HomeMy WebLinkAboutAPA398SUSITNA HYDROELECTRIC PROJECT
ENVIRONMENTAL STUDIES
SUBTASK 7.11: BIROS AND NON-GAME MAMMALS
PHASE I REPORT
APRIL, 1982
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ALASKA POWER AUTHORITY
SUSITNA HYDROELECTRIC PROJECT
ENVIRONMENTAL STUDIES PHASE I FINAL REPORT
SUBTASK 7.11
BIRDS AND NON-GANE MAMMALS
April 1982
by
Brina Kessel, Principal Investigator
Stephen 0. MacDonald
-Daniel D. Gibson
Brian A. Cooper
and
Betty A. Anderson
MAY 1 7 1982
ARLis
L .b . Alaska Resources 1 rary & Info · An ...,__ nnatwn Se.rvu::es c~ru.rage, Alaska
University of Alaska Museum
Fairbanks; Alaska 99701
SUMMARY
To aid in determining the potential effects that the proposed Susitna
Hydroelectric Project might have on the fauna of the upper Susitna River
Basin, field studies on birds and small (non-game) mammals were con-
ducted from 6 July to 4 October 1980, 8 to 10 February 1981, and
17 April to 23 October 1981. The overall study area extended from near
Sherman on the west to the mouth of the Maclaren River on the east and
for approximately 15 km {10 miles) on either side of the Susitna River
channel. Within this region, we 1) established twelve 10-ha (25-acre)
bird census plots and 49 small mammal trapline transects and sampled
populations on them, 2) flew aerial waterfowl surveys in spring 1981 and
in falls 1980 and 1981, and conducted ground surveys of 28 waterbodies
(20.5 km 2 wetlands) in July 1981, 3) flew surveys of cliff habitat along
the Susitna River and its tributaries to determine use by raptors and
ravens in July 1980 and May 1981, and made ground visits during 1981 to
the vicinity of all 1980 and 1981 active sites, 4) undertook frequent
general surveys to obtain supplemental information about the birds and
small mammals of the region, and 5) measured up to 60 habitat variables
on the bird census plots and sma11 mammal trapl ine transects for
subsequent analyses of animal species-habitat relationships. Sites for
the bird census plots and small mammal trapl i ne transects were selected
to represent as broad a spectrum as possible of the various vegetation
types used by small mammals and terrestrial birds in the region.
During the study period, 135 specie~ of birds were recorded in the
region; the Common Redpoll, Savannah Sparrow, White-crowned Sparrow,
Lapland Longspur, and Tree Sparrow were the most numerous. Fifteen
species were ranked as rare in the region, mostly birds at the periphery
of their geographic ranges or for which appropriate habitat was lacking.·
All are represented by larger !)opulations in other portions of Alaska.
Population levels among the different habitats varied greatly.
Generally, the forest and woodland habitats supported higher densities
i
and/or biomasses of birds than the shrub communities. Highest densities
in forests were found at the downstream· (Shennan) Cottonwood Forest
plot, the lowest in the White Spruce Forest plot at the mouth of Kosina
Creek. Of the shrub habitats, Low-Medium Willow Shrub had the highest
densities and the Dwarf Shrub-Alpine Tundra, the lowest. Tall Alder
Shrub also had low densities. Alpine tundra areas had the lowest bird
usage, but supported some bird species generally not found in other
habitats.
The wetlands of the region supported relatively few waterbirds, both
during summer and during migratory periods. Densities of 23.8 adults/km 2
of wetlands in July 1981 were one-fifth those of the upper Tanana River
Valley, east-central Alaska. The region was of less importance to
migratory waterfowl in spring than fall, primarily because ice breakup
did not occur until after the main spring migratory movement of many
ducks; during both seasons, most waterbodies received far less use than
those in the upper Tanana Valley.
The two most important waterbodies in the immediate vicinity of proposed
impoundments were Stephan and Murder lakes. In add.ition to supporting
relatively high numbers of species and individuals, they had the longest
ice-free season and thus were important to early spring and late fall
mi~rants. Swans used these lakes until late October.
During 1980 and 1981; 43 raptor/raven nest sites were found, 20 of which
were inactive in both years. Of the 23 active sites, five were used
both years, each year by the same species. These active sites included
ten of Golden Eagle, six of Bald Eagle, four of Common Raven, one,
·perhaps two, of Gyrfalcon, and one of Goshawk. A single observation of
an Osprey was reported during the two seasons of study. There were no
confinned sir11tings of Peregrine Falcons.
Of the 16+ members of the Susitna River Basin's small mammal fauna, the
most abundant and widespread were masked shrew, northern red-backed
i i
vole, and arctic ground squirrel. The last two are probably the most
important prey species for bird and mammal predators. Trapline capture
infonnation indicated considerable temporal variation in population
levels for most shrews and voles, but their relative abundance rankings
remained the same. Patterns of habitat occupancy among _these species
indicated that shrews and red-backed voles were habitat generalists,
exploiting a wide range of vegetation types, while Microtus and lemmings
were habitat specialists, using a narrow range of tundra and herbaceous
vegetation types. r~eadow voles and singing voles were the most selec-
tive, the former preferring wet-mesic sedge-grass meadows and the
latter, herbaceous shrub tundra. Habitat occupancy patterns were
affected by changes in density and probable species interactions.
Call a red pikas and hoary marmots were locally common in the alpine zone
of the region, while red squirrels, snowshoe hares, and porcupines were
fairly common to uncommon in forest and shrubland at lower elevations.
The major impacts of the Susitna Hydroelectric Project would be from
habitat destruction due to flooding and from a range of habitat altera-
tions due to various construction and operational factors. Flooding
would destroy a large percentage of the riparian cliff habitat used by
nesting raptors and ravens. It would also inundate most of the major
forest habitats upriver of the Devil Canyon dam site, habitats that
support the highest avifaunal occupancy ievels in the region and support
bird and mammal species unable to use non-forested habitats. In all,
the breeding habitat used by over 40,000 pairs of small-and medium-
sized upland birds waul d be inundated. Flooding of the fl uvi ati 1 e
shorelines and alluvia, both along the Susitna River and up the mouths
of tributary creeks, would destroy breeding habitat of a few bird
species and wintering habitat of the Dipper. It would also deprive
early spring migrant waterfowl of (,ne of the first sources of open water
in the region--the rapidly flowing waters of the Susitna River. The new
impoundments could provide habitat for waterbirds, but the degree of
iii
utilization would depend upon the rate and kind of development of food
resources in the lakes. The drawdown zone would be an ecological desert
for small mammals, but would probably be used in May by migrant
shorebirds.
