southern 1975, Larkin and Suther-
land 1977).
99
Jack M. Lee, Jr.
STUDIES OF BPA TRANSMISSION LINES
Prior to the start of a study in October 1977, which is
described below, most observations of the effects of BPA
transmission lines on bird flights were made incidentally
to collecting other biological data. For example, during a
13-month study of the '±400-kv d.c. lntertie in Oregon,
Griffith (1977) observed a juvenile pintail sustain fatal
injuries by colliding with the overhead groundwire. Visi-
bility was good at the time of the collision. One of the
duck's eyes had an opaque appearance which did not
appear to have been caused by the collision. On another
occasion, Griffith and I watched a turkey vulture collide
with a conductor of a 230-kv line located adjacent to the
d.c. line. This collision also occurred when visibility was
good, although in this case the bird apparently was not
seriously injured.
Griffith's study was not specifically designed to pro-
vide information on bird collisions; however, after several
hundred hours of field observations and after traveling
hundreds of kilometers on the right-of-way access road,
he found only five dead birds, some of which may have
collided with the line. The d.c. lntertie line has metal
towers approximately 36 meters tall and two sets of 4.47-
centimeter conductors in bundles of two. The line also has
a single overhead groundwire. Most ofthe line is located in
western juniper and sagebrush, and only a few small
areas utilized by waterfowl are crossed.
I made an interesting observation while conducting
breeding bird counts on the right-of-way of two 500-kv
transmission lines in central Oregon. A golden eagle being
chased by two ravens collided with the conductors on one
of the 500-kv lines. Although the bird exhibited some
erratic flight behavior after the collision, it did not appear
to be injured. The line had two 4.07-centimeter diameter
conductors for each phase. The most extensive bird colli-
sion mortality which has been reported for a BPA trans-
mission line occurred near Portland, Oregon, and involved
a 230-kv line. This study is described below.
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Bird Collisions With a 230-kv Transmission line
On 29 January 1977 while observing bird flights near
Bybee Lake, I began finding birds between towers 7/2 and
6/6 of the BPA Ross-St. Johns 230-kv transmission line
(Figure 2). The line carries two electrical circuits (double
circuit). Between structure 6/6 and the St. Johns Sub-
station 2.5 kilometers to the southwest, there is a single
.
a a Centerline of BPA 230-kv line
o---o Centerline of PGE 115-kv line
• Dead bird
~100m
SANiTARY LANDFILL
&Om
(Avg.)
Figure 2. Approximate locations of 60 dead birds found near two
transmission lines in Oregon during periodic searches conducted from
29 January through 28 April 1977.
101
Jack M. Lee, Jr.
1.6-centimeter diameter overhead groundwire. Overall
dimensions of the steel support towers and conductor con-
figurations are shown in Figure 2. Each of the six con-
ductors is 2.7 centimeters in diameter and consists of
outer aluminum wire strands and inner steel strands. At
midspan, the lower-most conductors are approximately 20
meters above the ground. At the Bybee Lake crossing, the
lowest conductors are about 25 meters above the water.
The line was energized in 1952.
A 115-kv transmission line operated by Portland
General Electric Company (PGE) runs parallel to the BPA
230-k~ line. The 115-kv line has three 2.6-centimeter di-
ameter conductors spaced 3.8 meters apart on a
horizontal plane. The conductors are supported by wood
pole, H-frame structures which average 21 meters in
height. The conductors are approximately 16 meters
above the water at the Bybee Lake crossing. The horizontal
distance between the outermost conductors of the two
transmission lines is about 22 meters. The 115-kv line
was energized in 1974.
Bybee Lake is utilized by waterfowl, shore and water-
birds, and large numbers of gulls (primarily glaucous-
winged). The gulls and crows are attracted to a sanitary
landfill southwest of Bybee Lake. Waterfowl hunters
utilize the area and fisherman, bird watchers, and other
recreationists are present at various times.
Dead Bird Counts. Initially, 41 dead birds were found
between towers 7/2 and 6/6. It appeared the length of
time the birds had been dead ranged from a few days to
about 2 months. Additional searches between towers 7/2
and 7/1 were made on 5, 16, 19, and 26 February; 5, 12,
and 19 March; and 28 April1977. The span between 7/1
and 6/6 was searched on all these days except 16
February. The section between tower 6/6 and 6/5 was
also searched everyday except 5 February. Searches were
made between 7/3 and 7/2 only on 11 and 26 February.
Between 29 January and 28 April 1977, a total of 60
dead birds was found during the searches (Table 2). Thirty
percent of the birds had externally noticeable collision-
type damage such as broken wing bones and lacerations
about the head, neck, or breast. Twenty-one birds eventu.-
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Table 2. Identification of dead birds found between towers 7/3 and
6/5 of the BPA Ross-St. Johns 230-kv transmission line from 29
January through 28 April 1977
Species
Gull
Green-winged teal
Pintail
American coot
Ruddy duck
Western sandpiper
Great blue heron
Common crow
Mallard
Unidentifiable duck
Killdeer
Common snipe
Mourning dove
Song sparrow
Total
Number Found
29
7
7
3
2
2
2
2
60
ally could not be relocated during the dead bird searches.
Most of them were probably removed by scavengers,
although some may have been missed by searchers. Other
biases exist because an unknown number of birds
probably fell into Bybee Lake and were not found, and
others may have sustained mortal collision injuries but
were able to hide or move away from the right-of-way
before they died. Anderson (1978) estimated his dead bird
count was about 58 percent of the actual mortality, and the
corresponding estimate reported by Scott et al. (1972)was
about 20 percent.
Flight Counts. Observations of bird flights across the
spans where the dead birds were found were made on four
occasions (Table 3). These, plus observations made inci-
dentally to conducting the dead bird searches, indicated
that the heaviest gull flights were during early morning
when the birds flew south across the line to Bybee Lake
103
Jack M. Lee, Jr.
Table 3. Summary of counts of bird flights 1 across the right-of-way of
the BPA Ross-St. Johns 230-kv transmission line where dead bird
counts were made.
Between Line Structures Total
Each Flight
Direction 7/3-7/2 7/2-7/1 7/1-6/6 6/6-6/5 Direction
30 January 1977, 0700-0900
Northwest N2 82 31 N
Southeast N 547 75 N
19 February 1977, 0700-0900
Northwest 54 80 47 83
Southeast 478 253 51 68
26 February 1977, 1700-1730
Northwest 133 259 34 134
Southeast 4 11 2 5
5 March 1977, 1000-1100
Northwest 37 14 22 380
Southeast 306 29 8 143
Total
1 Approximately 77 percent of these flights were by gulls.
2
No counts made.
113
622
264
850
560
22
453
486
3,370
and the landfill and during evening when they returned to
their roosting sites to the north. Flights cdntinued across
the spans in both directions throughout the day, however,
at reduced intensities. The gull population using the
sanitary landfill appeared to number several thousand
birds. Other birds observed in smaller numbers included
ducks, crows, great blue herons, shorebirds, and pas-
serines.
I estimate that on the days counts were made, be-
tween 2,000 and 6,000 bird flights occurred across the
230-kv line betwe~n towers 7/3 and 6/5. Using a
conservative estimate of 2,000 bird flights per day and
assuming similar flight intensities in late fall, at least
354,000 bird flights occurred during the time (1 November
104
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1976 to 28 April 1977) in which the 60 birds were killed.
Tripling this latter number to 180 to allow for sample
biases mentioned above indicates roughly 0.05 percent of
the estimated total flights resulted in fatal collisions.
My data suggest the actual percentage of flights
resulting in fatal collisions probably varied by species.
However, because of the limited amount of diurnal flight
counts and a lack of data on nocturnal flights, an estimate
of such variations was not attempted. My overall estimate
is one order of magnitude smaller than that interpreted
from the data reported by Anderson ( 1978). Anderson's
data indicate an average of 1, 700 daily diurnal bird flights
during the fall of 1974 when there were an estimated 338
collision casualties. Depending on the extent of nocturnal
flights in Anderson's study area, the actual percentage of
collisions in his study may have been closer to the
magnitude estimated for Bybee Lake.
Bird Collisions. During the flight observations
(tabulated in Table 3), a gull collided with a 230-kv con-
ductor. During incidental flight observations, a shorebird
collided with the overhead groundwire. Although the gull
fell to the ground and the shorebird fell into Bybee Lake,
both were subsequently able to fly away. The frequency of
an observed collision during periods of good visibility, one
collision per 3,370 flights, is in contrast to the corre-
sponding ratio of one in 11,061 interpreted from the data
reported by Anderson (1978). Anderson reported this ratio
as one in 250,000; however, this was apparently based on
two observed collisions out of the 553,059 total flights
observed at the slag pit. Only 4 percent (22, 122) of the
birds actually flew across the transmission lines, and I
believe this latter number is the appropriate value to relate
to observed collisions.
Eighty-nine percent of the birds counted flew above the
overhead groundwire (or conductors in the span between
6/6 and 6/5) ofthe 230-kv line with most birds just clear-
ing the line. Nine percent of the birds flew under the con-
ductors of the 230-kv line, and only about 2 percent flew
between the upper and lowermost conductors. On 58 (1.7
percent) occasions, birds were observed to turn back as
they approached the line. In most cases, after flying
105
Jack M. Lee, Jr.
parallel to the line and gaining altitude, thebirdsflewover
the line.
The bird flight observations and the locations of the
dead birds suggest that of those birds which bore no
apparent collision damage, mostwere probably killed by
colliding with the 230-kv line. I hypothesize that the birds
were flying in a northerly direction with the wind (prevail-
ing wind direction was from the south during my visits to
the study area). The birds struck the line and momentum
caused most of them to fall north of the center of the right-
of-way. Although the two collisions described above
occurred when visibility was good, reduced visibility was
probably a determining factor in the fatal collisions. Clima-
tological data obtained from Portland International Air-
port (9.4 kilometers southeast of the study area) showed
that between 1 November 1976 and 29 January 1977 fog
occurred on 21 days and heavy fog (visibility 0.4 kilometer
or less) occurred on 44 days. Between 30 January and 28
April 1977 (during which only 11 dead birds were found),
fog was present on 16 days and heavy fog on 12 days.
In addition to monthly differences in collision mortal-
ity, there were large differences in the number of dead
birds found in each of the four spans of the 230-kv line
(Figure 2). The heaviest mortality, including all 21 ducks
listed in Table 2, occurred between towers 7/2 and 7/1.
This is consistent with flight observations which showed
almost all duck flights were across this span. The limited
amount of data collected on bird flights, however, does not
provide an adequate basis for explaining differences in
mortality among the spans. Related factors which may
have determined the incidence of collisions include the
proximity of the spans to. the sanitary landfill and Bybee
Lake and the presence of the overhead groundwire.
With the large number of birds flying across the two
transmission lines and with the formidable array of wires
perpendicular to a low-altitude flyway, one might expect to
find more dead birds than we did. Most birds were able to
avoid the lines even, perhaps, during night or in time of
poor visibility during the day. Through social interaction,
most gulls in the area had probably learned the location of
the transmission lines as they learned the location of the
106
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sanitary landfill. Other resident birds also were probably
quite aware of the location of the lines, at least during
times when visual cues were available. Low-level corona
noise from the 230-kv line was usually audible during my
visits to the area. It is possible that corona noise and
electric and magnetic fields may provide location informa-
tion to flying birds during periods of reduced visibility {Lee
and Griffith 1977). Whether such information is an aid to
birds in avoiding collisions with transmission lines has yet
to be determined.
WICHE Transmission Line/Bird Study
In October 1977, a 1-year study began which was
designed to provide additional quantitative data on the
effects of BPA transmision lines on bird flights and colli-
sions. This study is being conducted by James R. Meyer,
an intern with the Western Interstate Commission for
Higher Education {WICHE). Most of the field data for the
study will be obtained in three geographic areas having
two or three primary sample sites per area. These areas
have been selected to include a variety of environmental
and transmission line conditions so the factors which may
determine the kinds and magnitude of effects on birds can
be studied.
All sample sites contain some form of water or wet-
land habitat. This type of habitat frequently attracts large
numbers of birds including waterfowl. These areas and
the birds inhabiting them usually have high ecological and
social values. This study is, therefore, designed to look at
"worst-case" situations. By taking this approach, if
problem areas exist, they would most likely occur in these
situations. Therefore, an estimate of the seriousness of
the problem can be more reasonably made.
Study Areas. Sample site 1 in the Portland-Longview
study area is Bybee Lake, described above. Site 2 is near
Longview, Washington, where two 500-kv lines and two
230-kv lines cross the Columbia River. This site is used by
small to moderate numbers of ducks, and smaller numbers
of geese and swans are present at various times. Some of
the towers have red aircraft warning lights. Waterfowl
hunters use the area at times.
107
Jack M. Lee, Jr.
A second study area is the Willapa National Wildlife
Refuge on the Washington coast; the refuge contains a
115-kv wood pole transmission line. The section of line to
be studied is from U.S. Highway 101 to near the Long
Beach Substation. Two sites will be studied, each having a
different type of line construction. Most ofthe line crosses
wetland habitat, and it crosses the Bear River. Moderate to
large numbers of ducks and geese utilize the area. Some
waterfowl nesting also occurs during the spring. The
refuge is open to waterfowl hunting on certain days during
the season.
The central Washington study area extends from near
Ephrata, Washington, south to State Highway 7. Sample
site number 1 in this area is at Rocky Ford Creek, and BPA
lines at this site include a 500-kv line and two 230-kv
lines. Site 2 is in the Frenchman Hills Wasteway Area and
includes only a 500-kv line. Site3 is Lower Crab Creek and
also includes the 500-kv line. This part of Washington is
utilized by moderate to large numbers of ducks and geese
during fall and spring migration. Some waterfowl nesting
also occurs. This is also an important waterfowl hunting
area, and both public and private shooting areas are found
near the lines.
Study Methods. Data collection consists of two pri-
mary activities; dead bird counts and bird flight observa-
tions. Because few studies of this type have been
conducted, the development and evaluation of methods of
data collection and analysis are important parts of the
study. Suitable portions of right-of-way of the lines in the
primary study areas are periodically and systematically
searched for dead birds. If the habitat permits, the entire
right-of-way including a strip of adjacent land (approxi-
mately 45 meters out from the right-of-way) is searched.
Birds found are examined for cause of death, and their
location is mapped. During each search, an effort is made
to locate all birds previously found and left onsite as well
as to locate new birds. By tagging and leaving birds on the
site, information on removal and decomposition rates can
be obtained. To obtain information on recovery success, a
sample of dead birds is randomly planted at least once on
each site immediately prior to beginning regular searches
108
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for dead birds. The location and number of birds planted
are not known to the searchers.
For all sections of lines where dead bird searches are
conducted, periodic and systematic observations of bird
flights are made. Information obtained by these observa-
tions will provide a basis for interpreting the mortality
levels obtained with the dead bird counts. The following
information will be noted for all birds approaching the
section of line under observation: species or type of bird,
number in flock, direction and altitude of flight, and
behavior when approaching the line. Most flight observa-
tions will be done during daylight including some counts
from daylight to dark. Beginning in January 1978, a night
viewing device ("Javelin" model 226) will be used for
nocturnal flight observations and to observe the behavior
of predators and scavengers. A 16-mm movie camera will
be used to document the various types of flight behavior
which are typically observed in each study area.
The feasibility of various methods to remotely monitor
bird flight behavior and collisions will be studied. These
methods will include time-lapse photography,_ closed
circuit television, and devices which monitor collision
impacts with conductors or overhead groundwires.
Between22 October 1977 and 28 January 1978, each
of the three study areas will be sampled during alternat-
ing 2-week periods. From February through June 1978,
observations will be concentrated primarily in the Bybee
Lake and Central Washington study areas.
Preliminary Results. Data from the study are sti II being
collected and analyzed, so only preliminary information is
available at this time. During the initial dead bird counts
between 22 October and 21 December 1977, a total of 19
birds was found ip the three study areas along a total of
about 5 kilometers of lines.* This number included seven
green-winged teal, two red-winged blackbirds, one robin,
two mourning doves, four starlings, two glaucous-winged
gulls, and one bufflehead. Ten of these were found in the
Central Washington study area near a 0.6-kilometer long
section of the 500-kv line at the Lower Crab Creek site. All
*James S. Meyer 1978: personal communication.
109
Jack M. Lee, Jr.
but 5 of the 19 birds found had collision-type damage
detectable by field examination.
During 8 days of flight observations, Meyer saw five
ducks and three blackbirds collide with the overhead
groundwire of the 500-kv line. Five of the birds fell to the
ground and at least two of these received fatal injuries.
The collisions occurred during good visibility. During the
time period in which the collisions were observed, 17,867
birds were counted flying across the line. These data show
that, on the average, there was one collision observed for
every 2,233 flights counted. This ratio is similar in
magnitude to that described previously for the 230-kv line
at Bybee Lake. The 500-kv conductors are 3.3 centi-
meters in diameter and are in bundles of three for each
phase of the delta configuration. The two overhead
groundwires are each 9.78 millimeters in diameter.
Exact flight counts have not yet been tabulated for the
other sites; however, waterfowl flight intensities at the
Lower Crab Creek site were the highest of any of the sites
during the initial phase of the study. By making flight
observations during both day and night, Meyer expects to
express the collision mortality as a percentage of the over-
all flight intensity and species composition. The final
results of the WICH E study may indicate the need for addi-
tional research including the need todevelop measures to
mitigate adverse effects.
DISCUSSION AND CONCLUSIONS
Experience with BPA transmission lines indicates such
lines can affect bird flights and that birds at times collide
with conductors or overhead groundwires. To date, how-
ever, I am not aware of situations where BPA transmis-
sion lines represent a significant avian mortality factor.
Only preliminary data currently exists for basing such
conclusions, so any such conclusions must be considered
tentative. Until more definitive information is available, it
seems reasonable to consider the potential for bird strikes
when evaluating the impacts of transmission lines. This is
especially so if areas utilized by threatened or endangered
birds may be affected. Even relatively small increases in
110
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mortality from whatever source may be significant when
these kinds of birds are involved.
Based on studies of BPA lines and on my review of the
literature on bird collisions with powerlines and other
obstacles, it appears that several factors need to be con-
sidered when predicting the effects of existing or planned
transmission lines on birds (Table 4). Currently, informa-
tion with which to evaluate the relative importance of
these and other factors in determining the incidence of
bird collisions with transmission lines is extrem,ely limited.
For example, little is known about whether the structural
and electrical differences between transmission lines and
other types of utility lines also result indifferent effects on
birds. Therefore, I believe it is not desirable to attempt to
predict impacts of transmission lines on birds by using
information based only on observations of distribution or
communication lines. It may well be that the larger size of
the transmission line conductors and the electrical fields
and noise which they produce combine to decrease the
potential for bird collisions-especially during the critic.al
times when visibility is poor. It also appears that the pres-
ence of one or more small diameter overhead groundwire
on a transmission line may greatly increase the potential
for bird collisions. For all studies and reports involving
transmission lines and birds, it is, therefore, important
that details of the lines be given along with information on
pertinent environmental conditions. As a minimum,
information should be given on the number and voltage of
all lines present and the size and number of conductors
and overhead groundwires. For all studies involving dead
bird counts, information on bird flight intensities,
altitudes, timing, and species composition during the time
the mortality occurred should be provided.
As a biologist, I am concerned with all sources of avian
mortality. As a biologist for a power marketing agency, I
devote most of my research efforts toward identifying the
mortality associated with transmission lines. I believe that
collision mortality should be considered in relation to other
possible adverse effects of transmission lines (e.g.,
increased vulnerability of birds using towers to illegal
shooters) and to possible beneficial effects (e.g., use of
111
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Table 4. Factors which may determine the number of bird collisions expected with a transmission line during some specific period.