Impacts of other habitat alterations would depend on the type of altera-
tion, i.e., which habitats would be destroyed or altered or which
replacement habitats developed. Birds and small mammals dependent on
the destroyed or altered habitats would disappear, whereas new habitats
fanned would increase populations of species that favor the newly
created habitats. The construction zones for building and operation and
the access road right-of-way and borrow areas waul d destroy {or alter in
the case of borrow areas) the breeding habitat used by about 60,000
pairs of small-and medium-sized upland birds. Generally, impacts on
regional populations from forest destruction would be greater than those
from destruction of shrub habitats. Other than eliminating entire
communities through habitat destruction, some of the most striking
anticipated impacts of habitat changes would be increased populations of
ground squirrels, Mew Gulls, ravens, and magpies about human habitations
and/or refuse sites and increased populations of ground squirrels,
tundra anc.. ·meadow voles, and several sparrow species along the edges of
access roads.
Impacts would also result from direct disturbance to animals by various
human activities. The most prominent of these would be ground and
aerial activity too close to raptor nest sites during the breeding
season, and too close to wetlands during the ice-free season. Estab-
lishment of habitations near wetlands would also improve human access to
these areas and increase various types of disturbance, including
hunting.
iv
PROPOSED DEVELOPMENT
Two major reservoirs would be formed in the full-basin development plan
for the proposed Susitna Hydroelectric Project. The larger reservoir
would extend 77 km {48 miles) upstream of the Watana site and have an
average width of about 2 km (1 mile) an~ a maximum width of 8 km (5 miles).
The Watana reservoir would have a surface area of 154 km 2 {38,000 acres)
and a maximum depth of about 207m (680 ft) at normal operating level.
The Devil Canyon reservoir would be about 42 km (26 miles) long and 1 km (0.5
mile) wide at its widest point. A surface area of 32 km 2 {7,800 acres) and
a maximum depth of about 168m (550ft) would exist at normal operating level.
·Staged development is planned. An initial installation of 680-MW of capacity
at Watana would be available to the system in 1993 and 340 MW would be added
in 1994. If the mid-range forecast in growth in energy demand were realized,
Devil Canyon would be completed by· 2002 and would have an installed capacity
of 600 MW.
The Watana dam would be an earth-fill structure, with a maximum height of
270m (885 ft), a crest length of 1250 m (4,100 ft), and a total volume of
about 47,400,000 m3 (62,000,000 yd 3 ). During construction, the river would
be diverted through two concrete-lined diversion tunnels, each 11.5 m (38ft)
in diameter, in the north bank of the river. Upstream and downstream
cofferdams would protect the dam construction area. The power intake would
include an approach channel in rock on the north bank. A multilevel,
reinforced concrete, gated intake structure capable of operating over a
full 43-m (140-ft) drawdown range would be constructed.
The Devil Canyon dam would be a double-curved arch structure with a maximum
height of about 197m (645 ft) and a crest elevation of 446 m (1463 ft). Tha
crest would be a uniform 6-m (20-ft) width and the maximum base width, 27 m
(90ft). A rock-fill saddle dam on the south bank of the river would be
constructed to a maximum height of about 75 m (245 ft) above foundation
v
1 evel. The po\'ler intake on the north bank waul d include an approach
channel in rock, leading to a reinforced concrete gate structure, which
would accommodate a maximum drawdown of 17m (55ft). Flow construction
would be diverted through a single 9-m-diameter (30-ft-diameter) concrete-
lined pressure tunnel in the south bank. Cofferdams and the diversion
tunnel would provide protection against floods during construction.
About 2.5 yr of average streamflow would be required to fill the Watana
reservoir. Filling would commence after dam construction had proceeded
to a point where impoundment concurrent with continued construction
could be accommodated. Post-project flows would be lower in summer and
higher in winter than current conditions. Downstream of the project,
differences between pre-and post-project flow conditions would be
progressively less pronounced, because the entire upper basin contributes
less than 20% of the total discharge into Cook Inlet.
The selected access plan consists of a road from a railhead at Gold
Creek to Devil Canyon on the south side of the river. At Devil Canyon
the road would cross the Susitna and proceed east to the Watana site on
the north side of the river. The plan also includes access by road
connecting Gold Creek to the Parks Highway. Construction of a limited
access between Gold Creek and the Watana site, by way of a pioneer road,
would commence in mid-1983. Road access from the Parks Highway would be
deferred until after award of a federal license for the project. The
pioneer road would be rendered impassable if the project did not proceed.
The selected transmission line route associated with the Susitna project
would roughly parallel, but not be adjacent to, the access route between
Gold Creek and the Watana dam site. At Gold Creek, the line would
connect with the Rail belt In terti e. Between Willow and Anchorage, the
route would extend in a southerly direction to a point west of Anchorage,
where undersea cables would cross Knik Arm. Between Willow and Healy,
the route would utilize the transmission corridor previously selected by
the Alaska Power Authority for the Railbelt Intertie.
vi
TABLE OF CONTENTS
1 -INTRODUCTION 1
1.1 -Historical Literature Review 1
1.2 -Objectives 3
1.3 -Study Area 4
1.4 -Acknowledgments 4
2 -METHODS 8
2.1 -Selection and Configuration of Bird Census Plots 8
2.2 -Measurement of Habitat Variables 9
2.3 -Bird Censusing 12
2.4 -Waterbird Surveys 12
2.5 -Raptor Surveys 14
2.6 -Avifaunal Survey 16
2.7-Small Mammal Sampling 17
2.8 -Analytical Techniques . 19
3 -BIRDS -RESULTS AND DISCUSSION 23
3.1 -Habitat Descriptions of Census Plots 23
3.2 -Species Composition and Relative Abundance 40
3.3 -Breeding Bird Densities 40
3.4-Waterbird Use of Wetlands 48
3.5 -Breeding by Cliff-nesting Raptors, Ravens, and Eagles 58
3.6 -Avifauna/Habitat Relationships 65
3.7 -Annotated List of Species 76
vii
TABLE OF CONTENTS (Continued)
4 -NON-GAME (SMALL) MAf4MALS -RESULTS AND DISCUSSION
4.1 -Species Composition and Relative Abundance
4.2 -Small Mammal/Habitat Relationships
5 -ANTICIPATED IMPACTS
5.1-Watana Dam and Impoundment
5.2·-Devil Canyon Dam and Impoundment
5.3 -Borrow Areas
5.4 -Access Route
6 -LITERATURE CITED
viii
105
105
112
130
130
134
137
140
142
LIST OF TABLES
Table
1. Measured habitat variables used to describe bird and small
mammal intensive study plots, upper Susitna River Basin,
Alaska, July-August 1980-81 10
2. Summary of values of habitat variables from each 10-ha
intensive study plot, upper Susitna River Basin, July-
August 1980-81 26
3. Frequencies (%) of shrub and herb species in the ground
cover of intensive study plots, upper Susitna River Basin,
Alaska, July-August 1980-81 30
4. Relative abundance of loons, grebes, and waterfowl, upper
Susitna River Basin, Alaska 41
5. Relative abundance of large landbirds and cranes, upper
Susitna River Basin, Alaska 42
6. Relative abundance of shorebirds and gulls, upper Susitna
River Basin, Alaska 43
7. Relative abundance of small landbirds, upper Susitna River
Basin, Alaska 44
8. Avian habitat occupancy levels, upper Susitna River Basin,
Alaska, breeding season 1981 45
9. Number of territories of each bird species on each 10-
hectare census plot, upper Susitna River Basin, Alaska, 1981 46
10. Number of adult waterbirds (or independent youn~) and
broods found on 28 waterbodies (total = 20.5 km of
wetlands), upper Susitna River Basin, Alaska, July 1981 49.
11. Summary of total numbers-and species composition of water-
birds seen on surveyed waterbodies curing aerial surveys
of the upper Susitna River Basin, fall 1980 52
12. Summary of total numbers and species composition of water-
birds seen on surveyed waterbodies during aerial surveys
of the upper Susitna River Basin, fall 198 1 53
13. Summary of total numbers and species composition of water-
birds seen on surveyed waterbodies during aerial surveys
of the upper Susitna River Basin, spring 1981 54
ix
LIST OF TABLES
14. Seasonal population statistics for the more important of
surveyed waterbodies of the upper Susitna River Basin,
1980-81 56
15. Location of active raptor and raven nest sites, upper
Susitna River Basin, ~laska, 1980 and 1981, and their
proximity to potential adverse disturbance from construc-
tion activities 62
16. Breeding chronologies of eagles, Gyrfalcon, and Common
Raven in interior Alaska 66
17. General types of impacts to raptors (from Roseneau et al.
1981) 67
18. Factors that affect the sensitivity of raptors to dis-
turbances (from Roseneau et a 1. 1981) 68
19. Influence of timing of disturbance on the possible effects
on raptors (from Roseneau et al. 1981) 69
20. Linear distances of cliffs in vicinity of proposed
impoundments, and distances that would be inundated,
Susitna Hydroelectric Project 70
21. Number of known raptor or raven nest sites in upper
Susitna River Basin, Alaska, that would be inundated by
Devil Canyon and Watana reservoirs 71
22. Species of small mammals found in the upper Susitna
River Basin, Alaska, 1980 and 1981 106
23. Standardized habitat niche breadth values for ten small
mammal species sampled by snap and pitfall trapping at
43 sites, upper Susitna River Basin, fall 1981 120
24. Standardized habitat niche breadth values for six small
mammal species captured on 22 trapping sites during
three sampling periods, upper Susitna River Basin, 1980-81 122
25. Number of breeding territories of small-and medium-sized
upland birds that would be impacted through habitat
destruction or alteration as a result of the Susitna
Hydroelectric Project, Alaska 131
X
LIST OF FIGURES
Figure
1. Map of the upper Susitna River Basin, Alaska, showing
locations of the 12· bird census plots and the waterbodies
included in the waterfowl surveys. 5
2. Locations of small mammal trapline sites in the upper
Susitna River Basin, Alaska, 1980-81. 7
3. Relativ.e importance of 20 waterbodies for migrant loons,
grebes, and waterfowl in the upper Susitna River Basin,
Alaska, compared to 3 waterbodies in the upper Tanana
River-Scottie Creek area of eastern Alaska in fall 1980. 59
4. Relative importance of 34 waterbodies for migrant loons,
grebes, and waterfowl in the upper Susitna River Basin,
Alaska, in spring 1981 compared to 9 waterbodies in the·
upper Tanana River Valley of eastern Alaska in spring
1980. 60
5. Habitat ordination of 22 bird species in the upper Susitna
River Basin, Alaska, based on a three-dimensional plot of
mean factor scores from subplots on which the species
occurred at least once during 1981 censuses. 74
6. Temporal variation in numbers of small mammal captures
at 22 trapline sites in the upper Susitna River Basin,
Alaska, 1980-81. 108
7. Seasonal chronologies of the arctic ground squirrel,
Talkeetna Mountains near Anchorage, Alaska (after Hock
and Cottini 1966). 110
8. Clustering of 42 small mammal trapline sites into similar
vegetative groupings, based on an analysis of frequency
counts of 81 plant taxa in the ground cover. 113
9. Abundance of eight small mammal species relative to
vegetation types at 42 trapline sites in the upper Susitna
River Basin, Alaska, 29 July-30 August 1981. 115
10. Two-dimensional ordination of 43 small mammal trapline
sites trapped in fall 1981, upper Susitna River Basin, Alaska,
based on principal component analyses of ground-1 evel
structural habitat variables. The two principal components
accounted for 41% of total variance in measured variables
among sites. Vegetation types that correspond to the
groupings of mean factor score centroids are indicated. 116
xi
.LIST OF FIGURES (Continued)
11. Habitat occupancy patterns of small mammals captured at
43 trapline sites, upper Susitna River Basin, Alaska,
29 July-30 August 1981. Species relative abundance has
been added as a vertical axis to the two-dimensional PCA
ordination shown in Figure 10. 117
12. Two-dimensional ordination of 22 small mammal trapline
sites trapped during all three 1980-81 sampling periods,
upper Susitna River Basin, Alaska, based on principal
component analyses of ground-level structural habitat
variables. The two principal components accounted for
40% of total variance in measured variables among sites.