General Category
Bird biology
Flight
Transmission line
Environment
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Factor
Species
Age
Health
Migration
Sex
Flight intensity
Altitude of flights
Size of flocks
Time of flights
Tower type
Voltage
Conductor characteristics
Number of lines
Overhead ground wire
Line length
Age of line
Aircraft warning lights
Weather
Habitat
Human activity
Geographical location
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Suspected High Collision Risk Situations
Nocturnal fliers or those with awkward flight characteristics
Immature birds with limited flight experience
Sick or injured birds
Migrants as opposed to resident birds
Birds involved in nuptial displays
Large numbers of birds crossing the right-of-way during all times of day
Altitudes equal to or lower than the uppermost wires
Large flocks with small spacing between birds
Nocturnal flights and diurnal flights durin~ inclement weather
Guyed structures or tall towers near river crossings
Lower voltage lines with reduced electric field and corona effects
Small diameter, single conductor/phase configurations
Double-cirucit lines with wire at different heights
Multiple wires small in diameter compared with conductors
A long line through a high-use area
A newly constructed line before birds can habituate
Nonflashing lights on towers in established flyways
Fog, snow, rain, sleet, or high winds
Attractive bird habitat on and surrounding the right-of-way
Hunting and other human activities which startle or distract birds
Lines located perpendicular to a narrow, low-altitude flyway
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towers by birds for perching and nesting). Although there
is a need for research on the effects of transmission lines
on birds, this need also applies toothertypes of utility lines
and perhaps even to other types of man-made structures.
For transmission lines, at least, a goal should be to develop
models with which to predict the impact of existing and
proposed lines on birds with some degree of confidence.
This will require multidisciplinary studies conducted in a
variety of environmental settings which include the
various types and configurations of lines.
Research may reveal areas where significant mor-
tality (whether defined in a political or ecological context)
is occurring as a result of birds colliding with transmission
lines. Likewise, in some areas, transmission lines may
affect local flight patterns. In the case of waterfowl, effects
on flight behavior may result in either increased or
decreased waterfowl mortality if waterfowl hunting
success near the lines is changed. Until information
derived from sound research is available, utilities may be
reluctant to expend the effort and funds to develop means
to mitigate suspected adverse effects. Likewise, until
information is available on the effects of existing trans-
mission I ines on birds, decisionmakers may be reluctantto
commit financial resources to minimize potential effects
on birds when new transmission lines are designed and
located.
ACKNOWLEDGMENT
I wish to thank Anthony R. Morrell and Dennis B.
Griffith for assisting me in collecting field data during the
study of the 230-kv I i neat Bybee Lake and for reviewing an
early draft of this paper. My thanks also to Dr. T. Dan
Bracken and James R. Meyer for their review of a draft of
this paper. Dr. Bracken also provided the calculated
electric field strengths cited in this paper. I appreciate the
assistance of James Meyer for providing me with prelim-
inary results from his study.
113
Jack M. Lee, Jr.
REFERENCES
Anderson, W. L. 1978. Waterfowl collisions with power
lines at a coal-fired power plant. Wildlife Society Bull. ·In'
press.
Anonymous. 1968. Central Illinois Light Company vs. ·
Mary Allen Porter et al. 239 North Eastern Reporter. 2d.
298-301.
Arend, P. H. 1970. TheEcologicallmpactofTransmission
Lines on Wildlife of San Francisco Bay. Report by Wildlife
Associates to Pacific Gas and Electric Company of San
Ramon, California.
Blokpoel, H., and Hatch, D. R. M. 1976. Snow geese, dis-
turbed by aircraft crash into powerlines. Canad. Field-Nat.
90:195.
Bremond, J. C. 1963. Acoustic behavior of birds. In
Acovstic Behavior of Animals. ed. R. G. Busnel, pp. 709-
50. Amsterdam: Elsevier Publishing Co.
Cornwell, G. A., and Hochbaum, H. A. 1971. Collisio·n·s
with wires-a source of anatid mortality. Wilson Bull.
83:305-6.
Deno, D. W., and Comber, M. G. 1975. Corona phenom-
ena on a.c. transmission lines. In General Electric Com-
pany: Transmission Line Reference Book 345-kV and
Above, pp. 122-48. Palo Alto, California: Electric Power
Research Institute.
Edison Electric Institute. 1 976. Statistical Year Book of the
Electric Utility for 19 7 5. New York: Edison Electric
Institute.
Goodwin, J. G., Jr. 1975. Big Game Movement Near a
500-kV Transmission Line in Northern Idaho. A Study by
the Western Interstate Commission for Higher Education
for the Engineering and Construction Division, Bonneville
Power Administration, Portland, Oregon.
Gallop, M. A. 1965. Bird migration collision casualties at
Saskatoon. Blue Jay. 23:15-17.
114
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Studies of Bonneville Power Administration Lines
Graves, H. B.; Carter, J. H.; Kellmel, D.; Cooper, L.; Pozna-
niak, D. T.; and Bankoske, J. W. 1978. Perceptibility and
electrophysiological response of small birds to intense 60-
Hz electric fields. Paper presented at the IEEE Power En-
gineering Society Summer Meeting. July 17-22. Mexico
City. To be published.
Griffith, D. B. 1977. Selected Biological Parameters Asso-
ciated with a -}:.400-kV d. c. Transmission Line in Oregon.
A Study by the Western Interstate Commission for Higher
Education for the Engineering and Construction Division,
Bonneville Power Administration, Portland, Oregon.
Krapu, G. L. 1974. Avian mortality from collisions with
overhead wires in North Dakota. Prairie Nat. 6:1-6.
Larkin, R. P., and Sutherland, P. J. 1977. Migrating birds
respond to Project Seafarer's electromagnetic field.
Science 195:777-79 .
Lee, J. M. Jr. 1976. A Study of the Effects of BPA Trans-
mission Structures on Raptors and the Experimental
Installation of Raptor Nesting Platforms: A Project
Description and Environmental Analysis. Report avail-
able from the Engineering and Construction Division
Environmental Coordinator's Office. Bonneville Power
Administration, Portland, Oregon.
Lee, J. M.,Jr. 1977. Transmission lines and their effects on
wildlife: A status report of research on the BPA system.
Paper presented at the Annual Meeting of the Oregon
Chapter of the Wildlife Society. Kah-Nee-Ta, January 20,
1977. Paper available from the author.
Lee, J. M., Jr., and Griffith, D. B. 1977. Transmission line
audible noise and wildlife. Paper presented at the Ninth
International Congress on Acoustics, Madrid, Spain, July
3-9, 1977. In press.
Lee, J. M., Jr., and Rogers, L. E. 1976.Biological studies of
a 1200-kV prototype transmission line near Lyons, Ore-
gon. Quarterly Progress Report No. 1. Report on file in the
Engineering and Construction Division Environmental
Coordinator's Office. Bonneville Power Administration,
Portland, Oregon.
115
Jack M. Lee, Jr.
Lee, J. M.,Jr.; Bracken, T. D.; Capon, A. S.; Sarkinen, S. H.;
lhle, G. M.; Perry, D. E.; and Eyler, T. R. 1977. Electrical and
biological effects of transmission lines: a review. Bonne-
ville Power Administration, Portland, Oregon.
Polk, C. 1974. Sources, propagation, amplitude, and tem-
poral variation of extremely lowfrequency(0-1 00 Hz) elec-
tromagnetic fields. In Biological and Clinical Effects of
Low-Frequency Magnetic and Electric Fields, eds. Llau-
rado, J. G., et al. pp. 21-48. Springfield, Illinois: Charles C.
Thomas.
Scott, R. E.; Roberts, L. J.; and Cadbury, C. J. 1972. Bird
deaths from powerlines at Dungeness. British Birds
65:273-86.
Southern, W. E. 1975. Orientation of gull chicks exposed
to Project Sanguine's electromagnetic field. Science
180: 143-45.
Stout, I. J. 1967. "The nature and pattern of non-hunting
mortality in fledged North American waterfowl." M.S.
Thesis. Vir. Poly. lnst. and State University, Blacksburg.
Stout, J., and Cornwell, G. W. 1976. Nonhunting mor-
tality of fledged North American waterfowl. J. Wild!.
Manag. 40:681-93.
Vosburgh, J. 1966. Deathtraps in the flyways. In Birds in
Our Lives, eds. A. Stefferud and A. N. Nelson, pp. 364-71.
Washington, D.C.: U.S. Fish and Wildlife Service.
Weir, R. D. 1976. Annotated bibliography of bird kills at
man-made obstacles: A review of the state of the art and
solutions. Dept. Fish Env., Env. Manag. Serv., Canad.
Wildl. Serv., Ontario Reg., Ottawa.
Willard, D. E.; Harris, J. T.; and Jaeger, M. J. 1977. The
Impact of a Proposed 500-kV Transmission Line on
Waterfowl and Other Birds. A report for the Public Utility
Commissioner of Oregon.
Willard, D. E.; and Willard, B. J. 1972. The Interaction
Between Some Human Obstacles and Birds. A rep~rt ~y
the Institute for Environmental Studies, University of
Wisconsin, Madison.
116
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Evaluation of a Proposed
Transmission Line·s
Impacts on
Waterfowl and Eagles
Roger L. Kroodsma
Environmental Sciences Division
Oak Ridge National Laboratory
INTRODUCTION
This paper summarizes an environmental assessment
of the potential impacts of a proposed transmission I ine on
waterfowl and bald eagles. This transmission line would
be one· of three 345-kv lines servicing the nuclear-
powered Tyrone Energy Park (TEP), which is proposed by
the Northern States Power Company (NSP) to be con-
structed near Eau Claire, Wisconsin. The line would cross
the Mississippi River just north of Red Wing, Minnesota,
through important waterfowl and bald eagle habitat. The
U.S. Nuclear Regulatory Commission (NRC) has reviewed
NSP's application to construct TEP, has prepared a Final
Environmental Statement (NRC 1977), and has com:
pleted public hearings. The Wisconsin Public Service
Commission is presently reviewing the TEP application.
As an ecologist, I was a reviewer for the NRC and pre-
pared the portions of the Environmental Statement deal-
ing with impacts of transmission lines. The purpose of this
paper is to discuss potential impacts of transmission lines
on migratory waterfowl and eagles, to present the TEP
117
Roger L. Kroodsma
case as an example problem, and to suggest possible miti-
gation techniques and needed research.
POTENTIAL IMPACTS
The potential impacts of transmission lines on both
waterfowl and bald eagles include mortality due to colli-
sions (not electrocution) with lines and towers and distur-
bance of important habitat (e.g., eagle nest sites, impor-
tant waterfowl resting and feeding areas). Electrocution is
not considered a problem with high voltage transmission
I ines (in contrastto the smaller distribution I ines), because
conductors are far enough apart to prevent simultaneous
contact of a bird's extremities with adjacent conductors.
Waterfowl collisions with lines appear to be respon-
sible for a very small fraction of hunting and nonhunting
mortality. Nationwide data reported by Stout and Corn-
well ( 1976) indicates that about 0.07 percent of non-
hunting mortality results from collisions with lines. This
figure includes data not only for transmission lines, but
also for the smaller distribution lines and telephone wires.
Thus, deaths caused by transmission lines would appear
to have had np significant impact on waterfowl popula-
tions. As transmission lines proliferate, however, impacts
will increase and become of more concern. Most collision
mortality probably occurs near breeding, feeding, or rest-
ing areas where birds fly low. On long-distance migratory
flights and flights between feeding and resting areas,
flocks generally fly high enough that collision with lines is
unlikely. As far as disturbance of waterfowl is concerned,
a few observers (no published accounts as far as I know)
believe that large transmission lines cause some avoid-
ance of habitats within roughly 0.25 mile of the lines.
For eagles, collision with power I ines would not seem to
be a problem, because the species has keen sight, flies
relatively slowly, and maneuvers well. However, if eagles
often fly during poor visibility (e.g.,. fog, dusk), collision
potential is increased. Also, because of their hunting
behavior, eagles may not always be attentive of power-
lines.Several papers (Table 1, Beecham and Kochert 1975)
have reported deaths of eagles due to collisions with
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powerlines. The type of lines usually involved have appar-
ently been distribution lines, with which electrocution
would also have been a possibility. Mortality data for
immature and adult bald eagles indicate that about 10
percent of the known deaths from 1960 through 1972
resulted from impact injuries, many of which resulted
from collisions with power lines (Table 1 ). Authors ofthese
papers, however, stated in personal communications with
me that electrocution may have, in fact, accounted for
some, if not most, of these "collision" deaths. Electrocu-
tion may have been mistakenly omitted as the cause of
death because of the lack of obvious electrocution burns.
Thus, it appears that collision with lines may not account
for as large a fraction of mortality as the literature reports.
The effect of disturbance caused by the presence of
powerlines in important habitats would probably be more·
critical in breeding areas than in nonbreeding areas.
Assuming that eagle breeding activity is relatively sus-
Table 1. Mortality of fledged bald eagles in the United States.
Years
Source Total Percent
1960-65 1966-68 1969-70 1971-72
Shot 45 28 18 13 104 47
Unknown 1 18 20 3 4 45 20
lmpact2 7 10 4 1 22 10
Poisoning 1 1 7 14 23 10
Electrocution 1 2 2 1 6 3
Trapped 2 2 1 0 5 2
Miscellaneous 2 6 4 4 16 7
1 No diagnosis could be made on the basis of autopsy findings.
2 Impact injuries resulted from the eagles striking some object,
frequently a powerline or tower (the sources below gave no more break-
down for impact).
Sources: Beliste et al. 1972, Coon et al. 1970, Cromartie et al.
1975, Mulhern et al. 1970.
119
Roger L. Kroodsma
ceptible to disturbance, one !llight conclude that the prox-
imity of transmission lines would adversely affect eagle
reproduction. However, many other raptor species have
been observed nesting in transmission line structures, pri-
marily where other suitable nest sites were not available.
Raptors in general seem to become accustomed to vari-
ous man-made structures, and their use of habitat may not
be greatly disturbed by nearby transmission lines. Never-
theless, effects on rare or endangered raptors, such as
eagles, should receive attention.
THE TYRONE ENERGY PARK CASE
One of the 345-kv lines of the TEP is proposed to run
west from the plant, cross the Mississippi River, and con-
nect with the existing Prairie Island Nuclear Station on the
west bank of the river about 5 miles north of Red Wing,
Minnesota (Figure 1 ). This region of the Mississippi River,
like much of the river, is used by large numbers of migrat-
ing waterfowl and bald eagles. An assessment of the
potential impacts of a powerline crossing the Mississippi
River in this area was needed for the environmental
impact statement. Initially, NSP proposed two possible
routes ("proposed" and "lock and dam,"see below). One
route passed near a wetlands complex of about 1100 acres
(Gantenbein Lake and associated wetlands, see Figure 1)
that is heavily used by migrating waterfowl, while the
other passed through the wetlands complex. The Ganten-
bein wetlands constitute a private hunting preserve which
is managed to attract waterfowl, and in hunting season it
is hunted only every other morning every other week. Dur-
ing the NRC review of the NSP application, several other
alternate routes were investigated by both groups as
described below.
As seems to be the case in most environmental assess-
ments, there was less information available on which to
assess the impacts and identify the best route than an
ecologist would like. Concentrations of overwintering
eagles had been observed at several sites along the Mis-
sissippi River near Prairie Island, and the number in each
area had been estimated. Also, 15 or 20 eagles had occa-
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Evaluation of Proposed Line's Impacts
sionally been seen in a forested area at dawn and dusk,
indicating the birds roosted there. However, the exact
roost site had not been sought or located. Frequency of
migrating eagles in the area had not been documented.
Eagles were not known to inhabit the area during late
@~tmf~f:~ Highground
:-:·:·:::: Wetlands
Prairie Island
Figure 1. Proposed and alternate routes crossing the Mississippi River
and leading to the existing Prairie Island Nuclear Station. Solid lines
show existing transmission lines. Double-dashed lines represent possible
routes to Prairie Island, including the proposed route at Sturgeon Lake,
the lock and dam route at Lock and Dam No. 3, the Trenton route at
Diamond Island, and the Red Wing route at Red Wing.
121
Roger L. Kroodsma
spring and summer. Numbers of migratory waterfowl fre-
quenting various wetland sites in the area had not been
documented. However, the number of each species pass-
ing through the Mississippi Flyway in this region (Table 2)
could be roughly estimated from Bellrose (1976). A small
fraction of this number of birds would be expected to occur
near Prairie Island. Personsfamiliarwith the area believed
that much larger numbers of waterfowl frequented the
Gantenbein wetlands than other wetlands in the area. In
an attempt to characterize waterfowl distribution in the
area, NSP personnel prepared a map of the region within
which alternate routes were located. The map was based
on study of aerial photographs and showed locations of
wetlands and forests. Also shown were major waterfowl
use areas and local flight lanes as determined from per-
sons familiar with the area. Additionally, NSP personnel
determined from aerial photos the height of trees along
various routes; this was done with the idea of routing the
lines at or below treetop height through or adjacent to
forests so waterfowl would pass over the structures and
avoid collision.
Four routes across the Mississippi River were
examined in detail. Each route had advantages and dis-
advantages, but no route appeared obviously superior in
terms of overall impact on wildlife, vegetation, land use,
and people.
Proposed Route
The proposed route, passing west through the Mis-
sissippi Valley, would first cross about 0.7 mile of bottom-
land forest interspersed with wetlands. Here the line span
would be reduced from the normal1200feetto 500feetto
minimize the height of the lines and towers. The towers
would be only about 70 feet high (normally they would be
94 feet or more), which approximates the height of the
taller trees in the area. To maximize the advantage of
reduced line height, the lines would be routed through or
adjacent to forest wherever feasible rather than through
the middle of wetlands. The reason is that as waterfowl
and eagles fly over the forest, they would pass over and
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Evaluation of Proposed Line's Impacts
above the towers and lines, thereby avoiding collision.
Also, the line might be less of a visible disturbance if it
were in or adjacent to the forest. After crossing this area,
the line would cross the Mississippi River channel (0.3
Table 2. Estimated numbers of waterfowl passing through the Min-
neapolis-Prairie Island-Red Wing region during spring and fall.
Species Number Corridor Statusa
Whistling swan 30,000-60,000 1
Snow goose 50,100-100,000 3(fall)
0-1,000 0 (spring)
Canada goose
Small races 500-2,500 5
Larger races 15,100-50,000 3
American widgeon 201,000-400,000 2 (fall)
Gadwall 11,000-25,000 4
Green-winged teal 2,000-25,000 5
Mallard 201,000-375,000 4
Black duck 1 ,000-10,000 5
Pintail 10,000-75,000 5
Blue-winged teal 501,000-750,000
Shoveler 2,000-15,000 5
Canvasback 51 ,000-1 00,000 1
Redhead 40,100-100,000 2
Ring-necked duck 36,000-60,000
Greater scaup 0-500 0
Lesser scaup 76,000-250,000 2
Bufflehead 2,100-4,000 4
Common goldeneye b
Hooded merganser b
Red-breasted merganser b
Common merganser b
Ruddy duck 30,100-60,000
acorridor status is the rank of the migratory corridor through the
Prairie Island region as compared with other corridors, according to five
categories of decreasing species abundance from one to five.
b No recognized corridors.
Source: Bellrose 1976.
123
Roger L. Kroodsma
mile wide) to a narrow spit of forested land separating the
channel from Sturgeon Lake. The line would then cross
Sturgeon Lake (0.4 mile wide) to the west shore where the
existing Prairie Island Plant is located. This route is the
only one that crosses a lake. Sturgeon Lake is used con-
siderably by diving waterfowl. Towers roughly 200 feet
high would be required on the east channel bank, on the
spit, and on the west shore of Sturgeon Lake. These tall
towers and lines over open water would be a collision haz-
ard to both waterfowl and eagles. Just to the south of this
route are the Gantenbein wetlands, which are heavily
used by migrating waterfowl. Almost all of these wet-
lands lie more than one-third of a mile from the proposed
route; because of this distance a powerline through this
route may have little impact on waterfoWl's use of this
area. However, major waterfowl flight lanes connecting
with the wetlands pass over this route. Therefore, colli-
sion with lines on the proposed route is a potentially seri-
ous problem, unless flights are usually high enough at this
distance from the wetlands that collisions are unlikely. In
summary, the major disadvantages of this route are the
proximity tq the high waterfowl use area and the crossing
of Sturgeon Lake. An advantage of the proposed route is
that eagles do not frequently use this particular area.