Vegetation types that correspond to the groupings of
mean factor score centroids are indicated. 124
13. Changes in habitat occupancy patterns of tundra voles and
meadow voles between fall 1980 and fall 1981, upper Susitna
River Basin, Alaska. Species relative abundance has been
added as a vertical axis to the two-dimensional PCA
ordination shown in Figure 12. · 125
xii
1 -INTRODUCTION
The bird and non-game or small mammal studies of the upper Susitna River
Basin were undertaken to aid in determining the potential effect that
the proposed Susitna Hydroelectric Project might have on the fauna of
the region. More specifically, we learned what species of birds and .
small mammals were present in the upper Susitna River Basin and, on a
seasonal basis, the manner and extent of their use of the region, in-
cluding the general habitats in which they occurred. These data, while
not definitive after only 1~ field seasons, can be used with care to
1) evaluate habitat potential in the area, 2) provide a basis for pre-
dicting faunal changes based on habitat changes caused by environmental
alterations, including changes in water level, and 3) evaluate possible
mitigative measures.
The bird and small mammal studies were composed of three interrelated
work packages: 1) Bird community-habitat study, 2) Avifaunal survey,
and 3) Small mammal studies. Field studies were conducted during the
following periods: 6 July-4 October 1980, 8-10 February 1981, and
17 April-23 October 1981.
1.1 -Historical Literature Review
Prior to the initiation of this study, almost nothing was known about
the birds and small (non-game) mammals of the upper Susitna River Basin.
The only published bird information from the region was a report of
birds seen by Hinckley (1900) while he was with a U.S. Geological Survey
party in the Susitna Valley in 1898. In the surrounding regions,
Abercrombie (1899) in summer and Bailey (1926) in winter both visited
the upper Copper River Basin and provided sketchy accounts of birds
I
seen. More recen"~.ly, Williamson and Peyton (1959) reported inland
breeding of Double-crested Cormorants (Phalacrocorax auritus) at Lake
Louise, and Schaller {1954) reported on summer birds seen in the
1
Talkeetna Mountains. More data were available from the vicinity of
Denali (Mt. McKinley) National Park, where 0. J. Murie (1923, 1924),
A. Murie (1946, 1956), Dixon (1927a, 1927b, 1933a, 1933b, 1933c, 1938),
and Sheldon (1909, 1930) spent extended periods of time~
A. Murie (1963) prepared a generalized summary of occurrence of birds in
Denali National Park, and a recent checklist of the birds of the Park
was compiled by Kertell (1981). In the Ala~ka Range, directly north of
the Susitna study area, a study of the nesting and hunting behavior of
the Gyrfalcon* has just been completed (Bente 1981). All pertinent
pre-1978 data from the above citations have been consolidated and sum-
marized by Gabrielson and Lincoln (1959) and Kessel and Gibson (1978).
Between 10 and 15 June 1974, White (1974) carried out a raptor survey on
the Susitna River upstream of the proposed Devil Canyon dam site; and,
between 12 and 15 July 1975 and on 18 July 1975, White and Cade (1975)
conducted a raptor survey on the proposed Susitna powerl ine corridors,
but not in the current study area.
The small mammals of the upper Susitna River Basin had never been sur-
veyed prior to this study and hence were essentially unknown except by
inference. ~.£ubl ished speci,es 1 ists for nearby areas of central Alaska
came from a small number of studies and surveys: Denali National Park
area (Sheldon 1930, Dixon 1938, Viereck 1959, A. Muri e 1962), several
collecting sites on the Denali and Richardson highways (Baker 1951,
Strecker et al .. 1952, Baker and Findley 1954, Pruitt 1968), and the ...
upper Cook Inlet area (Osgood 1901, Wilber 1946, Hocok and Cottini 1966).
General distributional information has been summarized by Manville and
Young (1965) and Hall (1980).
*See Annotated List of Species (Section 3.7) for scientific names of
birds, Table 22 for scientific names of small mammals.
2
Historically, little attention has been paid to bird and mammal species-
habitat relationships in Alaska, although generalized, descriptive
accounts of species habitats can be found scattered throughout the
literature.
1.2 -Objectives
Over the two-year period of this study, the general objectives of the
three work packages were as follows:
(a) Bird community-habitat study
(i) Determine, for as many of the major upland avian habi-
tats of the region as feasible, the type and degree of
use by birds, and compare these habitats relative to
species composition, density, etc.
(ii) Obtain data relative to species habitat use that can be
used in later analyses on habitat selection by specific
species (1982).
(b) Avifaunal survey
(i) Determine all species of birds using the region.
(ii) Determine, on a seasonal basis, each species' relative
abundance and general habitat use.
(iii) Determine spring and fall migration dates (earliest,
latest, peak) and, insofar as time permits, t~e seasonal
chronologies of each species.
3
(iv} Determine the extent and type of use of the area by the
Peregrine Falcon, Bald Eagle, and Osprey.
(v) Determine, generally, the use of the region by water-
birds, including shorebirds and waterfowl.
(c) Sma 11 (non-game) mamma 1 studies
(i) Determine all species of small, and medium-sized mammals
occurring in the region.
(ii) Determine, for the major vegetation types of the region,
species composition3 relative abundance, and habitat
use.
1. 3 -Study Area
Geographically; the overall study area extended from near Shennan,
adjacent to the Alaska Railroad, up the Susitna River to the mouth of
the MacLaren River, and out to approximately 15 km (10 miles) on either
side of the river. Survey work included habitats throughout this vast
area, but intensive work was located within a few kilometers of the
present river channel. Except for the Cottonwood Forest plot at
Sherman, the intensive sites are located between the Devil Canyon dam
site and the southeast-facing slopes east of Kosina Creek (Fig. 1 and
2).
1.4 -Acknowledgments
A: project of the scope of these bird and small mammal studies could not
be conducted without the assistance of many competent field and labora-
tory personnel, and we are pleased to acknowledge and express apprecia-
tion for all such help we have received. Kevin C. Cooper partfcipated
4
FIGURE 1
Map of the upper Susitna River Basin, Alaska, showing locations of the 12 bird census plots ( ~ )
and the waterbodies (numbers) included in the waterfowl surveys.
Ot::==5--lllli1EO===:J15 KILOMETERS
FIGURE 1 (Continued)
SCALE
............ I
0 S 10 IS 20 MILES
0 5 10 20 30 KILOMETERS
FIGURE 2
,--..~ .............. __ ,_J\.,/
-.J
-..... ,~-'1., --.... ,
I
I
(
...
I
I
' ,,
\.."\
\ ....
' \
I
I
I
\..._,...._
Locations of small mammal trapline sites in the upper Susitna River Basin,
Alaska, 1980-81.
in all field aspects of the study during 1981 and shouldered the major respon-
sibilities for all the 1981 waterfowl surveys. Alan M. Springer in 1980 and
David G. Roseneau in 1981 shared their raptor-hunting expertise with us by
participating in aerial raptor surveys. Brian E. Lawhead, in 1980, helped
monitor fall bird migration and flew all of the fall waterfowl surveys. A
number of other field assistants also made significant contributions to our data-.
gathering efforts, including Susan R. Lucachick, Michael K. MacDonald, Donald A.
Williamson, Jan Overturf, and Maurice L. Ward. Edward C. Murphy and Douglas P.
Pengilly provided statistical advice and assistance, and Catherine H. Curby
compiled and manipulated all of our massive habitat and animal computer data files.
We also appreciated all the contributions made to our studies by various members
of the Furbearer study group: PhilipS. Gipson, Steven W. Buskirk, T. Winston
Hobgood, David P. Volsen, William H. Busher, and Richard F. Morse. We thank
John Ireland, resident at Murder Lake, for his hospitality and for sharing his
many bird observations with us. And we laud the fine logistics provided by all
the field support personnel at Watana and High Lake, especially Onnalie Logsdon
of Terrestrial Environmental Specialists and the helicopter pilots from ERA
Helicopters, Akland Air, and Air Logistics.
Our studies were conducted under a contract between the University of Alaska
and Terrestrial Environmental Specialists, Inc., for Acres American, Inc., and
the Alaska Power Authority.
2 -METHODS
2.1 -Selection and Configuration of Bird Census Plots
Twelve square 10 ha (25 acres) bird census plots were established in the
' study area. This plot size is above the minimum recommended by the Inter-
national Bird Census Committee (1970) and is one thl,t can be adequately
censused in 4 h, the approximate period of maximum bird activity each
morning. Except for the Alpine Tundra plot, sites were selected in
relatively uniform patches of vegetation that represented each of the
8
major woody avian habitats (after Kessel 1979) present in the region.
The Alpine Tundra plot was selected to include several of the widespread
avian habitats found at the higher elevations of the study area. Each
of the 10-ha plots was divided by a 7 x 7 grid to aid in animal census-
ing procedures and in an~lysis of habitat variables.
2.2 -Measurement of Habitat Variables
The variables chosen to describe the habitats (Table 1) \'/ere those
judged most likely to affect, either directly or indirectly, the animal
community structure, species composition, and habitat occupancy levels
of these habitats. Some of these variables had already been tested in
central Alaska by Spindler (1976), Wolff (1977), West (1979), MacDonald
(1980), and Spindler and Kessel (1980).
The gridded subplots and small mammal trap stations were used as sample
units in vegetation analyses. Systematically located points were
sampled, using the point-centered quarter method of Cottam and Curtis
(1956), but including more detailed sampling of ground cover, under-
story, and shrub vegetation. Sampling was vertically stratified into
six layers (after Kessel 1979): ground cover (<0.25 m), dwarf shrub
(<0.4 m), low shrub (0.4-1.1 m), medium shrub (1.2-2.4 m), tall shrub
(2.5-4.9 m), and tree (~5.0 m).
Non-vegetative variables measured included litter depth, microrelief,
distance to nearest standing water, if any, in subplot, and character~
istics of that water (fluviatile or lacustrine, depth, surface area),
distance to habitat edge and the length of that edge if any, in a sub-
plot, and the slope and aspect of the 10-ha study plot (Table 1). Age
of stands was determined by taking 10-20 auger core samples from the
largest trees on a plot, or, in the case of the tall shrub plot, by
cutting the largest stems from alder shrubs and counting the growth
rings.
9
TABLE 1
MEASURED HABITAT VARIABLES USED TO DESCRIBE BIRD AND St1ALL MAM~1AL INTENSIVE STUDY PLOTS, UPPER
SUSITNA RIVER BASil!, ALASKA, JULY-AUGUST 1980-81.
Habitat Variable
Distance between trees
Distance between shrubs/shrub clumps*
Canopy area of shrub/shrub clump· .
Height of trees and shrubs
Diameter of tree trunk
Canopy thickness of tree layer and shrub
layer
Foliage height density profile
Canopy coverage
Ground cover
Species frequency in ground cover
Dwarf shrub cover
low shrub cover
Tree and shrub importance values
litter depth
Microrelief
Distance to water
f>lethod
A~erage distance to nearest tree ·{~5 m height), in
quarters (Cottam and Curtis 1956)
Average distance to center of nearest shrub/shrub clump
(1.2-4.9 m high), in quarters (Cottam and Curtis 1955)
Average area of shrub/shrub clump canopy, in quarters
(Cottam and Curtis 1956). Calculated as area of ellipse
from length and width measurements)
Average height of nearest tree and nearest shrub, in
quarters (Cottam and Curtis 1956}
Average diameter (dbh) of trunk of nearest tree, in
quarters (Cottam and Curtis 1956)
A~erage canopy thickness of nearest tree and nearest
shrub, in quarters (Cottam and Curtis 1956}. Derived
from distance between lowest live branch and top of
tree or shrub.
Average number of 64 5.0 x 5.0 em coverboard squares
contacted, 3 m from centerpoint in quarters (Cottam
and Curtis 1956), at heights 0-0.4 m, 0.6-1.0 m,
1.6-2.0 m, 3.5-3.9 m
Percent of 20 sightings (10 at 1 m intervals
along each of two perpendicular lines centered on
centerpoint) showing vegetation contact at cross-hairs
of a vertical ocular tube. Tree and shrub as well as
total canopy coverage obtained.