Lock and Dam Alternate
The lock and dam route passes near the center of the
Gantenbein wetlands. Therefore, it is considered an unac-
ceptable route. The only advantage of this route is that the
lines would need to cross only the river channel, and this
crossing would be adjacent to a lock and dam witt;! some
existing tall structures.
Trenton Alternate
The Trenton alternate would cross the Mississippi
River below the lock and dam and pass-through much for-
ested land in the Mississippi Valley(The primary advan-
tage of this route is that it is distant from the high water-
fowl use area. Also, much of the line could pass through,
or adjacent to, forest (using short spans as in the pro-
posed route) thereby reducing collision potential for
124
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waterfowl and eagles. The major disadvantages are that
the river crossing is located in a relatively major eagle use
area compared with other areas along the river and that
evidence indicates there is an eagle roost somewhere in
the forest in this area. Wintering eagles are apparently
attracted to this area because the river remains open
longer than at many other areas.
Red Wing Alternate
The Red Wing alternate crosses the Mississippi River
adjacent to Red Wing, Minnesota. Its primary advantage
would be little impact on waterfowl. The line would pass
primarily near areas of human disturbance (residential,
commercial, and industrial areas and corridors with exist-
ing transmission lines) where waterfowl are relatively
scarce. Disadvantages are that the line would use more
land with a relatively high dollar value, would be near and
visible from several residential areas, would cross the
Mississippi River in an area having a wintering eagle con-
centration equal to that at the Trenton crossing, and would
be from 3 miles to 5 miles longer than the proposed route.
Conclusion
Selecting one of these four routes involves various
tradeoffs: waterfowl versus eagles, waterfowl versus
people, and waterfowl versus economic costs. The Tren-
ton route' might have minimal impact on waterfowl and
people but greater impact on eagles than the proposed
route. If the potential for eagle collisions with powerlines
is low enough to be of little concern, the Trenton route
might be the best. This potential, however, is not well
known. The NRC staff has concluded that no route has
obvious overall advantage in terms of wildlife, environ-
ment, aesthetics, and land use. This conclusion has been
presented to the NRC Atomic Safety and Licensing Board
for Tyrone, which is an NRC decisionmaking body. As of
this writing, the Board has not yet ruled on the Tyrone
application.
125
Roger L. Kroodsma
RESEARCH NEEDS
For site-specific cases where a proposed line would
pass near important waterfowl or eagle habitats, the
following information should be obtained for use in route
determination: local distribution, including population
estimates; flight patterns; and flight height. This informa-
tion should be provided by species, season oft he year, and
daytime and nighttime periods, as appropriate.
In general, better knowledge of waterfowl and eagle
behavior would have helped this assessment of impacts,
route selection, and possible mitigation. Knowledge of the
height above treetops at which waterfowl and eagles fly
during short-distance flights would help determine the
value of reducing tower and line height and routing
through or adjacent to forest. Information is needed on the
extent to which waterfowl and eagles fly at low altitudes or
fly to and from resting and feeding areas during poor visi-
bility (e.g., fog and darkness). Use of habitats near lines
should be studied to determine the degree to which lines
disturb waterfowl and eagles.
Also useful would be studies of mortality at existing
lines. For a waterfowl breeding population or migratory
flock using a given area containing a powerline, the frac-
tion lost due to collision should be determined. Such a
study would require both estimates of the number of
waterfowl susceptible to collision and the actual number
that collide. The number killed by a particular length of line
is generally very difficult to determine because of the diffi-
culty of finding dead birds in dense vegetation, predator
removal of dead birds, and escape of injured individuals
that die later. Because of these difficulties, accurate esti-
mates would require intensive searches, possibly with the
use of trained dogs, and experiments to determine rates of
predator removal. Vibration detection devices should be
investigated and developed for use in detecting collisions
of birds with powerlines.
Finally, the effectiveness of mitigation techniques
should be investigated. Such techniques would include
reducing line height and routing through or adjacent to
forest, using horizontal instead of vertical configurations
126
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of conductors so that less vertical flying space is occupied
and conductors can more readily be seen by approaching
waterfowl, marking lines in various ways for better visi-
bility, and routing lines parallel to existing transmission
lines and other structures.
ACKNOWLEDGMENT
Oak Ridge National Laboratory is operated by Union
Carbide Corporation for the U.S. Department of Energy.
Research forth is article was supported by the U.S. Nuclear
Regulatory Commission under Interagency Agreement
DOE 40-544-75.
I wish to thank R. B. Craig, L. D. Voorhees, and E. G.
Struxness for providing helpful comments on the manu-
script.
REFERENCES
Beecham, J. J., and Kochert, M. N. 1975. Breeding biology
of the golden eagle in southwestern Idaho. Wilson Bull.
87:506-13.
Belisle, A. A.; Reichel, W. L.; Locke, L. N.; Lamont, T. G.;
Mulhern, B. M.; Prouty, R. M.; DeWolf, R. B.; and
Cromartie, E. 1972. Residues of organochlorine pesti-
cides, polychlorinated biphenyls, and mercury and autopsy
data for bald eagles, 1969 and 1970. Pestic. Manit. J.
6:133-38.
Bellrose, F. C. 1976. Ducks, Geese. and Swans of North
Amenca. Harrisburg, Pennsylvania: Stackpole Books.
Coon, N. 0.; Locke, L. N.; Cromartie, E.; and Reichel, W. L.
1970. Causes of bald eagle mortailty, 1960-1965. J. Wild/.
Dts. 6:72-76.
Cromartie, E.; Reichel, W. L.; Locke, L. N.; Belisle, A. A.;
Kaiser, T. E.; Lamont, T. G.; Mulhern, B. M.; Prouty, R. M.;
and Swineford, D. M. 1975. Residues of organochlorine
pesticides and polychlorinated biphenyls and autopsy data
forbald eagles, 1971-72. Pestic. Manit. J. 9:11-14.
127
Roger L. Kroodsma
Mulhern, B. M.; Reichel, W. L.; Locke, L. N.; Lamont, T. G.;
Belisle, A.; Cromartie, E.; Bagley, G. E.; and Prouty, R. M.
1970. Organochlorine residues andautopsydatafrombald
eagles, 1 966-68, Pes tic. Manit. J. 4:141-44.
Stout, I. J., and Cornwell, G. W. 1976. Nonhunting mor-
tality of fledged North American waterfowl. J. Wild/.
Manage. 40:681-93.
U.S. Nuclear Regulatory Commission. 1977. Final
Environmental Statement Related to the Construction of
Tyrone Energy Park. NUREG-0226, Docket No. STN-484.
128
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Transmission Line
Engineering and
Its Relationship to
Migratory Birds
W. Allen Miller
Tennessee Valley Authority
INTRODUCTION
In addition to its charge to provide electric power for the
Tennessee Valley region, the Tennessee Valley Authority
has a broad commitmenttocoordinated resource develop-
ment. While some of TVA's programs actively promote
migratory bird life -particularly waterfowl -TVA's
power transmission system probably has the potential, in
some places, to harm birds. Although there have been no
reports of significant collision-related bird mortalities in
the TVA service region, TVA has attempted to address the
potential for bird collisions in a positive manner, prevent-
ing the problem or mitigating its seriousness, primarily by
balanced location of transmission routes. No extensive
research programs have been undertaken within TVA as
of the date of this conference to attempt an assessment of
the causes and extent of any bird deaths.
This paper will not be an attempt to provide pat
answers to the questions before this conference. hs
purpose is to introduce to the conference some of the
procedures and constraints controlling the development of
TVA's transmission lines and TVA's attitudes and efforts
129
W. Allen Miller
with respect to resident and migratory birds. This discus-
sion will identify meaningful areas of flexibility in trans-
mission engineering. If this conference concludes that a
problem exists with respect to birds colliding with
transmission lines, thesewilllikelybesomeoftheareas in
which the solutions will be sought.
Transmission engineering is a multifaceted operation
encompassing network load flow analysis, system
planning, facility location, design construction, and opera-
tion. The only two distinct transmission engineering
operations which could have an influence on the potential
for bird collisions are transmission route selection and
transmission line design.
TRANSMISSION ROUTE SELECTION
The route selection process begins with identifying the
need for a transmission line. Each transmission line built
is designed to meet a specific need. There are different
types of transmission need. Some lines are built to
transfer fixed levels of power from point to point. Some are
dedicated to serve variable loads. Others may be built
entirely to reinforce the transmission network or provide
interconnections with other power systems.
There is a great deal of variety in the degree to which
the terminal ends of needed transmission lines are
geographically established. Some conditions may permit
considerable flexibility in choosing potential transmission
routes. while oth~r lines may be narrowly constrained.
In a broad sense, the costs of alternafive routes help to
define the study area. Good planning will eliminate
unnecessary distance, minimize the use of expensive
angle structures, and avoid land where social costs would
be excessively high. These cost considerations, however,
are not all the criteria used to select transmission line
routes. Economic considerations are balanced against the
extremely weighty environmental considerations -
among them, habitats and flyways of migratory birds.
Significant environmental issues which can be quantified
might dictate, for example, that a route simply bypass a
critical location, despite increased construction costs. The
130
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Engineering and Migratory Birds
principal efforts in route planning are to eliminate or
diminish possible land use and visual conflicts, avoid
sensitive natural areas, and yet remain responsive to the
engineering costs and requirements of the job.
The methods used to identify and evaluate alternative
transmission routes involve field reconnaissance and
mapping procedures along with consultation and co-
ordination with public representatives. Natural and man-
made features in the study area a~e examined and
analyzed for relationships to transmission line location.
Information is gathered from various sources within TVA;
municipal officials; federal, state, and regional agencies;
and from any other sources available. U.S. Geological
Survey 7.5-minute series topographic maps are
commonly used as a base to organize geographically
referenced data for display and analysis. Tentative routes
which generally best avoid conflicts are then selected.
These tentative routes are often modified and refined by
field surveys which identify smaller scale conflicts.
The process of selecting a proposed route is one of
adjustment, accommodation, and "fitting-in," and in this
process the early identification of potential conflicts is
paramount. Land use conflicts are a prime consideration
in transmission line location. Heavily urbanized areas and
areas of dense residential development obviously pose the
most immediate land use conflicts. New TVA trans-
mission lines located through these areas have a high
priority placed on the use of existing utility corridors and
the reduction of visual impacts. Undeveloped industrial
sites, the value of which often lies in the unencumbered
state of large parcels of land, are often avoided as well,
when site development cannot be ascertained.
In areas where unique wildlife or plant habitats might
be harmed by construction activities or the continued
presence of a line or right-of-way, routes are generally
chosen to avoid the more sensitive locations. Care is taken
to review projects against cataloged information systems
operated by the various state and federal agencies, and the
r'outes are closely reviewed by TVA staff biologists,
historians, and archaeologists.
The Tennessee Valley region is liberally endowed with
131
W Allen Miller
parks, recreation areas, and wildlife management areas. It
is essentially impossible for an agency assigned the
responsibility of serving area electric needs to state
categorically that it will completely avoid these areas.
TVA's record will show that a reasonable effort has been
made to avoid these areas, and where it was impossible to
avoid them, that TVA has worked with any other parties
involved to create the least possible environmenta
impact.
TRANSMISSION LINE LOCATION EXAMPLE
This location example will serve to illustrate TVA's
efforts to minimize conflicts and impacts in potentially
sensitive areas and show how these unavoidable situa-
tions can occur. This example involves a proposed trans-
mission line to supply power to an industrial plant at
Decatur, Alabama, in 1974 (Figure 1 ).
The situation, very briefly, was this: The city of Decatur
had developed along the south shore of Wheeler Lake. On
the north side of the reservoir is a small airport in an area
of prime industrial and commercial development potential;
this area was mostly open farmland at the time of the
study. Between the city and this developing area, along the
north shore of the lake, is a wooded green belt approxi-
mately 1 mile in width and projecting for a wayupsomeof
the inlet creeks. This green belt consists of Wheeler
National Wildlife Refuge and the Swan Creek Wildlife
Management Area, together totaling over 37,000 acres.
General Motors was locating a new plant in this indus-
trializing area near the airport. The transmission line to
supply power to the plant lay some 4 miles away across
two major four-lane highways and a railroad. The plant
operations required a high degree of reliability of electric
power supply. For this reason a loop line-actually two
lines -was required so the plant could eventually be
supplied power from either direction on the existing 161-
kv transmission line. The power requirements of the plant
were phased so that only one line was required initially.
That is the essence of the situation. The primary factors
influencing the location of a 161-kv loop line to General
Motors were these:
132
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Engineering and Migratory Birds
Atrport. The line had to be kept far enough away
so that it would not encumber the airspace and
emergency glide paths.
2. Development Potential. Most of the open land
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Figure 1. Route location example: Huntsville to Decatur, Alabama,
161-kv transmission line loop to General Motors.
133
W. Allen Miller
near the highways and airport had been designated
by local planning authorities for industrial and
commercial development. The value of these prop-
erties lay in the unencumbered state ofthese large
expanses of land. The spatial arrangements of
future plants or shopping centers were unpredict-
able, and it was impossible to guarantee in advance
there would be no conflicts. Some development
had already occurred, and functional conflicts with
these had to be avoided as well.
3. Visual Considerations. The highways indicated
are main entrances to Decatur, so it was important
to avoid deterioration of the view. The generally
flat, open land contributes to long vistas.
4. Wildlife Refuges. The management of these ref-
uges naturally is disturbed by any potential en-
croachments on the areas. The management was
concerned with the reduction of habitat and the
possibility that birds might die from collisions
with lines.
Constraints were thus identified for practically the
entire study area. There was no neutral ground where a
transmission line could bebuilt.withoutsome conflict. The
only course left was to work out a location with full knowl-
edge of the situation and full participation of those
affected.
In this instance, avoiding encumbrances on the
developable land and maintaining an adequate distance
from the airport runways mandated a location near the
green belt. Once there, the location had to be reconciled, to
the extent possible, with the remaining constraints: visual
considerations and the wildlife refuges.
From. a visual design standpoint, the "edge" between
landscape features is often the most acceptable location
for a transmission line. In this case, the margin between
the open farmland and the wooded wildlife areas was the
strongest permanent edge. The irregular woods margin
could not be followed precisely. Instead, the route was set
back into the projecting wooded areas both to straighten
134
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Engineering and Migratory Birds
the lines and to gain a degree of concealment from the
highway vantage points. ·
By staying at the edges of the wildlife area and against
or among the trees as much as possible, instead of out in
the open, three things were accomplished: ( 1) The largest
possible parcels of wildlife refuge were left undisturbed,
(2) crossing a major waterfowl feeding area was avoided,
and (3) there was an attempt to keep the wood poles and
conductors from presenting unpredictable obstacles to
birds in flight.
The precise location oft he line was worked out in close,
on-the-ground cooperation with the U. S. Fish and Wild-
life Service and the Alabama Game and Fish Commis-
sion. These people then monitored the survey and con-
struction activities on the line as it was built. At the end of
the process the rights-of-way through the wildlife areas
were revegetated with wildlife food seed mixtures pre-
ferred by the U. S. Fish and Wildlife Service.
An attempt was made in the design of the transmis-
sion line to take into account the issue of bird collisions.
The single wood pole construction used for the General
Motors line permitted a greater degree of location flexi-
bility than steel tower construction. Wood pole lines pre-
sented a profile on the same order of height as the adja-
cent forest. By maintaining a low profile, by staying either
against or amidst the wooded areas, avoiding primary
feeding areas, and by designing the lines so the poles of
the parallel lines would be side by side as much as pos-
sible, the location participants believed the potential for
bird collisions with the transmission lines was minimized.
The use of wood poles also helped reduce the addi-
tional cost incurred by approximately 2 miles of extra line.
TRANSMISSION LINE DESIGN CONSTRAINTS*
The design of transmission lines is not inherently very
flexible. The physical characteristics of powerlines are
determined for the most part by engineering perfor-
*The examples used are generalized from TVA standards and are intended for
illustrative purposes only. They should not be construed as nationwide
engineering standards for transmission line design.
135
WAllen Miller
mance, reliability, public safety, and economics. This
leaves little opportunity for design compromises to reduce
bird collision potential. Electrical performance character-
istics determine wire sizes, spacing, configurations, and
number of circuits. These characteristics combine with
economics, topography, climate, strength of materials,
and many other factors to form the constraints which
guide transmission engineering. Let me briefly discuss
some of these constraints on line design and point out
areas where some flexibility exists.
Except in localized situations, our society is basically
dependent upon transmission lines to deliver electric
energy from remote generating sources. Transmission
facilities also tie adjacent electric power systems together
so that generating capacity at various locations can be
made available to the demand on any one system. For
technological and related economic reasons, almost all
such electric power in this country is transmitted on over-
head, three-phase, alternating current lines. Each one of
the phase conductors must be kept separate.
Electrical Insulation
Except at supporting tower locations, insulation for
these conductors is the air around them. The clearances
between overhead transmission lines and nearby objects
are set primarily to avoid the possibility of flashover. The
flashover distance-the distance an arc will jump and
short out the circuit-varies with the voltage rating of the
circuit but is well within the prescribed design distances.
Conductors on a TVA 500-kv transmission line, for
example, have a phase-to-tower clearance of 12 feet. That
is, the nearest grounded object (including the supporting
tower and shield wires) must be at least that far away from
the conductor. The individual phases must be spaced at
least 30 feet apart.
Lightning Protection
Lightning storm activity in most parts of the country
presents a real hazard to powerline reliability through
direct lightning strikes which can cause power outages by
flashing over insulators. In some cases lightning can seri-
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Engineering and Migratory Birds
ously damage insulators and/or sections of wire. To
provide protection against lightning, a smaller shield wire
is placed above the phase conductors to intercept the
strikes. This wire (or wires) in effect provides a "tent" of
protection for the line. This electrical shadow concept is
considered in most cases to extend protection at an angle
of 30 degrees from vertical. The coverage in relation to the
conductors and other surrounding influences determines
the number and placement of these shield wires .
Wind Pressure Effects
Wind pressure can cause conductors to swing. In the
free spans between towers and under some wind condi-
tions, the possibility exists that individual conductors will
swing "out of phase," so to speak, and move toward each
other. Therefore, the conductors have to be spaced far
enough apart at the towers to control the unrestrained
midspan phase-to-phase distance. For a 500-kv power-
line with horizontally spaced conductors restrained at
each structure, the distance from one phase to the next is
30 feet. Side swing also has a direct bearing on the width
of rights-of-way and on the separation between parallel
power lines.
Conductor Height Relative to Ground
The height of a conductor at any given location depends
upon-(1) minimum safety codes based on the flashover dis-
tance for a partic':llar operating voltage, (2) topography
under the line and objects that can intrude into the free
space, (3) climatic factors and power flows that influence
conductor sag, (4) electric field effects, and (5) spacing
between towers along the transmission line.
Conductor heights above ground are set primarily by
the electrical flashover distance in air which varies with
the line operating voltage level. This flashover distance
must beset liberallybecauseofthe manychangesthatcan
occur for a variety of reasons in the free airspace. Air
pressure, temperature, humidity, and airborne particles
can alter the insulating value of air. People, animals, and
mobile objects frequently occupy space under the line.
Trees and fast growing shrubs can, in a short period, sig-
nificantly reduce conductor clearances.
137
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Electrostatic fields, which are most noticeable in the
extra-high voltage range, introduce another design
parameter to be considered in selecting minimum con-
ductor heights. By maintaining adequate conductor
heights, the ground level strength of these fields can be
controlled to avoid excessive induced voltages, currents,
or other undesirable effects.
Conductor heights are not uniform along the length of a
line. Conductors, supported between towers, sag under
their own weight along catenary curves. Naturally, in hot
weather or when conductor temperatures are increased
by heat from resistance, the conductors will sag even
lower than normal. Conversely, under low ambient
temperatures the conductors will stretch tighter and
higher. All points along these catenary curves must main-
tain at least the regulated minimum height regardless of
operating temperatures or topography extremes.
Structure Spacing
Although structure spacing is by no means a random
process, it does represent one of the more flexible areas of
transmission engineering. Tower spacing is heavily
dependent on topography with the design attempt made to
spot towers along the rights-of-way where the greatest
design and cost advantages can be realized. The optimum
tower locations, though, often must be compromised to
avoid or minimize land use conflicts. A variety of spacing
and structure height combinations can be used to main-
tain minimum ground clearances. A great many closely
spaced, low structures can accomplish essentially the
same task as fewer tall structures with long spans.
The types of structures used for a line also influence
the spacing of structures. Shorter spans in the range of
400 feet to 600 feet are characteristic of wood pole
construction, while spans may range from 700 feet to
1400 feet for steel construction. The height and strength
limitations on wood structures are the basic reasons for
their shorter span capabilities.
138
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Engineering and Migratory Birds
Structure Strength
The reliability of transmission support structures is a
vital link in the reliability of the transmission system.
Transmission structures must be able to withstand
tremendous forces. They must bear the weight and
stabilize the placement of the conductors, insulator
strings, and groundwires not only under normal circum-
stances but under the most extreme conditions predict-
. able for the location. Ice and wind loads on the conductors
and on the towers themselves can more than double
normal loads.
Because of the side loads on structures at transmission
line angle points, the support structures must be much
stronger (and more expensive) than the straight-line "tan-
gent towers." Multicircuit transmission towers have
much greater loads to support than single-circuit towers.
Although transmission lines are built so that loads are
normally static, the towers are designed so that even if one
conductor were to break, the dynamic forces resulting will
not destroy the tower or the remaining conductors.
Structure Selection
Within these parameters there is enough design lati-
tude to allow many different tower styles and configura-
tions. The variety of aesthetic structures available attests
to that. Not all ofthetower designs available, however, are
suitable for general use in a transmission system. Many of
the aesthetic structures are limited in their loading
capacities so that their potential usefulness is reduced.
Other practical, economic, and environmental factors
must also be considered in selecting structure types.
Because of the numberoftowers used, thecostofeach
must be kept as low as possible. It must also be possible to
construct towers in the nearly impossible places trans-
mission lines sometimes must cross. The traditional self-
supporting, laced-steel structures meet these require-
ments. They provide the flexibility in design to assemble a
very strong structure from lightweight, relatively inex-
pensive parts. The self-supporting feature eliminates the
additional encumbrance ofthe right-of-way which a guyed
139
W. Allen Miller
structure would cause. In construction, these lightweight
parts provide a bonus in reduced impacts and costs of
hauling heavy structures over the rights-of-way. Except at
sharp angles (over 20 degrees), these towers normally do
not require concrete foundations-a major cost and con-
struction impact savings.
CONCLUSION
The purpose of this discussion of transmission engi-
neering is to identify the reasonable-and unrea-
sonable-avenues of pursuit for attempts to adapt trans-
mission lines to reduce or avoid bird collisions. These
areas of flexibility may be summarized briefly:
1. Attempts can be made to identify significant prob-
lem areas in advance so they can be avoided to
the extent possible through sensitive route selec-
tion.
2. Some transmission line design flexibility exists,
in many cases, in the choice of support structure
heights and spacing.
3. There is a degree of latitude in the choice of sup-
port structure materials and configurations.
It bears emphasizing that these areas of flexibility do
not indicate randomness in transmission engineering.
These areas still are bounded by strict engineering con-
straints and guided by economic responsibilities.
Although bird collisions with transmission lines have
not become a significant issue in the TVA region, it is
recognized that some bird collisions occur. In study areas
where line locations might raise the likelihood of bird
mortalities-whether through habitat alteration or colli-
sion potential-then the transmission line engineering
processes attempt to take this into account and work to
minimize damaging effects. In the near absence of
research-influenced and cost-effective design measures
to reduce bird collisions, TVA's efforts to mitigate colli-
sion impacts currently rely heavily on sensitive route
selection.
140
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ACKNOWLEDGMENT
Support from the personnel of the Division of Trans-
mission Planning and Engineering, Tennessee Valley
Authority, is gratefully acknowledged.
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Routing Transmission
Lines Through
Water Bird Habitat
in California
Edward W. Colson and Ellen H. Yeoman
Pacific Gas and Electric Company
Pacific Gas and Electric Company (PG and E) first
became involved in bird/powerline interactions in 1970.
At that time, concern was raised about the ecological
impact of electric power transmission lines and their
supporting steel towers on wildlife within the South San
Francisco Bay of California. Mr. Philip Arend of Wildlife
Associates, Inc., was consulted to evaluate the effects of
existing powerlines in the bay and to offer his profes-
sional opinion of the impacts these facilities pose for wild-
life. (Mr. Arend, formerly a waterfowl biologist with the
California Department of Fish and Game, has over 40
years' experience working with waterfowl and marsh
management.) His report was based on a comprehensive
literature review, interviews with numerous wildlife
refuge managers and other field workers, and personal
observations. Mr. Arend concluded, "Electric power trans-
mission lines mounted on steel towers cause very minor
avian loss, and their adverse ecological impact on avian
populations is negligible." Mr. Arend cited several
instances of bird mortality in water bird habitat mostly
attrjbuted to small diameter distribution lines, not high-
143
Edward W. Colson, Ellen H. Yeoman
voltage large diameter transmission lines. In most
reported cases, adverse weather or human disturbance
may have contributed to the mortality incident.
Since 1970, PG and E has prepared many environ-
mental impact reports, and discussions of bird/powerline
interactions are included as appropriate. Specific studies
to determine the scope of bird/powerline interactions in
northern California have not been conducted because our
company was not convinced bird/powerline interactions
were significant or because most projects did not enter
water bird concentration areas.
Recently, PG and E has considered major transmission
line projects through water bird habitat in three separate
areas: the South San Francisco Bay area, Sacramento Val-
ley, and the San Joaquin Valley of California. These areas
all contain important waterfowl wintering areas within the
Pacific Flyway. According to the U.S. Fish and Wildlife
Service, 60 percent of the migratory waterfowl on the
Pacific Flyway(approximately4 million ducks and 700,000
geese) winter in California. Large numbers of shorebirds
also winter in the state. Concern for bird/powerline inter-
actions has been raised locally by the California Depart-
ment of Fish and Game, the U.S. Fish and Wildlife Ser-
vice, the California Energy Resources Conservation and
Development Commission, and various public interest
groups. I will briefly summarize these project concerns.
STANISLAUS NUCLEAR POWER PLANT PROJECT
This project involves three possible power plant sites*
and several related alternative 500-kv transmission line
corridors within California's San Joaquin Valley. Impor-
tant water bird habitat exists in many areas of the valley,
and it is virtually impossible to avoid crossing wetland
habitat with all transmission line corridors. While one
corridor was adjusted to avoid the Kesterson National
*According to California Energy Resources.Conservation and Development
Commission (ERCDC), utility companies are required to submit development
plans on a minimum ofthree proposed power plant sites. The ERCDC-through a
36-month process of reports, workshops, and hearings-may issue a decision to
construct on one site and one (or more) land banked alternative.
144
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Routing Lines Through Bird Habitat in California
Wildlife Refuge, another 4-mile-wide corridor incorpor-
ates part ofthe Grasslands Water District. This area, in pri-
vate ownership, receives federal assistance for maintain-
ing wintering water bird habitat. The Grasslands Water
District and California Department of Fish and Game
oppose transmission lines through the area because they
believe habitat loss will occur due to the presence oftrans-
mission lines. They suggest that direct habitat losses will
occur when birds avoid habitat near newly constructed
powerlines, and a decrease in hunter experience will
result since birds may flare over lines beyond shooting
range. A reduction in hunter bag would reduce revenues
and could force landowners to alter their land manage-
ment practices and possibly convert the wetlands to other
uses.
SAN FRANCISCO BAY AREA
COMBINED CYCLE PROJECT
[ ___ _ ________ __ _ This project incl~dJ.s-f?ur possibl~ p?we~ plant ~ites
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within the vicinity of San Francisco Bay. One of the pro-
posed sites, North San Jose, includes a perferred alterna-
tive transmission line route adjacent to the South San
Francisco Bay National Wildlife Refuge. The refuge serves
an estimated 360,000 wintering waterfowl and 740,0C'Q
shorebirds. In addition, there are numerous existing trans-
mission lines crossing the bay in all directions. Although
PG and E proposed an alternative corridor adjacent to an
existing transmission line outside the refuge boundary,
the U.S. Fish and Wildlife Service and the California
Energy Resources Conservation and Development Com-
mission have recommended additional studies of water
bird flight patterns and undergrounding alternatives
before a final transmission line corridor is selected.
COAL POWER PLANTS
This project consists of studies of four possible power
plant sites and several alternative 500-kv transmission
line corridors in the Sacramento Valley. Several ofthe pro-
145
Edward W Colson, Ellen H. Yeoman
posed corridors traverse water bird habitat, including
freshwater marsh and rice fields. The Sacramento Valley
supports an estimated 2 to 3 million wintering waterfowl
and thousands of shorebirds. The U. S. Fish and Wildlife
Service has expressed concern that bird/powerline inter-
actions, similar to what Dr. Willard has described for the
Klamath Basin in the keynote address, are possible. The
presence of existing powerlines, dense tule fog, and high
concentrations of water birds provide conditions for pos-
sible bird/powerline interaction studies.
I have only briefly discussed these three examples of
bird/powerline interaction concerns expressed in these
projects. It is important to point out that the projects differ
consider ably.
TRANSMISSION LINE ROUTING PROCEDURE
PG and E has developed a sound transmission line
routing procedure that addresses engineering, economic,
and environmental concerns. The possibility of bird/pow-
arline interactions is included in all planned transmission
line projects. The first step in the routing process is to
locate a study area, usually encompassing several poten-
tial power plant sites and desired alternative power
delivery points. The next step is to select alternative
straight-line corridors (usually 4 miles wide) between the
power plant sites and the designated delivery points. All
existing transmission line corridors are mapped and
examined, and, whenever possible, proposed corridors are
modified to parallel existing routes. A regional study is
conducted to identify major constraints to transmission
line development. Environmental considerations at this
phase of the process include wildlife refuges, national and
state parks, natural areas, and other officially dedicated
lands that may be affected by the presence of transmis-
sion lines. Corridors are adjusted, where possible, to avoid
these designated areas. Adjustments based on continu-
ing economic and engineering studies and land use may
also lead to changes in the corridors. Each corridor must
contain at least one feasible trcmsmission line route.
The next step in the routing process is to choose poten-
146
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Routing Lines Through Bird Habitat in California
tial transmission line routes within the 4-mile-wide corri-
dors. Here, specific resource elements that could be
adversely impacted by transmission line development are
identified and, in most cases, avoided. Examples include
heron rookeries, eagle nests, and rare/endangered plant
locations. Eventually, an acceptable transmission line
route is chosen through the corridor.
The ecological studies for transmission line routing
involve literature reviews, agency and public interest
group input, field studies, and report preparation. Studies
on large projects may take from 1 to 3 years to complete.
Routing transmission lines in California, as in many other
parts of the nation, is a difficult and complex task. Many
issues and concerns develop regardless of the process
used to locate a powerline. Within the PG and E service
area, the concern with bird/powerline interactions is
another factor that is evaluated for all newpowerlinecon-
struction projects.
SUMMARY
The concern that transmission lines may pose a threat
to some avian species has been raised periodically in Cali-
fornia since 1970. However, little data existed until
recently to indicate that bird/powerline interactions were
worthy of specific study. The utility industry has spent mil-
lions of dollars in research to address such concerns as
thermal effects on aquatic life, cooling tower drift effects,
stack emission effects, noise effects, and electromag-
netic effects; and, until recently, the concern with
bird/powerline interactions simply was not being
addressed. Even now, with an estimated 100,000 circuit
miles of transmission lines located in all representative
habitats across the nation and with millions of resident
and migratory birds, incidents of bird losses have seldom
been reported.
The study of bird/powerline interactions is warranted
to place these interactions in perspective. This will require
sound research, time, and money. To explore the possible
scope of this concern, we will be seeking information on
collision potential, noise effects, electromagnetic effects,
and avoidance of habitat.
147
Edward W Colson, Ellen H. Yeoman
A -cooperative research approach, with industry and
the agencies working together to develop a predictive
model to help us avoid areas of potential significant impact
and possiply to predict the consequences of locating a
powerline in a given area, should be our goal. I believe the
industry is now willing to accept this opportunity and
challenge.
148
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The Klamath
Basin Gase
Ira D. Luman
Bureau of Land Management
Portland, Oregon
BACKGROUND AND HISTORY*
Pacific Power & Light Company is in the process of con-
structing generating facilities in Wyoming to utilize its
strippable, low-sulfur coal in that state. These facilities,
Jim Bridger and Wyodak, together with existing generat-
ing facilities would provide electric generation in excess of
Pacific Power's Wyoming load requirements for the
immediate future.
To utilize the large blocks of excess Wyoming power,
Pacific Power proposes to transmit it to load centers in the
Pacific Northwest, and southwestern Oregon in partic-
ular. Since Pacific Power has insufficient transmission
capacity to transmit this power from Wyoming to the
Northwest, it proposes to construct a new 500-kv power-
line between the Midpoint, Idaho, substation and a pro-
posed substation near Medford, Oregon. To implement
this proposal, Pacific Power fled two applications with the
*All data presented here is either directly quoted or summarized from the
report, "Final Environmental Statement. Pacific Power & Light Company,
Proposed 500 KV Powerline, Midpoint, Idaho, to Medford, Oregon," by U.S.
Department of the Interior, Bureau of Land Management.
149
Ira D. Luman
Bureau of Land Management, U.S. Department of the
Interior, for a 175-foot-wide right-of-way between Mid-
point, Idaho, and Medford, Oregon, a distance of approxi-
mately 480 miles (Figure 1 ).
According to PaCific Power, the proposed transmis-
sion line will serve the following purposes:
Figure 1. Proposed powerline route, Midpoint to Medford.
150
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1. Provide a means of transferring surplus electrical
energy from Wyoming coal-fired thermal plants
to load centers in the Pacific Northwest
2. Provide a direct means of supplying power to
meet thee nergy growth needs of southern Oregon
3. Be available for backup transmission capacity from
the Pacific Northwest to the Rocky Mountain area
in emergency situations
4. Contribute to the reliability of the interconnected
transmission grid in the Pacific Northwest
The proposed route passes over several areas
important to waterfowl for migration, resting, breeding,
feeding, and wintering. Some examples along the route
follow (see Figure 2).
The Bruneau Valley and adjacent Strike Reservoir in
Idaho are used by thousands of waterfowl. Major water-
fowl concentrations occur along the Snake and Bruneau
Rivers and Klamath and Warr.ar Valley Lakes. These
waters serve as habitat for resident species and provide
food and resting areas for the many migrants moving north
and south through the area east of the Cascade Moun-
tains.
The Warner Lakes in Warner Valley are a major nesting
and feeding area in the Pacific Flyway and undergo the
greatest seasonal bird use of any area along the proposed
Midpoint to Malin right-of-way. This area is also an
important rookery for herons and cormorants. Some
200,000 migrating birds are believed to pass through the
Warner Valley area annually.
Pelican Lake and Crump Lake, just south of the area
that would be crossed by the proposed right-of-way,
contain one of the two white pelican rookeries in Oregon.
The valley is an important migration flyway for ducks,
geese, swans, sandhill cranes, and many other waterfowl
and marsh birds.
South of Klamath Falls, Oregon, the proposed right-of-
way would cross the Klamath Basin, site of one of the
world's greatest waterfowl concentrations. The combina-
tion of proximity to open water, marshlands, grainfields,
and federal and state refuges makes the basin a water-
fowl habitat that is unexcelled. The route would skirt part
151
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of the Klamath Basin National Wildlife Refuge (see Figure
3).
These, and adjacent farmlands, are part of an
extremely productive waterfowl area and flyway route.
The refuges list over 180 species of birds nesting in the
basin. All the common dabbling and diving ducks are
abundant, with pintails predominating. Geese include
cackling, white-fronted, snow, and Canada geese. The
Ross's goose, smallest of all North American geese,
passes through the Klamath Basin on its annual migra-
tion. According to the U.S. Fish & Wildlife Service, this
flight represents the world population of Ross's geese.
It is estimated that over 5 million waterfowl pass
through the Klamath Basin annually. In addition, an
estimated 4,000 grebes, 1 ,000 white pelicans, 800
cormorants, 1,000 gulls, and 4,000 terns migrate through
this area.
A unique phenomenon in the Klamath Basin is the
mass waterfowl feeding flights. A waterfowl feeding flight
can be defined as one which is local in nature, relatively
low in altitude, and pursued by waterfowl for the purpose
of ingesting food. A feeding flight originates at a resting
area and terminates at a feeding area and vice versa.
Within the Klamath Basin, by far the largest and most
important feeding flight is the one that at least once in
each 24-hour period traverses the flight corridor between
the Lower Klamath Wildlife Refuge portion (almost all of
which is located in California) of the Klamath Basin
Nation~l Wildlife Refuges and the agricultural grainfields
which lie in southern Oregon, some 5 to 7 miles north of
the Lower Klamath Refuge. This feeding flight is referred
to as the "Lower Klamath feeding flight." The bulk of this
flight originates in the Lower Klamath Wildlife Refuge (the
resting area) and terminates in the grainfields to the north
(the feeding area) to the south of Midland and north of
Township Road, principally in the area known as Tulana
Farms. A return flight to the resting area (the Lower
Klamath Wildlife Refuge) is usually made within 12 hours
of the initial flight.
According to Tom Roster, an instructor at the Oregon
Technical Institute and shotgun ballistician who has
153
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-· LAMATH CO. I*-~--'--I-' > o).,_, -
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studied the local feeding flights extensively, the Lower
Klamath feeding flight numbers from a minimum of
30,000 waterfowl to a maximum of 800,000 waterfowl.
These birds (30,000 to 800,000) travel the feeding flight
route at least once each day. (This feeding flight phe-
nomenon should not be confused with the reference to
over 5 million waterfowl that pass through the Klamath
Basin at the peak of each fall migration.)
The area is heavily hunted. The Oregon Department of
Fish & Wildlife estimates more than 83,000ducks, geese,
and coots were harvested in the Klamath area in 1973.
Several private gun clubs are located near the Worden
area. The Oregon Wildlife Commission operates the
Klamath Wildlife Management Area north of Worden for
waterfowl and upland game use. South of Worden lie
three Fish & Wildlife Service Klamath Basin National
Wildlife Refuges. These refuges contain approximately
116,400 acres along both sides of the California-Oregon
line. The Lower Klamath Refuge lies 1 mile south of the
proposed right-of-way. The area is mainly flat farmland
with no natural obstruction to waterfowl flights. Heavy
fogs often prevail during the migration season.
ADVERSE IMPACTS TO WILDLIFE
It is believed that the construction, operation, and
maintenance of Pacific Power's proposed Midpoint to
Medford right-of-way and 500-kv transmission facilities
would cause the loss of bird life through collision with
lines and towers. The design of the proposed powerline is
such that it could result in bird losses of considerable
importance over the life of the project from collision with
the transmission facilities. The towers, conductors, and
shield or ground wires would impose serious barriers to
birds during migrating, feeding, and nuptial flights and
would kill or cripple birds colliding with them.