Percent each of sedge, grass, forb, microshrub
(<0.25 m), litter, moss, lichen, water, and bare soil
in a 1.0 x 1.0 m plot with corner on centerpoint.
Occurrence of specific plant species in the 1.0 x 1.0 m
plot at small mammal trap stations.
Percent of shrub cover <0.4 m high in 3.0 x 3.0 m plot
with corner on centerpoint.
Percent of shrub cover 0.4•1.1 m high in the 3.0 x 3.0 m
plot.
Sum of relative frequency, relative density, and
relative dominance of species, nearest tree and
nearest shrub species in quarters (Curtis and
Mcintosh 1951)
Average depth of.five random samples in the 1.0 x 1.0 m
plot, using calibrated probe
Maximum vertical range of topography in the 3.0 x 3.0 m
plot
Distance to nearest perennial water, if any, on subplot
from' centerpoint
10
TABLE 1 (Continued)
Habitat Variable
Size and type of waterbody
Depth of waterbody
Distance to habitat edge
Length of habitat edge
Slope
Aspect
Age of stand
Method
Area and edge of waterbody within a subplot, calculated
as area and circumference of an ellipse, respectively,
from length and width measurements. Type differentiated
as lacustrine or fluviatile
r~aximum depth of water
Distance to nearest edge, if any, on subplot from
centerpoint. Defined as edge of forest opening at
least 30 m x 30 m, or edge of shrub thicket opening
at least 15 m x 15 m.
Length of edge within a subplot
Degree of slope of 10-ha plot as measured with Abney
1 evel
Direction of slope exposure of 1D-ha plot measured
with a compass
Number of growth rings obtained from cut stems or-·
with tree auger
*Clumps of intertwining shrubs were treated as a single shrub for the purpose~ of habitat analyses
11
2.3 -Bird Censusing
A modification of the territory mapping census method (International
Bird Census Committee 1970) was used to determine the densities of
breeding birds on each of the twelve 10-ha bird census plots. The 7 x 7
gridding of each plot resulted in forty-nine 0.2-ha subplots, which were
used in censusing and in the subsequent plotting of territories and
analyses of avian-habitat relationships. In all, 588 subplots were
censused in 1981.
Three field parties conducted a total of eight censuses on each 10-ha
plot between 20 May and 3 July 1981. Each census took approximately
4 h, usually between 03:00 and 08:00 (Alaska Standard Time), which is
generally within the time of greatest singing activity. Censuses were
conducted in pairs of two consecutive days at each plot, partly to
minimize the effects of changing territorial boundaries and partly to
alleviate transportation problems between plots. During a census, the
observer stopped at the center of each subplot for 2-7 minutes, depend-
ing upon avian activity, and recorded on a field map of the plot all
birds seen or heard. For birds seen, sex and age, activity, spatial
location (height above ground and positioning within a shrub or tree),
and substrate used (including plant species) were also recorded.
2.4 -Waterbird Surveys
Data on the use of wetlands by waterbirds were obtained primarily from
two types of surveys of the lacustrine waterbodies of the region:
ground censuses during the breeding season and aerial surveys during . . .
migration. Generally, we examined most of the large lakes near the
proposed impoundments, plus a number of smaller lakes and ponds that
were near proposed aco:ss routes or that were efficiently exar.1ined
because they were either near the large lakes or were located on the
route between two of the 1 arger 1 akes.
12
Ground censuses of 28 waterbodies, involving 53 party-hours of field
work, were conducted between 8 and 29 July 1981. Each waterbody was
censused once. A census consisted of two or more people either walking
around the shoreline of a waterbody or paddling the edges in an inflat-
able Sea Eagle canoe, or sometimes both simultaneously, and enumerating
all waterbirds and broods present. The efficacy of this method of
censusing individual waterbodies and its usefulness for comparing water-
bird population characteristics over time and for detennining the rela-
tive importance of different waterbodies to waterbirds is discussed by
Spindler et al. (1981).
Aerial surveys to monitor waterbody use during migration were also based
on counts from individual waterbodies. Surveys were conducted 7 September-
4 October 1980, 3-26 May 1981, and 15 September-23 October 1981. We
began aerial surveys earlier and conducted more of them in fall 1980
than in 1981, because it was necessary to familiarize ourselves with the
use patterns in the region during the first year. In fall 1981 the
surveys were not as extensive or intensive. We began them later in
September, but continued them until most of the waterbodies were frozen.
We tried to time our first survey in 1981 to catch the peak of waterfowl
migration, but apparently missed it because of a somewhat earlier move-
ment of wigeon, Pintail, and scaup in 1981. The pattern of migration
and waterbody use during both fall periods was similar, however.
An average of 34 waterbodies was included in each survey, but the number
varied as we developed our sampling scheme and in response to 100% ice
cover. Brian E. Lawhead flew all the surveys during fall 1980, and
Kevin C. Cooper flew them all during 1981. All but the 3 October 1980
survey were made from a Bell 2068 "Jet Ranger" helicopter, with the
observer seated in the left front seat beside the pilot. The other
survey was made in an Aerospatiale AS350 "A· Star.••
13
In searching for birds, usually a single pass was made over small water-
bodies. With larger waterbodies, the helicopter followed the shoreline,
usually in a counterclockwise direction so that the observer was on the
water side. Diving ducks in particular were less disturbed when the
helicopter flew over the shore instead of over water. Large lakes
containing scattered birds were surveyed in sections. Flights during
counts were at about 80 km/h (50 mph) and between 30 and 75 m (100-
250 ft) above ground level. When flocks of birds were encountered, the
helicopter circled widely and slowly around the birds while the observer
counted~and identified them, sometimes with the aid of 7X,35 binoculars.
Hovering or circling directly over waterfowl was avoided, because it
unnecessarily disturbed the birds, causing them to scatter and dive and
making enumeration difficult.
As with most aerial surveying, accuracy of results was subject to many
foibles, including weather-caused factors (sun glare, choppy water), bird
behavior (diving, flushing, hiding in vegetation), differences in heli-
copter performance and pilots 1 flying styles, etc. Generally, however,
we feel that results were a reasonably accurate indication of the
species and numbers present on the respective waterbodies at the time of
the surveys.