Nocturnal avian migrants and local feeding and nesting
populations are especiallypronetocollidewith man-made
objects. Magnitude of losses would depend on tower
height, visibility, bird density, and flight patterns. Most
birds normally migrate at a height that clears most man-
155
Ira D. Luman
made obstacles, but when blinded or confused, losses
could occur. This subject is controversial and needs
further study. Arend (1970), in a report for the Pacific Gas
& Electric Company, states that "electric power transmis-
sion lines mounted on steel towers cause a very minor
avian loss and that the adverse ecological impact on avian
populations is negligible." The Fish & Wildlife Service,
however, does not accept this as a blanket conclusion and
has indicated that major losses of migratory birds would
likely occur in areas of intensive use and low-level flights,
such as in the Klamath Basin and Warner Valley. A litera-
ture review shows that much of the data concerning colli-
sions is based on migrating passerines striking TV
antennas and tall lighting structures at airports. Most of
these towers are above the height of Pacific Power's pro-
posed 500-kv lines and towers. It is known, however, that
during periods of storm and poor visibility, resident and
migrating birds decrease elevation, become confused, and
.tend to strike lower structures. Also, waterfowl feeding
flights are usually much lower to the ground, making the
probability of collisions with powerlines much greater
than for migrating birds (Roster 1976, USFWS 1976).
The following are examples of bird losses from
collisions:
156
1. An estimated 50,000 birds lost through collision
with a ceilometer at Warner Robins Air Force Base
in Georgia. These birds were all passerines (John-
ston and Haines 1957).
2. Thirty thousand birds killed by a TV tower and guy
wires at Eau Claire, Wisconsin; 15,000 killed in
one night, nearly all passerines. This was a 1 ,000-
foot tower (Kemper 1964).
3. Twenty-one mute swans killed by impact and elec-
trocution by an overhead powerline above a reser-
voir in England. This was 30 percent of the total
flock (Harrison 1963).
4. One hundred night migrants killed at Oak Ridge,
Tennessee. An airport ceilometer contributed to
most of the passerine losses (Johnston and Haines
1957).
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The Klamath Basin Case
Twenty-three Franklin gulls and 20 blue-winged
teal killedbypowerlines. Dabbling ducks, with mal-
lards predominating, appear to be most vulnerable
to wire collisions (Krapu 1973). Seven hundred and
sixty passerines killed at the Omega Navigation
Tower, La Moure, North Dakota (USDI, 1974).
Anderson (1978) discusses losses of waterfowl by
collisions with powerlines across a 2, 155-acre lake
near a large power plant in Indiana. An estimated
300 waterfowl (out of 1 00,000) were killed during
a 4-month period. The study concludes that the
mortality was relatively minor in terms of the total
population, since the vast majority of birds had
flight patterns that did not bring them near the
powerline.
7. Scott, Roberts, and Cadbury (1972) state that in
England powerlines of 400 kv, 275 kv, 132 kv
"sited near estuaries, river valleys or between
bodies of water provide a particular hazard when
they lie across flight paths used by waterfowl, wad-
ers, gulls, or other water birds between feeding anCf
roosting area." Their study accounted for a known
loss of 1,285 migratory birds, with 6,000 (includ-
ing passerines, gulls, rails, and ducks) estimated
killed over a 6-year interval at Dungeness, Kent.
The Fish & Wildlife se·rvice states that
"the greatest threat occurs when large numbers of birds
concentrate in an area for resting, feeding, or nesting pur-
poses. These birds stay for a period of time ranging from
a few days to 3 or 4 months. Soon after arriving at such
an area the birds develop a series of flight patterns that
are not similar to migration flights. These movements are
usually most pronounced between sunset and sunrise
when lighting and visibility are poor. Another character-
istic of these flights is the low elevation at which they
occur, especially within or adjacent to the feeding and
resting sites. It is during these local flights that collisions
are most likely to occur rather than during migration
flights, which often cover hundreds of mites nonstop at
high elevations. The problem is increased by inclement
weather conditions such as local fog or snowstorms which
157
-~------------------t "
Ira D. Luman
restrict visibility and often cause the birds to fly at low
elevations" (USFWS 1976).
While the anticipated loss of waterfowl and other
migratory birds on the proposed line is speculative, the
Fish & Wildlife Service feels strongly that major losses
would probably occur. Intensive waterfowl flights in the
Hagerman area, especially during migrations down the
Snake River, would be subjected to possible losses due to
collisions with the powerlines and towers. Birds would be
most vulnerable during periods of low visibility and in-
clement weather. Migrating birds, including passerines
and waterfowl, would be lost through collisions. For ex-
ample, if 0.05 percent of over 2 million waterfowl migrat-
ing through Idaho across the proposed route were lost, it
would amount to 10,000 birds; however, it is not possible
to quantify numbers or species.
Waterfowl concentrations are found at the Bruneau
River crossing and adjacent C. J. Strike Reservoir, during
both feeding activities and migration. The proposed right-
of-way crossing at the Bruneau River would result in
losses similar to those anticipated at Hagerman. Other
migrating birds, including such passerines as mourning
doves, are vulnerable where an unknown number of
flights would cross the proposed right-of-way. Con-
centrations of many other birds are found along the Snake
River parallel to the proposed right-of-way from Hager-
man to the Bruneau River, a distance of nearly 60 miles,
increasing the likelihood of powerline collisions.
A major wildlife concentration occurs at Warner
Valley. It is one of the most vulnerable areas along the pro-
posed Midpoint to Malin right-of-way. More than 10,000
waterfowl use the Warner Lakes as a breeding-feeding
area. An unknown, but substantial, number of migrants-
including other ducks, geese, coots, shorebirds, terns,
cranes, pelicans, cormorants, passerines, and raptors -
pass through this area.l n addition, the area is heavily used
by waterfowl, pelicans, and other migrants for feeding.
Annual counts have shown nearly 200,000 birds in the
area.
The greatest potential hazard to wildlife would come
from placement of the powerli ne from the west edge of the
158
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The Klamath Basin Case
Klamath Hills to the Worden area on Highway 97 - a
distance of approximately 7 miles. This part of the pro-
posed right-of-way would cross the major portion of the
migration route for nearly 5 million waterfowl and
thousands of other migratory birds that move through the
Klamath Basin. In addition, an unknown number of daily
feeding flights of resident waterfowl would pass across
the proposed right-of-way. There are no natural obstruc-
tions in this 7-mile area to screen the proposed transmis-
sion line or make waterfowl rise to higher flight eleva-
tions. While losses of waterfowl and other migrants are
speculative, the references indicate that losses will occur.
They could also be very high (USF&WS 1976).
Since the area is also important to breeding birds, there
would be losses of ducks during erratic nuptial flights.
During periods of poor visibility, such as at night when
many migrations and feeding flights occur, the birds would
have a barrier of 11 conducting and ground wires to fly
past along a 14-mile segment of the proposed right-of-
way. Heavy fogs, storms, and wind cause elevation varia-
tions in feeding flights in that area, increasing the possi-
bility of collision.
Besides the ducks, geese, and swans using this area,
gulls and terns, grebes, and white pelicans counted annu-
ally by the Fish & Wildlife Service as well as cranes,
herons, shorebirds, and passerine species would have to
cross this aerial barrier. Based on losses in other areas,
losses of thousands of birds could be anticipated in the
Klamath Basin.
In his testimony before the Public Utilities Commis-
sion hearings officer, Roster (1976) described mass
feeding flights of nearly 800,000 birds in the Klamath
Basin. Since these low elevation flights between marsh-
lands and grainfields occur at dawn and dusk when visi-
bility is poor, he believes the proposed powerline would
present an especially dangerous obstacle.
If the birds should change their flight routes to avoid
collisions with the powerline, the result could be an
adverse economic and recreational impact on Klamath
Basin residents, especially if the birds move across the
state line into California (Roster 1976). The U.S. Fish &
159
Ira D. Luman
~~--------------~----~-------L
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Wildlife Service indicates that landowners in Illinois were
awarded compensation of up to $100,000 for decreased
hunting opportunity attributed to a powerline. Martinka
(1974) states that duck shooting declined by two-thirds
after a powerline crossed a Wisconsin hunting area and
that Canada geese in normal flight would notflyunderthe
line.
As cited above, loss of migrant birds is speculative, and
opinions about the probable magnitude and significance of
bird kills vary greatly. Power company representatives
indicate that minor losses will occur. On the other hand,
the Fish & Wildlife Service has indicated that major losses
will probably occur.
MITIGATIONS
Of the mitigations cited for wildlife in Chapter IV of the
powerline impact statement by the Bureau of Land
Management (USDI1976), only one pertained indirectly to
collisions of waterfowl with conducting lines and towers.
It stated that towers should not be placed in open expanses
of water and marshland, particularly those utilized as
flight lanes, nesting, rearing, or feeding sites by migrating
waterfowl and other birds. It is hoped that this action
would mitigate, to an unknown degree, wildlife habitat
destruction and wildlife displacement, and possibly colli-
sion with the towers.
Overall, it was felt that collisions of waterfowl and pas-
serines with towers, conductors, and shield wires were an
unavoidable wildlife impact that could not be mitigated.
This is especially true at key migration and feeding sites
such as the Snake and Bruneau Rivers, Warner Valley,
and the Klamath Basin.
Long-term impacts are feared, especially if the power-
line route selected becomes a transmission corridor
through waterfowl and other migrating bird concentra-
tion areas. Adverse effects in migration and feeding
patterns and direct losses by collisions with towers, con-
ductors, and shield wires would be anticipated. Annual
losses would be expected to continue over the life of the
project, especially in the case of multiple lines or a power
corridor (see Figure 4).
160
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ALTERNATE ROUTES
In addition to the proposed route from Midpoint, Idaho,
to Malin, Oregon, four alternate routes have been studied,
some of which bypass the Bruneau River and Warner
Valley areas. These will not be discussed in detail. In every
case, however, all routes terminate at Malin, Oregon. In
the segment from Malin to Medford through the Klamath
Basin, it is very difficult to find an alternate route that
would effectively cross migration routes without adverse
impacts to the waterfowl flights through that area.
One alternate route (Route II) would parallel the pro-
posed route, passing slightly to the north, with the same
anticipated impacts as for the proposed route and
alternate route I. Alternate route Ill would begin at Malin,
then turn north almost to the city limits of Klamath Falls,
crossing the Klamath River east of the Weyerhauser saw-
mill, then heading west north of the proposed route. This
route would para lie I most of the flyway patterns except for
the one-half mile long crossing near Klamath Falls, where
it would again bisect major waterfowl flight patterns. It
would also cross Ross's geese feeding flights in the east
side of the Klamath Basin, and it would cross near the
Miller Island Wildlife Management Area (Oregon).
Alternate route IV would dip down into northern Cali-
fornia, going south and west of Fish & Wildlife's Lower
Klamath Refuge and close to some large private hunting
clubs. It would parallel Sheepy Ridge, which divides the
Lower Klamath Refuge from TuleLake Refuge and which
also constitutes an important hunting area. This refuge
area is heavily used by waterfowl, shorebirds, and other
migrants for feeding and nesting, and the alternate route
would be crossed by extensive feeding flights near Merrill.
Migration flights would probably be well above the power-
line since it would be under the crest of or through some
low hills on the south, southeast, and southwest sides of
the Lower Klamath Refuge (see Figure 5).
SUMMARY
The problem of waterfowl and other migrants colliding
with powerlines is well documented where feeder lines
162
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Proposed Route
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and other small conductors are concerned and where TV
towers, airport lights, etc., have caused heavy losses -
especially to passerines in bad weather. The problem is
not well documented where large diameter conductors,
bundled conductors, or large multiple lines are con-
cerned. Based on the literature, however, heavy losses to
waterfowl, cranes, pelicans, other shore and water birds,
as well as migrant passerines are anticipated in areas of
heavy bird concentration, such as in the Klamath Basin.
On November 21, 1977, the Secretary of the Interior
informed Pacific Power that the Department ofthe Interior
has determined that alternate route I, between Midpoint
and Malin, is clearly the preferred one, and Pacific Power
has indicated it will make application for that route.
Between Malin and Medford, the Secretary, recom-
mended alternate route Ill or to construct the project along
the proposed route, but he also indicated to mitigate the
impact by undergrounding through the critical area in the
Lower Klamath Basin.
REFERENCES
Anderson, W. L. 1978. Waterfowl collisions with power-
lines at a coal-fired power plant. Wildlife Society Bull. In
press.
Arend, P. H. 1970. The Ecological Impacts of
Transmission Lines on the Wildlife of San Francisco Bay.
Prepared for Pacific Gas & Electric Company.
Harrison, J. 1963. Heavy mortality of mute swans from
electrocution. Annual Report. The Waterfowl Trust, 1961
and 1962. 14:164.
Johnson, D. W., and Haines, T. P., 1957. Analysis of mass
bird mortality in October 1954. Auk 74:447-58.
Kemper, C. A. 1964. A tower for TV: 30,000 dead birds.
Audubon 66(2):86-90.
Krapu, G. L. 1973. Overhead Wires. A Common Cause of
Bird Mortality in North Dakota. U.S. Fish and Wildlife
Service, Jamestown, North Dakota.
164
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The Klamath Basin Case
Martinka, R. 1974. The new horizon. Montana Outdoors
July I August.
Scott, R. E.; Roberts, L. J.; and Cadbury, C. J. 1972. Bird
deaths from powerlines at Dungeness. British Birds
65(7):273-86.
U.S. Department of the Interior, Fish and Wildlife Service.
1973. Investigation of Bird Migration and Losses
Associated with the Omega Navigation Station, Lamoure,
North Dakota. Federal Aid Report, 1974.
U.S. Department of the Interior, Fish and Wildlife Service.
1976. Letter commenting on Draft Environmental Impact
Statement. Pacif1c Power Proposed 500-KV Powerline,
Midpoint. Idaho. to Medford, Oregon.
U.S. Department of the Interior, Bureau of Land
Management. 1976. Draft Environ'mental Impact State-
ment, Pacific Power Proposal 500-KV Powerline. Mid-
point, Idaho. io Medford. Oregon.
165
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Behavior
Working
Group
Summaries
The working group on behavior addressed the aspects
of bird behavior that would enhance bird strike prob-
abilities at power lines, and the group attempted to identify
those circumstances most closely associated with bird
collisions at powerlines. This was done whenever possible
according to bird species grouped into four general cate-
gories: ( 1) waterfowl, (2) shorebirds, (3) raptors, and (4)
small nongame birds.
We first considered the importance of weather condi-
tions in evaluating the risk of powerline collision for birds.
The weather conditions that influence visibility or detect-
ability of transmission lines were treated separately from
those influencing flight activity of a local movement nature
and of a migratory nature. The group generally agreed that
conditions of low visibility (very low ceiling of thick clouds
and precipitation) are the major weather conditions that
William L. Anderson, Frank Cassel (recorder}, Milton Friend, Sidney A. Gau-
threaux, Jr. (chairman}, GilbertS. Grant, Donald A. Hammer, Carl Korschgen,
Richard L. Morgan, Richard L. Plunkett, Kent Schreiber, Bob Welford.
167
--~-------~------~---------------~, -
Behavior
affect detectability of transmission lines. With regard to
detectability, the contrast of the wires or cables against a
background should be considered. Rendering lines more
conspicuous to birds could have potential problems, and
more work is needed in this area. Weather conditions that
enhance low-level local movements of birds and the
volume of these movements are basically the same as
those that decrease powerline detectability. Waterfowl in
general are quite active in such weather, particularly with
wind. Raptors may move and feed at lower altitudes during
low visibility conditions, and passerines are probably less
active in terms of flight activity. Very few quantitative
studies exist that address the influence of weather condi-
tions on the amount of local movement in bird species.
Most of the evidence is somewhat anecdotal.
With regard to spring and fall migration, we know the
weather conditions that contribute to massive move-
ments of birds (see Gauthreaux this proceedings). In
general, once migrants are aloft in large numbers and
weather conditions deteriorate to those of low ceiling and
visibility, bird strikes at powerlines increase. Also, when
favorable conditions for migration occur in the lowest
stratum above the ground (even under clear skies), the
number of collisions may be considerable (see Avery et al.
1977).
The time of day when collisions are most likely to occur
largely depends on the activity cycles of the species. At
night, powerline detectability is lower, so birds, such as
waterfowl and shorebirds, moving into feeding areas at
dark or after nightfall on full moon nights are particularly
susceptible. Early morning and late afternoon are usually
periods of elevated flight activity( e.g., roosting flights), but
some raptors are active only after sufficient thermal acti-
vity has developed late in the morning. With regard to
. migratory activity, Gauthreaux (this proceedings) has
summarized the hour-to-hour variation in the quantity of·
migration in species that migrate at night, during the day,
or both.
The time of year is also important in assessing the
probability of bird collisions with transmission lines.
Courtship activities involving flight displays enhance the
168
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Working Group Summaries
chances of a collision on a local scale. Similarly, the
accumulations of birds during winter at places of food con-
centration or in areas of open water (e.g., "cooling" ponds
near nuclear reactors during winter when other areas are
frozen over, see Anderson 1978) strongly increase the
chances of birds hitting transmission lines. The season-
ality of weather conditions at a locality must also be
included in this section, because low visibility weather
conditions may occur at a particular time of year at a
certain locality. It is rather obvious that seasonal migra-
tions will drastically a Iter the probabilities of bird strikes at
transmission lines on a month-to-month basis. The
periods of spring and fall migrations should be of partic-
ular concern.
The group considered next the special behavioral char-
acteristics of birds that would greatly increase their
chances of colliding with transmission lines. It would
appear that raptors actively pursuing prey in flight are
more vulnerable to a collision with transmission lines, but
factors such as size of bird, wing span, and maneuver-
ability (erratic or straight flight) should be considered. The
group agreed that when birds are pursuing prey, engaged
in courtship flights, defending a territory, or escaping from
a predator, they are particularly prone to collide with a
powerline, because they are preoccupied and are not very
alert to the hazards that transmission lines pose.
The altitude of flight is also an important behavioral
characteristic that contributes to the probability of a colli-
sion. For example, blue-winged teal are more vulnerable
to collision than mallards, for the latter usually fly higher.
Local movements of birds are usually at lower altitudes
than migratory movements. During hunting season water-
fowl fly higher, but they maybe startled from a lakeandfly
into powerlines. In migration birds fly at different altitudes
depending on their size, the time of day, and th,eirdestina-
tion (see Gauthreaux this proceedings). During the day,
some species usually fly over transmission lines (e.g.,
Canada geese, larger ducks, gulls), while others often fly
under the lines (e.g., many songbirds) unless on a migra-
tory flight. Another important aspect to be considered
relates to learning and habituation. Local birds are more
169
Behavior
likely to know the location and perhaps even the danger of
a particular transmission line, while transients will not be
so conditioned. Birds certainly are capable of learning
about the hazards associated with a transmission line.
Another important point discussed by the working group
concerned the closing rate and maneuverability of a
species. Intuitively, it appears that those species with
greater powers of maneuverability will have a reduced risk
of colliding with transmission lines. Flight speed, wing
loading, and other aerodynamic aspects of bird flight
should be examined in terms of the species that actually
hit transmission lines. Little can be said about the
differential risk of powerline collision in flocking and
nonflocking species, and more work is needed in this area.
The placement of transmission lines is important in
assessing the risk of collision. The vertical array of wires
should be minimized. If at all possible transmission lines
should be kept on a single horizontal level. Thicker lines
are more conspicuous, and the ground or static lines above
transmission lines should be made more conspicuous or
put at the level of the transmission lines, if possible. Trans-
mission lines should be kept below the level of the forest
canopy. Because forest birds have greater maneuver-
ability in flight and fly slower than those species flying
above the level of the forest canopy (e.g., ducks, raptors,
doves), the former are less likely to sustain heavy power-
line strikes. Powerlines should not under any circum-
stances be positioned just above the level of the forest
canopy. Self-supporting towers present less of a hazard to
birds than towers supported by guylines. In particularly
hazardous areas, powerlines should be placed under-
ground. It should be pointed out that platforms and
perches on powerline towers have, under certain condi-
tions, proved beneficial to nesting raptors (see Gilmer and
Wiehe 1 977).
Construction of powerlines in critical habitats where
local or migratory movements are very predictable should
be avoided. Such areas might include wildlife or water-
fowl refuges with tremendous concentrations of bird life,
shorelines, mudflats, or entrances to estuaries. Modifica-
tion of habitat should be considered with caution.
170
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Although fast growing tree rows may render powerlines
less conspicuous and effectively block the flow of low
flying birds, the ultimate "benefit" of such a practice
should be carefully evaluated. The working group
discussed a specific problem of powerline location in the
Phepp's Bend area 100 miles northeast of Oak Ridge, Ten-
nessee, where a powerline will cross a ridge. In this case
the potential risk to migrating raptors along the ridge is of
particular concern. Once again, it was stressed that the
powerline should be kept below the level of the canopy as
much as possible to minimize the risk .
Finally the group recommended that the terms cor-
ridor and row be carefully distinguished. Perhaps a term
such as impact area that is not necessarily as large as a
corridor or as small as a row should be used in addressing
habitat in the powerline area. The impact area would be
the area in which powerlines and towers have a be-
havioral or ecological effect.
The group was in general agreement that more care-
fully designed and quantitative studies are needed to fully
evaluate the overall impact of transmission lines on
various groups of birds, and that the deliberations of the
working group represent but a modest and somewhat
hesitant first step in that direction.
REFERENCES
Anderson, W. L. 1978. Waterfowl collisions with power
lines at a coal-fired power plant. Wildlife Soctety Bull. In
press.
Avery, M.; Springer, P. F., and Cassel, J. F. 1977. Weather
influences on nocturnal bird mortality at a North Dakota
tower. Wilson Bull. 89 (2) :291-99.
Gauthreaux, S. A., Jr. 1978. Migratory behavior and flight
patterns. This proceedings.
Gilmer, D. S., and Wiehe, J. M. 1977. Nesting by
ferruginous hawks and other raptors on high voltage
powerline towers. Prairie Nat. 9(1):1-10.
. 171
Habitat
Habitat
The habitat group considered and discussed four
general topics: (1) relationships between habitats and the
frequency of bird strikes, (2) use of this information in
siting transmission and distribution lines (we did not
discriminate between types of overhead lines), (3)
research needed, and (4) general procedures for selecting
the best routes for lines.
A list of more than 80 bird species that have been
recorded as killed by striking utility wires was distributed
(see Thompson this proceedings, Table 1 ). Approximately
50 percent of these species typically inhabit lakes and
marshes. (Species of prairie habitats and of seashore or
saltmarsh ranked second and third in this list.) Consider-
ing the preponderance of geese, ducks, pelicans, herons,
etc., in this mortality and recognizing the public interest in
these birds and their economic, political, and ecological
importance, we discussed primarily the importance of
marshes, ponds, and lakes in the bird strike problem.
The available data indicate that routing lines to avoid
wetlands is desirable, and that the location of these
habitats warrants special attention in any plan for power-
line siting. In particular the following must be noted:
1. Corridors between two bodies of water or marshes
should be avoided.
2. Corridors that intersect known flight paths
of waterfowl and similar species should be avoided.
To identify these flight paths, intensive studies are
needed, especially of flights of local populations
between feeding and resting areas or between feed-
ing and nesting areas such as heron rookeries.
3. Corridors across estuaries, because these may be
important routes for both local movements and
migrations, should be located only after investiga-
tion of bird movements at all seasons.
Michael L. Avery (recorder), Robert Berg, Bob L. Burkholder, Len J.
Cernohous, Edward Colson, Dale Fowler, J.A.R. Hamilton, Roger Kroodsma,
Jack M. Lee, Jr., Ira D. Luman, Ben Pinkowski, J. T. Tanner (chairman), William T.
Tucker, Jochen H. Wiese.
172
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Working Group Summaries
In addition to studies of flight paths in local areas,
several other subjects were proposed for needed research.
One subject was suggested by the steering committee: the
width of a zone on either side of a transmission line in
which birds are vulnerable. This is clearly a subject for
research. However, the vital question is how important to
local bird populations is mortality from wire strikes. Much
more data will be needed on the mortality rates of dif-
ferent species in different areas if resolution of the
problem is based on a cost-benefit analysis. We all
appreciate the difficulty of obtaining such data, yet at the
same time we believe better decisions would be made if
cost-benefit analysis could be used. We suggest, for
practical and political reasons, that studies of this nature
be initiated on waterfowl and later extended to other
species.
Another type of habitat was briefly considered: obvious
topographical features. Ornithologists, especially in
Europe, have studied the migrations of birds through
mountain passes and have found that large numbers of
many species migrate both day and night through these
passes, often at very low heights above the ground. There
appears to be no data on birds being killed by wire strikes at
these places, but mortality seems very possible. The group
suggests that studies might be made at ridges, mountain
gaps, and other topographical features that tend to
channel or concentrate flight paths.
As in almost all environmental problems, the essential
question is how can information of all sorts, including that
from wildlife biologists and ecologists, be best used to
influence decisions, in particular, to choose. We are here
concerned with the choice of a "best" route for a trans-
mission line. We urge that biological and ecological input
be introduced into powerline planning at the very earliest
stages. In addition to the previous discussion on the
habitats which should be identified for best routing,
certain other areas need to be excluded categorically:
national and state parks, national and state wildlife
refuges, wilderness areas, critical habitats for endangered
species of both plans and animals. By compiling an
inventory of the various habitat types and land uses in the
173
Mitigation
area under study and by categorizing them as to their use
and relative importance to man and to wild species,
decisionmakers should be able to balance the information
to arrive at a "good" decision.
Mentioned above are some of the particular points con-
cerning habitats and transmission lines which need to be
included in this inventory and classification. A conclusion
of the working group on. mitigation that bird losses might
be reduced by placing utility lines adjacent, and parallel, to
natural barriers suggests that the location of such barriers-
should also be included. We would suggest also that it
might be practical to computerize all this information to
provide a readily accessible data base with which the
desirability of various alternative routes could be
evaluated.
Mitigation
The working group on mitigation began its work by
examining the initial notion that powerlines can cause
significant adverse effects to waterfowl, raptors, shore-
birds, passerines, and threatened and endangered
species. The group did not reach a consensus on this, but it
did agree that local areas of potential conflict may occur in
any part of the nation and that the conflict in local areas
may have national interest. In other words, there is a
national problem with varying local manifestations. How-
ever, all transmission lines at potential routes throughout
the nation do nota priori cause conflict. The committee did
think each of the conflicts was important, but could not or
would not deal with "significance" or "nationalness." The
utility members tended to downplay the importance of the
conflicts. (It is not important to them.) For the conserva-
tionists and· wildlife biologists, the converse is true. (It
appears that a compromise statement serves no one.)
Possible conflict between powerlines and birds is of
Spencer Amend, Joe Binder, Richard C. Crawford, Ron Freeman (recorder),
W. Allen Miller, Dean Miller, LarryThompson(co-chairman), RichardS. Thorsell,
Howard Teasley, Roger Vorderstrasse, Keith H. Wietecki, Daniel E. Willard (co-
chairman).
174
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such importance that biologists should designate areas in
which powerline impact must be studied on a site-specific
basis. Because of the difficulty of this task, the geographic
areas that industry engineers believe will be soonest in
jeopardy should be studied first.
Specific Mitigation Practices
Using a nominal small group process, we developed a
list of 17 mitigation practices:
I. Methods that simply avoid bird concentration
areas in corridor selection
1. Siting
2.
3.
4.
Upgrading the existing system
Removing conductors
Not building
5. Creating load-center generation
II. Methods that adjust the right-of-way to reduce
conflict.
6. Following and being compatible with exist-
ing barriers
7. Scattering lines
8. Clustering lines
Ill. Methods that modify conductors and structures
to reduce the probability of collision
9. Diverting birds by modifying habitat and
creating alternate habitat
10. Placing lines underground
11. Increasing visibility
12. Changing conductor configuration
13. Creating shelter belts
14. Repelling birds with corona noise and preda-
1 tor and distress calls
15. Controlling human access
16. Changing the shape of towers
IV. Compensating for damage to bird populations
175
Mitigation
Each method was considered in terms of the following
questions:
1. Is this method effective in reducing bird strikes
and habitat destruction?
2. If it is effective only in special conditions, what
are they?
3. What costs are involved?
4. What disadvantages are there?
5. Are we· confident of the method? If not, what is
needed?
6. Is it feasible and worthy of further consideration?
Consistent with our initial remarks, we caution that
solutions must address specific target species. These
measures apply only in cases where potential collision
losses are great enough to warrant the mitigation
expense. We did not address ourselves to a method for
making these comparisons except to note that this
problem needs much work.
In contrast to the earlier emphasis on site-specific
planning, we believe that, in the area of physical altera-
tions to transmission facilities, generic solutions are desir-
able. However, they should be tested for effectiveness
against a reasonable variety of target species and specific
localities.
Avoiding Areas of Bird Concentrations
Obviously, if the powerline avoids birds, collisions will
be nonexistent. The conditions that make this option most
effective include a variety of considerations. Trans-
mission route planners need to know early in the planning
phase where the significant areas are located. Areas in
which there are high concentrations of birds and areas
which conflict with socially important species(e.g., Ross's
geese, limpkins, Kirtland's warblers) should be avoided.
We note that routing around these significant areas is
easier when there are few and localized concentrations
along the proposed route. There are many different and
often conflicting interests pressuring route selectors.
Along a proposed route in southwestern Minnesota, state
176
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and federal wildlife experts and sportsmen's groups argue
that this corridor should avoid potholes, sloughs, and
marshes that contain waterfowl. The marshes are sur-
rounded by wheat farms, and farmers do not want the
lines or towers either. This sort of competition from special
interest groups is not unusual, and routing decisions
require hard data on waterfowl concentration areas. Engi-
neers claim that each additional mile of transmission line
costs about $250,000, which is passed on to the rate
payer.
Avoiding wildlife concentrations is quite feasible, but it
is absolutely essential that they be positively and agres-
sively delineated, their locations mapped, and these maps
widely circulated. Other land uses compete and longer
lines cost somewhat more so line routing involves weighty
decisions. Because of the complexities and uncertainties
involved, utility planners were eager to discuss such
options as not building the line at all.
Where a suitable line and right-of-way exist most
environmental impacts can effectively be reduced. System
planners routinely consider this option, as well as the no-
build and load-center questions. No-build and load-center
generation (many small generating facilities located close
to users so virtually no lines are used) meet or guarantee
peak capability better than base loads.
Upgrading has long been used when it costs less than
new construction. However, upgrading sometimes costs
more, reduces system reliability, and aggravates existing
land-use conflicts. The no-build situation should properly
be called "not build this segment" for something else will
be done, at some cost, somewhere else. Load-center
generation may worsen local air quality and deplete the
supply of hydrocarbon fuels.
Adjusting the Right-of-Way To Reduce Collisions
Two kinds of options were considered in this category:
routing to follow natural barriers and the placement of
lines relative to each other.
Following Existing Natural Barriers. Generally, lines
placed next to objects that birds already avoid (for example,
along the bases of ridges or along highways) would reduce
177
Mitigation
the probability of collision. Placing lines within a forest
canopy presents both advantages and disadvantages.
With higher voltages, structures rise well about 100 feet.
A line protruding just above the canopy was thought to be
quite dangerous to some species that move swiftly above
the canopy. On the other hand, placing structures below
the top of the canopy would be a hazard for forest species.
In addition, the forest itself will be destroyed along the
route. Adverse aesthetic consequences may also result.
Anything that lengthens a route will increase the cost
and require more land. The latter aggravates the diffi-
culties inherent in the right-of-way acquisition process.
However, lengthening the route is entirely possible with
today's technology.
Line Placement in Relation to Other Lines. The group
discussed whether collisions can be reduced through
alternate line placement. Some suggested placing new
lines close to existing lines, making one big hazard rather
than two small ones. Others preferred placing a new line
some distance from the first to reduce the complexity and
solidity of the barrier. Observations were reported to
support both views. Either method is feasible, and addi-
tional expense is related only to I ine length. Higher voltage
conductors must have more ground clearance, and
systems of widely differing voltage are less compatible
than systems of the same voltage.
Modifying Conductors and Structures
The group examined the following eight specific
suggestions, many of which can be used on existing con-
ductors. All assume a fixed route.
1. Modifying habitat
2. Placing conductors underground
3. Increasing wire visibility
4. Changing wire configurations in space
5. Screening lines with trees
6. Removing the static wire
7. Repelling birds
8. Preventing distractions to birds
178
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Modifying Habitat. Theoretically, flight routes go from
one resource to another. The suggestion here is that when
the flight route and line route conflict, one of the attrac-
tive bird habitats can be moved to reduce the conflict. The
committee reported no evidence to support or deny the
usefulness of this suggestion. Members did, however,
have several reservations, and it is symptomatic of our
knowledge that some of the reservations conflict.
Several waterfowl biologists contended that birds fly
traditional patterns and changing them would be difficult.
Others noted that flight patterns change from year to year
in response to both changing winds and land-use
practices. Additional costs might arise from land acquisi-
tion or leasing. The suggestion contains no technical
limitations.
Placing Conductors Underground. Utility engineers
agreed that in situations with no great construction prob-
lems, such as shallow bedrock, distribution lines would
not be prohibitively expensive to put underground. How-
ever, they felt strongly that putting higher voltage ( 110 kv
and above) lines underground was still economically and
technically impossible. Buried lines are not reliable, and in
rural conditions they are difficult to maintain.
Burying lines disturbs the soil, although no compari-
son was made with soil disturbance caused by above-
ground structures. If cooling oil leaked, soil organisms
would be damaged.
Burying is feasible for distribution lines, but the costs
and advantages should be carefully compared with above-
ground systems.
Increasing Wire Visibility. There is no data to deter-
mine the effectiveness of various devices for increasing
the visibility of conductors and other structures, but the
costs are low and, in some cases, markers could be
helpful. These mitigations merit further investigation.
Some devices are summarized below:
1. Aircraft warning balls are already available; prob-
ably effective in clear, lighted conditions; and
cause no harm in low visibility conditions. How-
ever, they may be aesthetically displeasing to
humans.
179
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Mitigation
2. Lighting conductors is technically difficult, aes-
th~tically displeasing, and perhaps countereffec-
tive in poor visibility situations.
3. Reducing the size of, and brightly marking, the
static wire presents no technical difficulties or
change in new construction. However, these miti-
gations have unknown effectiveness in reducing
bird strikes. Because the static wire has been
implicated in many documented collisions, mark-
ing it might be helpful.
4. Coloring conductors is feasible and inexpensive.
It could decrease collisions and cause no harm.
Here, particularly, we find a conflict in regulatory
priorities. Conductors made more visible to birds
are also more visible to humans, and national ten-
dency recently has been to reduce the aesthetic
impact of conductors.
5. Strobe lights placed on towers appear to be inef-
fective and unsightly.
Changing Wire Configurations in Space. The
evidence now available does not indicate whether any
certain line height or shape decreases collisions.
Bird/wire collisions might decrease if parallel conductors
were at the same level.
Within rather broad technical limits, many configura-
tions are feasible. It must be remembered, however, that
more towers mean more cost.
Screening Lines with Trees. This would be effective in
reducing jeopardy to species that naturally avoid trees.
While many forest species are quite agile and avoid colli-
sions, trees in open country would attract raptors and
herons which are less agile.
Although this method may be feasible for distribution
lines, high-voltage lines often exceed 100 feet in height.
Trees of this size are not easily acquired or moved. Mass
grown trees for use with distribution lines would not be
expensive. The costs should be similiar to those of wind-
break trees used in the plains states.
Removing the Static Wire. There is evidence showing
that many birds are killed by collision with this small high
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Working Group Summaries
wire: thus, its removal would reduce the probability of
collision.
This suggestion is feasible and reduces line
construction costs. However, the static wire deflects
lightning strikes from the conductors. Because lightning
can cause outages, this will work only in lightning-free
areas.
Repelling Birds. Scare devices have considerable suc-
cess when birdS do not remain in the area long enough to
become accustomed to, and unafraid of, them. Flocking
species appear to acclimate more quickly (e.g., starlings
and Canada geese). However, there is no evidence that
scare devices attract or disorient birds.
Cost is quite low, and many methods such as flashers,
explosions, predator models, and various noises are avail~
able.
Preventing Distractions to Birds. Data indicate that
many collisions occur in conditions of good visibility when
the birds are distracted by predators, hunters, or other
human activities. The suggestion was made to eliminate
human access to areas of bird concentration and power-
lines. The difficulties lie in enforcement and land-use
control. These difficulties make such isolation impossible
except on refuges and other areas already controlled
principally for wildlife protection purposes. Obviously, this
situation applies only to bird concentration areas with
existing lines; new lines should not be built in such areas,
In those cases in which the land is already regulated,
costs are low. If land acquisition or easements are needed,
costs will increase quickly.
Compensating for Bird Losses
A fourth strategy suggested that both habitat and
individual birds are replaceable. When habitat conflicts
with lines that particular habitat can be sacrificed and
other similar habitat purchased. Ahernatively, game farms
can be built so birds can be raisedtocompensateforthose
lost to collision.
The notion seems feasible if one thinks only of those
species such as mallan:ls, which can be easily raised. In
1978, however, we simply do not know enough to ra'lse
181
Management Options
~--~-~~~--~----------~~--~----L
and restore all of the more than 200 species known to be
killed by powerlines. Line builders contend that the
number of some species killed is insignificant and can be
ignored.
Habitat replacement is limited by available similar
habitat. Many of our bird concentrations today exist be-
cause all other habitat has been destroyed.
The cost for either of these programs could be inexpen-
sive to very expensive, depending on local land prices or
which species_are jeopardized. There was no consensus
about who should pay for compensation.
SUMMARY
Most methods suggested here simply have not been
studied enough. Scientists, though personally convinced
the problem is serious, are reluctant to take a stand be-
cause they lack an empirical basis for any position. Utility
people, thinking of vast sums of money and equipment
involved in mitigation, find little data to convince them to
voluntarily change their route selection priorities.
Management Options
The group first addressed the question: What is the
extent of the bird/powerline problem? The following
statement summarizes most of the substantial comments:
"It is the concensus of this group that power lines have not
been proven to be a general hazard to bird movements.
However, there is a high likelihood that adverse impacts
would occur in a limited number of cases and under cer-
tain specific circumstances. Furthermore, although
significant mortality may not be proven for most individ-
ual situations, we recognize the implications of small,
cumulative impacts. The best solution to avoiding signifi-
Spencer Amend (chairman), Michael L. Avery, Robert Berg, FrankCassel,
Len J. Cernohous, Richard C. Crawford, Dale Fowler, GilbertS. Grant, J. A. R.
Hamilton, Jack M. Lee, Jr., W. Allen Miller, Dean Miller, Ben Pinkowski, Richard
L. Plunkett, Kent Schreiber, J. T. Tanner, RichardS. Thorsell, Howard Teasley,
Roger Vorderstrasse, Keith H. Wietecki.
182
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Working Group Summaries
cant individual problems and to minimizing overall
adverse impacts appears to lie in early communication
between powerline planners and wildlife interests. An
acceptable goal would be to identify potential problems far
enough in advance that needed facilities could be con-
structed with minimum delays and with minimum adverse
impacts on bird movements."
The group's second topic of discussion was an appro-
priate definition of management in this context. The first
proposed definition was one limitedtothetraditional wild-
life management approach-i.e., the manipulation of vari-
ous factors to produce a desired result. After some dis-
cussion, the definition was broadened to encompass those
elements of powerline decision processes that relate to
interactions with bird movements.