2.5 -Raptor Surveys
Information on use of the ·region by breeding raptors and ravens was
derived from 1) helicopter surveys on 6 July 1980 and 16 and 17 May 1981
of all cliff habitat along the Susitna River ~nd its tributaries (but
not the up 1 and c 1 iffs and tors), from Portage ( 1980) and Indian (1981)
creeks to the mouth of the Tyone River, and, on 3 and 5 July 1981, of
habitats along the proposed access routes, 2) ground visits to all 1980
and 1981 active nest sites, 3) special ground and aerial searches of
vegetated cliff habitat (potential Peregrine habitat?), 4) supplemental
observations made whenever flying over or working near raptor habitat,
and 5) from miscellaneous observations made throughout the study period.
14
Aerial surveys of raptor cliff-nesting habitat were conducted from Bell
206B "Jet Ranger 11 helicopters. Three observers in addition to the pilot
took part in each survey. Brian A. Cooper participated in all surveys;
he was accompanied in July 1980 by A. M. Springer and 0. Logsdon, in May
1981 by D. G. Roseneau and K. C. Cooper, and in July 1981 by K. C.
Cooper .and S. R. Lucachick. Because of the ability and accumulated
experience of the observers, we feel that our surveys were as accurate
as most aerial surveys of this type.
Dur{ng the surveys, the helicopter moved slowly past cliff faces as
close as the pilot deemed safe, usually at a distance of about 30-40 m.
When necessary for better observation, the helicopter hovered for short
periods or made more than one pass past a site. All active and inactive
nest sites were recorded and briefly described on 1:63,000 USGS quad-
rangle maps. All nest sites found in earlier surveys, including those
by White (1974), were relocated and checked for activity.
Between 20 May and 13 July 1981, we visited all 1980 and 1981 active
cliff sites from the ground, taking photographs of each site and record-
ing data on nest site characteristics and cliff habitat in proximity of
each site (data on fi-le at University of Alaska Museum). Several times
. during early summer and at least once from the ground in June 1981, we
examined all potential Peregrine-type habitat (vegetated cliffs). In
all, some 44 party-hours were spent in these ground examinations of
raptor habitat.
Over the course of the summer, we roughly delineated all cliffs in or
near the impoundment area on 1:63,000 USGS quadrangle maps and classi-
fied cliffs according to their structure and apparent quality for nest
sites. "A" cliff habitat·had cliffs large enough to support a nest, had
ledges and nooks for nest placement, and had little loose material; 11 811
cliffs had these same attributes, but were smaller and perhaps not large
15
enough to support a nest; and "C" cliffs had loose substrates (dirt and
rock banks or loose talus) and probably would not have been used by
rap tors.
2.6 -Avifaunal Survey
In addition to data gathered during the intensive activities described
above, we accumulated general data on the avifauna through several other
means:
(a) A daily checklist enumerating all independent individuals (as
opposed to dependent broods) of all species observed was
maintained while we were in stationary camps.
{b) Whenever time permitted, we walked cross-country at various
locations throughout the upper basin, recording all indivi-
duals of all species seen and, whenever feasible, the habitats
utilized. Hours in the field and distance traveled were
recorded, broken down by habitat when possible. In all, over
630 party-hours were spent in this form of survey.
(c) All observations related to breeding chronologies were re-
corded, e.g., nests and their contents, and age and activity
of dependent broods.
(d) Observations were solicited, either verbally or through posted
data sheets, from others working in the region.
16
2.7-Small Mammal Sampling
(a) Shrews and Voles
To sample shrew and vole populations, we used a modification of the
North American Census of Small Mammals (Calhoun 1948). Trapline_ tran-
sects consisted of 20 trap stations, spaced every 15.2 m. T\'IO 11 Museum
Special 11 snap-traps and one pitfall trap (primarily for shrews) were set
within a 1-m radius of each trap station centerpoint for three consecu-
tive nights. Snap-traps were baited with a mixture of peanut butter,
rolled oats, and ground walnuts or sunflower seeds. Pitfalls, which
were heavy galvanized sheetmetal cones measuring 155 mm in diameter and
260 mm in depth, were pressed into the ground so that the cone opening
was flush or slightly lower than ground level; they were not baited.
Two trapline transects, treated as independent samples in analyses, were
set up along grid lines number three and five of each 10-ha bird census
plot (except on the multihabitat Alpine Tundra plot). In addition, we
established a number of traplines at other locations in the study area,
on vegetationally-homogeneous sites that represented the wide range of
vegetation types present in the upper Susitna River Basin. By fall
1981, the number of trapline transects in operation totaled 49.
During each sampling period we recorded the following data for each
animal trapped: date, location, trap type (snap-trap or pitfall),
species, sex, weight (using 10 g, 50 g, and 100 g Pesola scales), and
reproductive condition (males--testes abdominal or scrotal; females--
pregnant, number and size of embryos, lactating). Representative
samples of study skins and skeletal material were preserved and
deposited in the University of Alaska Museum.
17
(b) pther Small Mammals
Systematic enumeration of small mammals other than shrews and voles
proved to be impractical, largely because each species required a dif-
ferent, time-consuming census technique, the application of which was
impossible within time and manpower constraints. Also, some of these
other small mammals, while common and widespread throughout central
Alaska, were present in relatively low densities in the upper Susitna
River Basin (snowshoe hare and porcupine) or were in locations unlikely
to be impacted by activities related· to the Susitna Hydroelectric
Project (collared pika and hoary marmot).
Attempts to census ground squirre1s in 1981 failed, largely because of
.inconsistencies among inexperienced observers in the recording of
squirrel sign and habitat variables. With four observers, we conducted
transect cEmsuses at eight fox den sites and 20 non-fox den sites above
treeline between 9 August and 17 September 1981. Each census consisted
of an obset·ver walking a north-south transect and then an adjoining
east-west transect, each 500 paces long (approx. 365m), and stopping to
record at E!very 20 paces (approx. 15 m) the number of ground squirrel
burrow holes encompassed by a 2 m-radius circle centered at the
recorder's feet. Also recorded at each stop were vegetation type, slope,
aspect, and one of three substrate moisture categories--\"let, moist, dry.
In addition, the number of squirrel calls heard during a census was
ta1lied.