The management options identified by the group were,
therefore, three:
1. Determine whether a potential problem exists.
2. Avoid problem areas.
3. Mitigate.
Mitigation, the subject of another working group, is
recognized as being highly site and species specific. Be-
cause the mitigation and management options groups
considered similar situations, we focused on who has
responsibilities for exercising the three broad options and
when they should do so. The table on the next page
summarizes the various responsibilities, times, and
options discussed.
Several portions of the discussion led to the frustrat-
ing conclusion that adequate data bases do not exist in
many areas. This problem was considered by the research
priorities working group ..
One suggestion that deserves consideration is that
permit approval might be conditional where a problem is
suspected but cannot be proven. The condition would
be that the line be built and monitored and that if damage
is shown to occur, mitigation measures-including com-
pensation for losses-be initiated.
The final recommendation is that a reporting system
utilizing a standard form be tested by workers in industry,
government, and the private sector to document bird calli-
183
Research Needs
sions. This system, if proven workable on a small scale,
could be expanded to provide a source of useful data not
now available.
Management Options: Responsibilities, Priorities, and Timing
Option
Identify potential problems
Avoid problem areas
Mitigate
Powerline Construction Phases
Planning
*A, B, C
A, B,C
A, B,C
Construction Operation
A, B, C
*A, B, C
A, B, C
A, B, C
*A,B,C
*Identifies priority option at each phase.
A Identifies responsibility by utilities to exercise appropriate
option.
B Identifies responsibility by wildlife interests to exercise appro-
priate option.
C Identifies responsibility by licensing and regulatory authorities
to exercise appropriate option.
Research Needs
The work group on research needs considered five
questions. The essence of these deliberations is provided
below.
1. What gaps of knowledge extst m determmmq
the tmpact of transmtsston lmes on mtgra-
tory btrds?
It is easier to state what is known, rather than what is
not known, in addressing this question. We can state with
William L. Anderson, Joe Binder, Bob L. Burkholder, Edward Colson, Ron
Freeman, Milton Friend (chairman), Sidney A. Gauthreaux, Jr., Donald A.
Hammer, Carl Korschgen, Roger Kroodsma, Ira D. Luman, Richard L. Morgan,
Larry Thompson, William T. Tucker, Bob Welford, Jochen H. Wiese, Daniel E.
Willard.
184
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confidence that birds of a wide variety of species are ki lied
by collisions with powerlines. These collisions occur in
different types of habitats and at a variety of locations
throughout the United States. We also know thatthe prob-
ability of birds' being in flight is influenced by physical
factors such as weather conditions and patterns and the
biological characteristics of individual species as they
relate to time of year, breeding biology, and feeding
behavior. Flight must also occur within the vicinty of
power lines and within an elevation range at which a colli-
sion is possible (the strike zone).
The potential strike zone has three dimensions: the
length of the powerline, the vertical plane of wires
(perpendicular to the ground), and the horizontal plane of
wires (parallel to the ground). The vertical plane appears to
be far more important than the horizontal plane. How-
ever, the latter is important when birds are flushed from
below a powerline, when avian predators such as raptors
are pursuing prey in flight below them or on the ground,
and when birds are descending from high elevations to
land.
From this knowledge we can predict the general types
of conditions most I ikely to present the greatest prob-
abilities for bird collisions with powerlines. For example,
deteriorating weather conditions that lower the elevation
of migrating birds to the strike zone and reduce the visi-
bility of birds in flight within this zone increase the prob-
ability of collisions. Distractions to birds in flight within
this zone also increase the probability for collisions.
Distractions include the active pursuit of food while in
flight (e.g., a raptor pursuing a prey species or an insec-
tiverous feeder pursuing a swarm of invertebrates), court-
ship flights (e.g., the pursuit flight of one or more drake
mallards and a hen mallard), and escape flights (e.g., the
flushing of birds due to the approach of a predator, air-
craft, or man).
Biological and physical characteristics of various avian
species are also important in evaluating the potential for
collisions in the strike zone. The large body size and wing
span of eagles, cranes, and herons result in a large surface
area and a higher probability for a collision with a wire
185
Research Needs
than for blackbirds or teal. However, the visual acuity of
the species; its speed of flight; maneuverability; and
whether its flight tends to be solitary, in loose aggrega-
tions, or in dense aggregations interact with body size and
wing span as do the weather conditions and distractions
described above.
Species that feed their young at the nest have a greater
probability for wire strikes during the nesting season than
species that lead their young from the nest area at hatch-
ing, provided the feeding flights pass through the strike
area. For example, herons must make numerous daily
flights to provide food for both themselves and their young
until the young can leave the nest, while mallards leave
the nest with their broods as soon as the clutch hatches.
The physical location ofpowerlines relative to daily and
migratory flight patterns and the familiarity of the popula-
tion at risk with the location of these lines influences the
probability of collisions. Resident species, or those present
in an area for an extended period of time, undoubtedly
learn the location of powerlines, thereby reducing their
probability per flight for a collision with these lines from
that of migrants passing through the area. However, a line
that separates feeding areas from resting and roosting
areas necessitates that local birds traverse the strike area
at least twice a day.
Even though local birds may be aware ofthe location of
power lines, this advantage may be lost over time because
of thefrequencyoftravel within the strike zone. Avoidance
of the lines from familiarity can also be negated by
weather conditions or an escape flight, during which time
the bird's attention is elsewhere.
We know that habitats for migratory birds are altered
py powerlines. What we do not know is the magnitude of
bird losses due to collisions with powerlines, the long-
term effects of habitat alterations due to the construction
of these lines, or the indirect effects on bird populations
and movements that may result from the placement of a
powerline at a particular site. Therefore, the biological
significance of powerlines cannot be adequately assessed
at this time.
It is essential to recognize that the number of birds
186
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killed is not by itself an adequate measure of biological
significance. The number of individuals killed at a given
location must be related to population numbers for that
species at local, regional, and national levels. For example,
a powerline kill of 1,000 pintails in California has far less
biological significance than the loss of a single California
condor or the loss of an acre of critical breeding habitat for
a threatened or endangered species.
The effects of various physical factors such as visi-
bility, size, and configuration of lines and the design and
height of supporting structures are totally unknown. Also,
the contributions of various biological factors such as the
relative importance of collisions during migration move-
ments versus local movements, the frequency of colli-
sions within daily and seasonal time frames, and differ-
ences due to behavior and biology for various species are
insufficiently understood to allow comprehensive evalua-
tions. Even less is known about nonlethal effects of power-
line placement: avoidance of areas by birds following the
construction of powerlines, altered migrational move-
ments, altered physiological responses due to electro-
magnetic fields, and habitat alterations.
None of the above should be construed to mean that
bird collisions with wires or the placement of powerlines
are unimportant, only that many facts remain obscure.
These data must be obtained to effectively evaluate the
biological effects of powerlines at site-specific locations
(present or planned) and to develop mitigation against bird
collisions.
The following key questions represent data gaps that
deserve priority attention:
a. Where are the high risk areas?
b. What are high risk habitats?
c. What is the magnitude of bird collisions with pow-
erlines for the various bird species over specific
time periods?
d. What are the effects of powerlines on mortality,
flight behavior, and local distribution of birds;
what is the biological significance at local, region-
al, and continental levels?
187
Research Needs
e. What are the specific conditions that influence the
probability of bird collisions with powerlines?
f. What standard methods are available to develop
these missing data?
g. What are the relative effects of powerlines on birds
in migration, on birds in local movement, and on
birds in concentrations?
2. Hovy can these questwns be addressed on a
short-term basis?
Considerable data are available to evaluate the
potential for bird collisions with powerlines. These are
deficiencies, however (for instance, the inadequacy of
species and site-specific data for local situations). There-
fore, care must be exercised when extrapolating from
general to specific situations.
Bird movement and bird concentrations are of primary
concern in evaluating the potential for collisions with a
proposed powerline. National and regional information on
bird migration patterns and corridors is available for many
species. However, the more local the area, the more inade-
quate the information tends to be. Principal information
sources are the United States Fish and Wildlife Service
(Migratory Bird Habitat Laboratory and the Bird Banding
Laboratory), various state conservation agencies, the
Illinois Natural History Survey and others involved in radar
studies of bird migration, and field guides and other
publications dealing with the seasonal a·nd geographical
distribution of birds.
Bird concentrations for some species can be obtained
from various surveys conducted by natural resource
agencies and the National Audubon Society. Periodic bird
counts by local Audubon groups, counts conducted on
national wildlife refuges, and aerial surveys by federal and
state conservation agencies provide local data relative to
species diversity and relative abundance. These and other
data sources, fully utilized, will provide a reasonable
evaluation of bird populations within a proposed power-
line corridor during various periods of the year.
Information on the types of birds likely to collide with
188
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powerlines can be partially obtained from a review of wild-
life mortality data. Primary sources of information include
diagnostic laboratory records, bird rehabilitation and
rescue center records, national wildlife refuge records,
field notes, and the scientific literature. United States Fish
and Wildlife Service records on causes of eagle mortality
represent a substantial data base that extends over a
broad geographic area and spans more than 10 years.
These data provide an estimate of the proportion of deaths
due to collisions relative to other types of mortality in the
eagles examined.
Mortality data must be interpreted with great caution
due to inherent biases and variability. It is important to
assess the completeness of the examinations leading to
the diagnosis of mortality; to knQw how representative the
birds examined are relative to others that died and were
not examined; and, in some cases, it is importantto assess
the qualifications of the investigator who is determining
the cause of mortality.
Despite the inadequacies of mortality data, they are
valuable in evaluating the potential for bird collisions with
powerlines, so long as the absence of records document-
ing collisions of various species is not interpreted as
evidence that those species do not collide with power-
lines. Biological characteristics of the species (e.g., size
and coloration), habitat conditions, scavenger activities,
the magnitude of search efforts to detect mortality, and the
type of documentation of wildlife mortality (personal diary
versus publication in the scientific literature) all influence
the data base.
A better understanding of why birds collide with wires
and other inanimate objects is essential to minimize the
potential for such collisions. Therefore, considerable
insight can be gained by examining available information
on bird collisions with aircraft, radio towers, buildings, and
other objects. Literature searches on these subjects will
provide information relative to the circumstances involved
in bird collisions and will identify site-specific locations in
which long-term studies have been or are being carried
out.
The effects of powerlines on migratory birds extend
189
Research Needs
beyond direct mortality as a result of collisions. The
influence of these lines on bird migration and behavior is
poorly understood but must be considered in evaluating
powerline corridors. Electromagnetic effects have been a
subject of continued controversy. Review of the literature
on Project Seafarer (Sanguine) and E:llectric fields cur-
rently provides the best information on electromagnetic
effects.
Animal damage studies provide another potential
source of data for understanding bird/powerline inter-
actions. The Denver Wildlife Research Center of the U.S.
Fish and Wildlife Service has pioneered in the area of
electric fields and electronic devices to repulse birds and
animals from crops and livestock. The theoretical con-
siderations involved in these techniques and the results of
field and laboratory testing are relevant to predicting the
outcome of bird/powerline interactions involving electro-
magnetic fields. These studies are also relevant in
developing methods for repulsing birds from powerlines.
In addition to using existing data bases more advanta-
geously, a comprehensive response to each of the seven
questions outlined above should be formulated based on
what is . already known. Individuals from . various
disciplines should be involved to ensure the broad
coverage needed. Publication of these findings would pro-
vide a reference manual to guide power producers, con-
sumers, and natural resource agencies. Specific informa-
tion needs regarding what is not known will become
readily apparent as a result of this effort.
The development of standard methods for obtaining
this information represents the next logical short-term
step. This will help eliminate differences in interpreta-
tion. Part of this step should be the development of
standard methods for data recording so information can be
gathered at a central location for distribution to all those
needing it. Once these procedures have been imple-
mented, a wide variety of individuals can be involved to
supplement data gathering.
The short-term approach, then, is to identify-specific
information needs, develop standard methods for obtain-_
ing and recording this information, and returning it to
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Working Group Summaries
specific users through a central data bank. An example of
how this might work involves developing better mortality
data regarding bird collisions with powerlines. In this
hypothetical example, a network of diagnostic labora-
tories specializing in wildlife are identified to assist in
various mortality studies. Field investigators pick up dead
birds in their areas and record a variety of data such as age
of powerline, size of the line, and weather conditions
during the preceding and current 24-hour periods prior to
submitting this record to the appropriate diagnostic
laboratory with the bird specimens. After necropsy and
laboratory tests, the mortality findings are added to the
form, a copy is kept by the diagnostic laboratory, a copy is
returned to the field investigator, and the original is sentto
a central data bank. Computer retrieval and sorting allow
various approaches to the data.
3. What long-term research needs to be tnJttated
to evaluate the tmpact of transmtssion lme
corndors?
until information needs are more specifically defined,
only general comments can be made in response to this
question. A combination of field a~d laboratory studies will
be required to evaluate why birds collide with wires, how
serious the problem is, and what can be done to reduce the
probability of these collisions. Field studies should focus
on the highest predictable risk situations based on current
knowledge. Intensive long-term (5 to 20year)studies need
to be developed to address the entire impact of power-
lines on bird populations.
These studies should address successive changes in
the habitat disturbed by construction of a powerline and
the effects of these changes on the distribution of bird
populations at a local, regional. and national level; identify
changes in movement patterns as a result of powerline
placement; identify differences in response patterns by
different species at different times of the year; and identify
differences in effects on resident and staging bird popula-
tions versus transients.
Laboratory studies should focus on providing informa-
tion on why birds collide with objects. Studies of bird flight
191
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Research Needs
and vision are highly relevant since a greater understand-
ing of these two basic areas will provide for potential
mitigation through revised structural design of power-
lines and supporting structures. Other laboratory studies
need to focus on developing recording devices that will
automatically record bird collisions so that better evalua-
tions can be made relative to the seasonal and daily timing
of these collisions and the number of collisions that are
immediately fatal. Electromagnetic effects must be
studied to determine if they result in altered physiological
functions. The development of avoidance devices that can
be used at high-risk locations on a continual or seasonal
basis to repel birds from powerlines is another area of
laboratory research needed.
4. Who needs this knowledge, and who should
fund the research?
Private utility companies need a sound data base for
selecting powerline corridors that have minimal environ-
mental impacts and are still economically feasible.
Resource agencies must have the data to prepare envi-
ronmental assessments of proposed powerlines. Envi-
ronmental groups and others must have access to these
data to properly evaluate the environmental impact
assessments and statements. Mitigation of predicted
impacts also depends on this data base.
Despite the common need for these data, different
orientations of these groups result in different priorities
and, perhaps, different areas of responsibility. Utility
companies should not expect resource agencies to pro-
vide funds or other resources for redesigning and
engineering powerlines and supporting structures that
may be less hazardous to birds. However, state and federal
resource agencies should be primarily responsible for sup-
porting research efforts involving bird populations, habitat
changes, and bird migration. Both groups have an obliga-
tion to support research on the magnitude of bird colli-
sions with powerlines. Basic studies on flight, vision, and
avoidance mechanisms (to prevent bird strikes) have
implications for many areas of science. Therefore, these
studies appear appropriate for funding by the National
Science Foundation and other such agenCies.
192
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Working Group Summaries
5. How should information be transmitted?
Effective information exchange on a continuous basis
is needed to reduce the costs and time involved in mini-
mizing current information gaps. Information must be
transmitted rapidly enough for investigators to take advan-
tage of local field situations and current advances in
technical knowledge. One means is the Center for Short-
Lived Phenomena. Subscribers to this service are
immediately sent an Event Notification Report that pro-
vides the date, location, and source of the report along
with a brief description of the event. Issuance of a report is
dependent upon the Center's being notified of the event.
This notification system potentially provides interested
investigators the opportunity for on-site data gathering.
The brevity of these Event Notification Reports dictates
that other means of inform at ion exchange a I so be uti I ized.
Establishment of a quarterly journal, a monthly news-
letter, and an annual workshop are suitable forums for
exchanging detailed information. Of the three, the work-
shop may be the most useful for the short-term.
193
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Workshop
Summary
Stanley H. Anderson
U.S. Fish and Wildlife SeiVice
During the past 2112 days we have gathered to try to
evaluate the impact of bird collisions with transmission
lines on avian populations. The goals have been (1) to
determine what we knew about the question, (2)tofind out
what results could be expected from known management
techniques, and (3) to determine the areas of uncertainty
and the means of understanding these areas. We have dis-
cussed many aspects of these questions and tried to
resolve some of the difficulties .. We have suggested short-
term solutions and posed questions to establish long-term
efforts to promote a more complete understanding of the
subject.
Transmission lines are a source of mortality to bird
populations as discussed in several papers presented at
the conference. However, at this time we have not assim-
ilated the data on the percentage of population mortality,
the effects of scavengers on bird death counts, or the
actual number of collisions with transmission lines.
Further studies of the effects on populations are
needed if we are to understand the complete scope of this
question on avian mortality. Rare or endangered species
195
Stanley H. Anderson
are of particular concern if any individual of such
populations collides with transmission lines. The loss of a
single Everglade kite or whooping crane can severely alter
those populations. Most other populations produce more
young than the habitat can maintain. In this case we must
determine whether natural population controls are being
partly taken over by transmission line collisions. These
types of data are fairly easy to collect.
Every region has specific problems which require a
particular type of evaluation for proposed transmission
lines. Local habitat and bird behavior must be studied in
each region. Planners must consider how changes in rout-
ing, tower design, and land use can reduce avian colli-
sions in each region. Bird maneuverability, seasonal
behavioral changes, flight patterns, and habitat use must
be known in normal and adverse weather conditions.
It is apparent that the limited data currently synthe-
sized is primarily on raptors and waterfowl because these
are more conspicuous. Even so, their data bases are inade-
quate to make reliable decisions on line placement. Data
on other species of birds are virtually nonexistent.
The utility companies are faced with many interest
groups when proposing a transmission line. Private land
owners, conservationists, and local and national govern-
ments must be satisfied in the planning and construction
phases. While the aesthetics of the lines and towers domi-
nate thinking once government regulations have been
satisfied, the effect of the transmission lines on wildlife,
particularly migratory birds, is not known. The initiation of
studies to assist planners and engineers in placing trans-
mission lines and designing structures that minimize the
impact on migratory birds would benefit manyofthe inter-
ested groups that must be satisfied.
We have not yet assimilated all the data on the impact
of transmission lines on avian populations. This should be
our first order of business. Next, we should learn more
about the techniques to evaluate flight patterns and use
these techniques to provide planners with information on
desirable and undesirable line locations. We should con-
sider habitat type and suggest where habitat alteration
due to transmission line siting might be managed to bene-
196
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Workshop Summary
fit wildlife and where critical habitat or habitat features
exist that should be avoided in transmission line siting.
Means of deterring birds in flight from lines and towers
should be investigated. Noise, lights, and colors that are
effective in different regions should be considered. Poten-
tial design changes in towers should be studied.
There is a great deal of interest in the powerline-avian
mortality relationship as is indicated by the requests for
attendance at this workshop. The concern, however,
varies in different regions. As professionals, we have an
obligation to bring together information and suggest forms
of data to answer the questions. This does not mean we
need to have a mass of different data collections, but we
must answer basic questions to help designers and those
evaluating the impact of transmission lines to make the
best decisions. The question is, then, national in scope as
far as data assimilation techniques and biological impact
are concerned. We are not suggesting national regula-
tions with additional steps of applications and approval
when utility companies propose transmission lines. Each
transmission line siting poses regional questions. Local
engineers, planners, and biologists must evaluate the
routing, the biological, and, ultimately, the social ques-
tions affecting local areas.
197
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Data Bas·e on
Avian Mortality on
Man-Made Structures
Nancy S. Dailey
Oak Ridge National Laboratory
A computerized data base concerning avian mortality
on man-made structures is available for searching at the
Ecological Sciences Information Center of the Information
Center Complex, Information Division, Oak Ridge National
Laboratory. It is one of four data bases sponsored by the
U.S. Department of the Interior, Fish and Wildlife Service,
National Power Plant Team, in Ann Arbor, Michigan.
This data base, which contains entries from the avail-
able literature, provides information on avian mortality
from either collision into or electrocution on man-made
structures. Primary emphasis has been placed on avian
collision with obstacles such as television and radio
towers, airport ceilometers, transmission lines, and
cooling towers .. Other structures included in the studies
are fences, glass walls and windows, lighthouses,
telegraph and telephone wires, buildings, monuments,
smokestacks, and water towers. Collision studies involve
field counts with identification of victims and field
observations of both flight behavior near structures and
avian attraction to I ights. Studies which evaluate
migration patternsby using collision data and whir.h de-
scribe the impact of weather on migration and flight pat-
199
Nancy S. Dailey
terns have also been included. Other reports examine the
causes of death and injury from impacts, report victim
morphometry and physiology, evaluate species suscepti-
bility to collision, and assess the impact of predation on
study reliability. Related studies describe the impacts on
birds from the siting of transmission facilities in wetlands
or migratory flyways or provide recommendations for such
sitings. Avian electrocution studies, which cover both
electric transmission structures and electric fences,
identify and assess bird fatalities, examine the activities
resulting in death, identify problem locations and lethal
structure designs, and recommend structural modifica-
tions to reduce fatalities. References from the data base
which pertain solely to avian transmission wire strikes are
found in the following paper.
Resources and services of the Ecological Sciences
Information Center are available to all individuals.
Searches are performed without charge to DOE staff
members and to researchers working on directly related
DOE-funded projects. Searches are also performed
without charge at the request of the sponsor. For all
others, a minimum fee of $30, which covers the charges
for most searches, is assessed. Fees are billed through the
National Technical Information Service, Springfield,
Virginia.
Information searches may be initiated by contacting
the Ecological Sciences Information Center and giving
complete details of the request. Specific searches can be
performed for authors, corporate author, keywords, sub-
ject categories, geographic location, taxon, and title. Mail
written requests to Nancy S. Dailey or Helen Pfuderer,
Ecological Sciences Information Center, Information
Center Complex, Oak Ridge National Laboratory, P.O. Box
X, Oak Ridge, Tennessee 37830, or telephone (615) 483-
8611, Ext. 3-6173 (FTS: 850-6524). Additional assistance
may be obtained by contacting Gerald Ulrikson, Informa-
tion Center Complex, Oak Ridge National Laboratory, Oak
Ridge, Tennessee 37830.
ACKNOWLEDGMENT
Oak Ridge National Laboratory is operated by Union
Carbide Corporation for the U.S. Department of Energy
under contract number W-7405-eng-26.
200
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A_Selected
Bibliography on Bird
Mortality Involving
Overhead Wires
Nancy S. Dailey
Oak Ridge National Laboratory
Michael L. Avery
National Power Plant Team
U.S. Fish and Wildlife Service
Reports on bird losses due to collisions with overhead
wires date back to the 1870s; however, until recently,
most of the reports were random observations containing
little more than a list of the casualties. In the past several
years, the body of literature on this topic has increased
dramatically, perhaps partially due to an increased public
awareness.
The following selected references, mostly from the
1970s, deal with bird mortality caused by overhead wires.
Three papers (Fog 1970, Gunter 1956, and Hunt 1972)
describe avian flight behavior in the vicinity of transmis-
sion lines, and a few reports discuss mitigative measures.
The bibliographies compiled by Dailey (1978), Thompson
(1977), and Weir (1976) contain numerous references on
a spectrum of related topics. Several foreign reports are
included to emphasize that the mortality problem is not
restricted to the United States.
Copies of all references cited are available from the
Ecological Sciences Information Center, Oak Ridge
National Laboratory, Oak Ridge, Tennessee, 37830. This
list is part of an annotated bibliography, now in prepara-
201
------------------l.J
Nancy S. Dailey, Michael L. Avery
tion, concerning bird mortality at all man-made struc-
tures.
Anderson, W. L.ln press. Waterfowl Collisions with Power
Lines at a Coal-Fired Power Plant. Wildlife Society
Bulletin.
Anderson, W. L.; Hurley, S.S.; Seets, J. W. 1975. Water-
fowl Studies at Lake Sangchris. Illinois Natural History
Survey, Urbana, Illinois.
Anderson-Harild, P.; Bloch, D. 1973. Birds killed by over-
head wires in some localities in Denmark. Dansk Orni-
thologisk Forenings Tiddsskrift 67(1-2):15-23.
Anonymous. 1976. Waterfowl Power Line Collisions.
Illinois Natural History Survey, Report Number 160,
pp. 3-4.
Arend, P. H. [1970.] The Ecological Impact of Trans-
mission Lines on the Wildlife of San Francisco Bay.
Pacific Power and Light Company Report.
Beak Consultants, Inc. 1977. A Waterfowl Study of
Selected Sites Within the Klamath Basin and Warner
Valley, Oregon.
Beer, J. V., and Ogilvie, M.A. 1972. "Mortality." In: Scott,
P., and the Wildfowl Trust, The Swans. Boston: Houghton
Mifflin Company, pp.125-45.
Blokpoel, H., and Hatch, D.R.M. 1976. Snow geese,
disturbed by aircraft, crash into power lines. Canad. Field-
Nat. 90(2): 195.
Boyd, H. 1961. Reported casualties to ringed ducks in the
spring and summer. Wildfowl Trust 12:144-46.
Boyd, H., and Ogilvie, M. 1964. Losses of mute swans in
England in the winter of 1962-3. Wildfowl Trust 15:37-39.
Brooke, M. del. 1970. Some aspects of mute swan move-
ment and mortality. Cambridge Bird Club 44:44-47.
202
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A Selected Bibliography
Bub, H. 1955. Observations on the autumn migration in
the area between the Sea of Azov and the Caspian. Ibis
97:25-37.
Cornwell, G. W., and Hochbaum, H. A. 1971. Collisions
with wires - a source of anatid mortality. Wilson Bull.
83(3):305-6.
Coues, E. 1876. The destruction of birds by telegraph wire.
Amer. Nat. 1 0( 12):734-36.
Dailey, N. S. 1978. Environmental Aspects of Transmis-
sion Lines: A Selected, Annotated Bibliography. Oak
Ridge National Laboratory, ORNL/EIS-122.
Dinesman, L. G. 1947. On the destruction of some birds in
hitting telegraph wires. Zoological Journal Moscow,
26:171-76.
D'Ombrain, A. F. 1945. Migratory birds and overhead
wires. Emu 45(2): 173-7 4.
Emerson, W. 0. 1904. Destruction of birds by wires.
Condor 6(2):37-38.
Fitzner, R. E. 1975. Owl mortality on fences and utility
lines. Raptor Res. 9(3-4):55-57.
Flegg, J. J. and Cox, C. J. 1975. Mortality in the black-
headed gull. British Birds 68(1 ):437-49.
Flegg, J. J. M. and Morgan, R. A. 1976. Mortality in British
gulls. Ringing and Migration 1 (2):66-74.
Fog, J. 1970. Effect of high voltage electrical transmis-
sion lines on flying height of anatidae. Flora Fauna,
76:141-44 (Oak Ridge National Laboratory translation,
ORNL-tr-4387).
Glue, D. E. 1971. Ringing recoverycircumstancesofsmall
birds of prey. Bird Study 18(3):137-46.
Gunter, G. 1956. On the reluctance of gulls to fly under
objects. Auk 73:131-32.
203
Nancy S. Dailey, Michael L. Avery
Gustefson, S.P., and Geis, J. L. 1976. Prairie Island
Nuclear Generating Plant Environmental Monitoring and
Ecological Studies Program -Annual Report Vol. 2.
Northern States Power Company.
Harrison, J. 1963. Heavy mortality of mute swans from
electrocution. Wildfowl Trust. 14:164-65.
Hiltunen, E. 1953. On electric and telephone wire acci-
dents in birds. Suomen Riista 8:70-76, 222-23.
Hochbaum, H. A. 1960. Travels and Traditions of Water-
fowl. Newton, Massachusetts: Charles T. Branford
Company.
Holyoak, D. 1971. Movements and mortality of corvidae.
Bird Study 18(2):97-1 06.
Hunt, R. A. 1972. "Some field and court case experiences
with waterfowl and electrical powerlines." In Proceed-
ings Mtdwest Fish and Wildlife Conference. Des Moines,
Iowa, 34:60.
Jennings, A R. 1961. An analysis of 1,000 deaths of wild
birds. Bird Study 8(1 ):25-31.
Kiel, D. W., and Cassel, J. F. Unpublished. Avian mortality
study at Underwood, North Dakota, fall report. North
Dakota State University, Fargo.
Krapu, G. L. 1974. Avian mortality from collisions with
overhead wires in North Dakota. Prairie Nat. 6(1 ):1-6.
Lee, J. M., Jr. In press. Bird collisions with transmission
lines-a preliminary study of a 230 kv transmission line.
Wilson Bull.
Lee, J. M., Jr. Unpublished. A Summary of Reports of Bird
Collision with Power and Communications Lines. Bonne-
ville Power Administration.
McKenna, M.G., and Allard, G. E. 1976. Avian mortality
from wire collisions. North Dakota Outdoors 39(5):16-18.
204
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A ~elected Bibliography
Meyer, L. W. 1977. "Sage grouse collisions on ten mile
powerline (230 kV)." U.S. Department of the Interior,
Bureau of Land Management, unpublished memo-
randum.
Morgan, R., and Glue, D. 1977. Breeding, mortality and
movements of kingfishers. Bird Study 24(1 ):15-24.
Ogilvie, M.A. 1967. Population changes and mortality of
the mute swan in Britain. Wildfowl Trust 18:64-73.
Owen, M., and Cadbury, C. J. 1975. The ecology and
mortality of swans at the Ouse Washes, England. Wild-
fowl 26:31-42.
Schroeder, C. G. 1977. Geese hit power transmission line .
North Dakota Outdoors 40(2):(inside front cover).
Scott, R. E.; Roberts, L. J.; and Cadbury, C. J. 1972. Bird
deaths from power lines at Dungeness. British Birds
65(7):273-86.
Siegfried,_ W. R. 1972. Ruddy ducks colliding with wires.
Wilson Bull. 84(4):486-87.
Sisson, J. 1975. Death trap. National Wildlife 13(3): 18.
Stahleker, D. W. 1975. "Impacts of a 230-kV transmission
line on Great Plains wildlife." M.S. Thesis, Ft. Collins:
Colorado State University.
Stout, I. J. 1967. "The nature and pattern of nonhunting
mortality in fledged North American waterfowl." M.S.
Thesis, Blacksburg: Virginia Polytechnic Institute.
Stout, I. J., and Cornwell, G. W. 1976. Nonhunting
mortality of fledged North American waterk·'lll. J. Wild!.
Manage. 40(4):681-93.
Thompson, L. S. 1977. Overhead TransmissiL 1 Lines:
Impact on Wildlife. Montana Department of 'atural
Resources and Conservation, Research Report Num 1r 2 .
205
Nancy S. Dailey, Michael L. Avery
U. S. Department of the Interior, Bureau of Land
Management. 1977. Final Environmental Statement
Proposed 500 kV Powerline Midpoint. Idaho-Medford,
Oregon. 2 vols.
U. S. Nuclear Regulatory Commission. 1975. Final
Environmental Statement Related to Operation of Davis-
Besse Nuclear Power Station Unit 1. NUREG-75-097, PB-
246 1 83, 95 pp.
Weir, D. N. 1971. Mortality of hawks and owls in Speyside.
Bird Study 18(3):147-54.
Weir, R. D. 1976. Annotated bibliography of bird kills at
man-made obstacles: a review of the state of the art and
solutions. Canad. Wildl. Serv., Ontario Region, Ottawa.
Wiese, J. H. 1976. A Study of the Reproductive Biology of
Herons. Egrets, and Ibis Nesting on Pea Patch Island. Del-
marva Power and Light Company.
Wiese, J. H. 1977. A Study of the Reproductive Biology of
Herons. Egrets. and Ibis Nesting on Pea Patch Island. Del-
marva Power and Light Company.
Willard, D. E., and Willard, B. J. Unpublished. Interaction
Between Some Human Obstacles and Birds. University of
Wisconsin, Environmental Awareness Center.
Willard, D. E.; Harris, J. T.; and Jaeger, M. J. 1977. The
Impact of a Proposed 500 kV Transmission Line on
Waterfowl and Other Birds. Final Report. D. E. Willard and
Associates.
Willard, D. E., and Willard, B. J. In press. The effects of
obstacles on birds. J. of Environmental Manage.
Yakobi, V. E. 1974. Biological Basis of Bird Strikes Pre-
vention. Moscow: Nauka.
ACKNOWLEDGMENT
Oak Ridge National Laboratory is operated by Union
Carbide Corporation for the U.S. Department of Engery
under contract number W-7405-eng-26.
206
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Participants
Mr. Spencer Amend
Kansas Forestry, Fish,
and Game Commission
Route 2, Box 54A
Pratt, Kansas 67124
Dr. Stanley H. Anderson
Migratory Nongame Birds ·
Working Group
Assignments
Mitigation,
Management
Options
Conference
Chairman
Migratory Bird and Habitat Research Lab
U. S. Fish and Wildlife Service
Laurel, Maryland 20811
Mr. William L. Anderson
Division of Wildlife Research
Illinois Department of Conservation
605 State Office Building
Springfield, Illinois 62706
Behavior,
Research
Needs
207
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Participants
[
Mr. Michael LAvery Habitat,
(Now with the National Power Management f~
Plant Team, U.S. Fish and Options Lj
Wildlife Service)
231 Gibson Road [ Annapolis, Maryland 21401
Mr. Robert Berg Habitat, [ U. S. Fish and Wildlife Service Management
P. 0. Box 1306 Options
Albuquerque, New Mexico 87103 I
Mr. Joe Binder Mitigation,
l_;
Rural Electrification Administration Research c South Agriculture Buirding Needs
Room 2232
Washington, D. C. 20250
[ Mr. Bob L. Burkholder Habitat, ~I
500 Multnomah, NE Research
Portland, Oregon 97208 Needs [
Dr. Frank Cassel Behavior,
Zoology Department Management [ North Dakota State University Options
Fargo, North Dakota 58102
len J. Cernohous Habitat, c·
Bismarck Area Office Management r
U. S. Fish and Wildlife Service Options \
P. 0. Box 1897 L Bismarck, North Dakota 58501
Mr. Edward W. Colson Habitat, L Pacific Gas and Electric Research
3400 Crow Canyon Road Needs
San Ramon, California 94583 Li
Mr. Richard C. Crawford Mitigation,
Tennessee Valley Authority Management L Chattanooga, Tennessee 37401 Options
208 [
---~ ----------------
Participants
.,
--~
Nancy S. Dailey
~ Ecological Science Information Center
'----'
ORNL, X-1 0, Building 2029
Oak Ridge, Tennessee 37830
I Mr. Dale K. Fowler Habitat,
'--' Tennessee Valley Authority Management
,., Norris, Tennessee 37828 Options
L Mr. Ron Freeman Mitigation,
Woodward-Clyde Consultants Research c 3489 Kurtz Street Needs.
San Diego, California 92110
[J Dr. Milton Friend Behavior,
National Fish and Wildlife Health Lab Research
University of Wisconsin Needs
[ c/o Department of Veterinary Science
1655 Linden Drive
Madison, Wisconsin 53706
[ Dr. Sidney A. Gauthreaux, Jr. Behavior,
Department of Zoology Research
B Clemson University Needs
Clemson, South Carolina 29631
D
Dr. Gilbert S. Grant Behavior,
University of California Management
at Los Angeles Option
~
Los Angeles, California 90024
G Dr. J. A. R. Hamilton Habitat,
920 S. W. 6th Avenue Management c Pacific Power and Light Company Options
Portland, Oregon 97204
n Mr. Donald A. Hammer Behavior,
_JI Division of Forestry, Fisheries and Research
Wildlife Development Needs
.r-") Tennessee Valley Authority
__. Norris, Tennessee 37828
[ 209
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l '
Participants
[
Dr. Kenneth Hoover Steering
National Power Plant Team Committee [ U. S. Fish and Wildlife Service
1451 Green Road
Ann Arbor, Michigan 48105 [
Dr. Philip L. Johnson, Steering
Oak Ridge Associated Universities Committee [ P. 0. Box 117
Oak Ridge, Tennessee 37830
Mr. Carl Korschgen Behavior, c U. S. Fish and Wildlife Service Research
LaCrosse, Wisconsin 54601 Needs
Dr. Roger L. Kroodsma Habitat, c
Environmental Sciences Division Research
Oak Ridge National Laboratory Needs c Oak Ridge, Tennessee 37830
Mr. Jack M. Lee, Jr. Habitat, [ Bonneville Power Administration Management
P. 0. Box 3621 Options
Portland, Oregon 97208 c Mr. Ira D. Luman Habitat,
Bureau of Land Management Research c~ P. 0. Box 2865 Needs
Portland, Oregon 97208
I
Mr. W. Allen Miller Mitigation, [-
Tennessee Valley Authority Management
701 Chattanooga Bank Building Options
Chattanooga, Tennessee 37401 c
Mr. Dean Miller Mitigation,
Public Service Company of Colorado Management [. P. 0. Box 840 Option
Denver, Colorado 80201
["
'
210 [
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Participants
c
Mr. Richard L. Morgan Behavior,
[ U. S. Fish and Wildlife Service Research
2953 West Indian School Road Needs
Phoenix, Arizona 85017
[ Mr. Ben Pinkowski Habitat,
NUS Corporation Management
1910 Cochran Road Options
[ Pittsburgh, Pennsylvania 15220
Richard L. Plunkett Behavior,
0 National Audubon Society Management
950 3rd Avenue Options
New York, New York 10022
D Dr. Kent Schreiber Behavior,
National Power Plant Team Management
0 U. S. Fish and Wildlife Service Options
Ann Arbor, Michigan 48015
[ Dr. J. T. Tanner Habitat,
Department of Zoology Management
University of Tennessee Options
D Knoxville, Tennessee 37916
'
Mr. Larry S. Thompson Mitigation,
6 Energy Planning Division Research
Montana Department of Natural Needs
Resources and Conservation
C=J 32 South Ewing
Helena, Montana 59601
u
Mr. Richard S. Thorsell Mitigation, c Edison Electric Institute Management
1140 Connecticut Avenue, N.W. Options
Washington, D. C. 20036 c
c
[ 211
----·--···----~----------··------------·---lj
Participants
Mr. Howard Teasley
Economic Research
Public Utility Commission of Oregon
Labor and Industries Building
Salem, Oregon 97310
Mr. William T. Tucker
United Engineers and Constructors
100 Summer Street
Boston, Massachusetts 0211 0
Mr. Roger Vorderstrasse
U.S. Fish and Wildlife Service
727 NE 24th Avenue
Portland, Oregon 97232
Mr. Bob Welford
Office of Biological Services
U. S. Fish and Wildlife Service
Federal Building, Fort Snelling
Twin Cities, Minnesota 55111
Mr. Jochen H. Wiese
P. 0. Box 7808
Newark, Delaware 19711
Mr. Keith H. Wietecki
Project Supervisor
Transmission Line Routing
Northern State Power Commission
414 Nicollet Mall
Minneapolis, Minnesota 55401
Dr. Daniel E. Willard
School of Public and Environmental
Affairs
Indiana University
Bloomington, Indiana 4 7401
212
Mitigation,
Management
Options
Habitat,
Research
Needs
Mitigation,
Management
Options
Behavior,
Research
Needs
Habitat,
Research
·Needs
Mitigation,
Management
Options
Mitigation,
Research
Needs
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