Red Squirrel counts are still to be made. These will be done in con-
junction with bird censusing in 1982, when observers will map active
squirrel middens on the bird census plots. Densities will be determined
by assuming one squirrel per midden (after Wolff and Zasada 1975).
Lacking more concrete data, relative abundance information given in
discussions below on these other sma.ll mammals is based on general
18
survey infonnation gathered by our field parties and from observations
contributed by others.
2.8-Analytical Techniques
(a) Jmportance Values
In an attempt to identify the waterbodies most significant to waterbirds
( 1 cons, gr1ebes, and waterfowl), we derived a relative n Importance Val uen
for each s1eason for each waterbody surveyed, i.e., we calculated an
Importance Value of a waterbody.to breeding waterbirds compared to all
others surveyed during July 1981 (a total of 28 waterbodies), another
for 20 wat1erbodies surveyed during fall 1980, and another for 34 water-
bodies surveyed during spring 1981. The importance value of each water-
body at a given season was the sum of relative mean abundance (number of
birds) from the several censuses, the relative mean density (birds/km 2),
and the relative mean species richness (number of species) (after Curtis
and Mcintosh 1951):
IMPORTANCE VALUE of
a 111a terbody
mean density of birds
per census on waterbody
sum of mean densities of
birds per census on all
waterbodies
=
+
19
mean number of birds
per census on waterbody
sum of mean number of
birds per census on all
waterbodies
mean number of species
per census on waterbody
sum of number of species
per census on all
wa terbodi es
+
(b) Avian Communities
The avian communities in the major terrestrial habitats of the region,
represented by the 12 bird census plots, were compared relative to
species composition, species richness (number of species), breeding
density, breeding biomass, and species diversity (H').
Breeding density was determined by estimating the number of territories
of each species, based on repeated observations of territorial males,
females, or breeding pairs (International Bird Census Committee 1970).
Partial territories were also determined and added to the number of
whole territories. Species that had only a small fraction of a terri-
tory on a plot were given a "+,11 which was counted as 0.1 territory in
calculations of breeding density, species diversity, and breeding bio-
mass. The breeding densities of early season nesters, such as Gray Jay
and chickadees, were estimated, based on repeated observations of adults
or immatur1es on the plot.
Species diversity was calculated using the diversity index, H' (Pielou
1975). Sp1ecies diversity has two components: number of species
(s·pecies richness) and the evenness (species equitability) with which
the individuals of the community are apportioned among these species
(Pielou 1975). H' reaches its maximum value in communities with many
species of nearly equal abundance. A community with many species dis-
tributed evenly may have the same diversity index as a community with
fewer species that are distributed evenly.
Breeding b'iomass was calculated for each plot as the sum of breeding
biomass fo1r each species breeding on the plot. Breeding biomass for
each species was calculated as the product of the density of breeding
birds and average weight of the species. Species weights used were an
average weight for all adult specimens in the University of Alaska
Museum that had been collected in Alaska during the breeding season. If
20
the sample size in the museum was too small, or variability too high, we
consulted published literature (Carbyn 1971, West and DeWolfe 1974) for
values determined from northern populations. Large-bodied breeding
birds, such as grouse or ptarmigan, were omitted from biomass calcula-
tions, because they tended to skew the total biomass disproportionately.
Breeding biomass was expressed as grams.breeding birds per 10 ha.
(c) Statistical Procedures and Data Presentation
.
Two procedures were used to organize the small mammal trapline sites
into groups, based on their similarities: cluster analysis and princi-
pal component analysis (PCA). Variables used in the analyses were our
measurements of ground-level habitat structure and plant taxa frequen-
cies, thus emphasiz·ing the stratum used by smallmammals and allowing
expression of variation among sites. The resultant groups of trapline
sites corresponded to vegetation types (see Section 4.2), which were
used to document patterns of small mammal habitat distribution, abun-
dance, and coexistence.
The cluster analysis (Biomedical Computer Program BMDP2M: Chi-Square
Procedure [Dixon and Brown 1979]) was performed using the plant taxa
frequencies. ·This technique is a method for organizing a data array,
based on a measure of similarity among variables, into groups or
clusters that are more similar within groups than among groups. In this
instance, trapline sites with the most similar composition of plant taxa
were clustered first (subgroups), and those less similar clustered
progressively later (major groups).
The principal component analysis (Biomedical Computer Program BMDP4M
[Dixon and Brown 1979]) was performed using measured structural habitat
variables. PCA is a statistical technique that reduces multivariate
data into at few dimensions, uncorrelated with each other, that are
linear combinations {"principal components") of the original variables
21
(Morrison 1976). The first new composite set of linear variables (PC I)
accounts for more of the variance (information) in the data set than any
other linear combination and thus provides the best summary of linear
relationsh·ips exhibited in the data. PC II accounts for the most
variance in the data set not accounted for by PC I, and each successive
component or dimension accounts for successi~ely less variance. From
our PCA analysis of habitat variables, we used PC I and PC II as axes on
which to ordinate the trapline sites (using mean factor scores), in
order to eJ,amine their interrelationships and to provide a base from
which to look at habitat occupancy patterns.
A PCA, based on measured habitat variables, was also used to ordinate
the breeding distribution of bird species relative to habitat character-
istics. A mean PCA factor score from all subplots on which a given
species was recorded at least once during censuses was calculated for
species that occurred on 10 or more subplots. These scores were plotted
on a three-dimensional diagram, using the first three principal com-
ponents of habitat characteristics as axes.
Distribution patterns of small mammals relative to groupings of vegeta-
tion types were further shown through the use of a three-dimensional
display technique (Surface II Graphics System Programs [Sampson 1978]).
The percentage of total number of captures of a given small mammal
species per trapping site was added as a vertical axis to the two-
dimensional PCA ordination of trapline sites. Block or "fishnet"
diagrams of each species, created by connecting contours of equal abun-
dance, give three-dimensional illustrations of a species' distributional
11 topography."
22
To quantify the variation in range of habitat use by small mammals, we
calculated values for habitat niche breadth for each species, using the
formula (after Krebs and Wingate 1976)
1
B =
where B=habitat niche breadth and p. = proportion of species total 1
density at trapline site i; p is defined from average density estimates:
d.
1
p. = 1
!:d.
1
where di =number of individuals per 100 trap nights at trapline site i.
Habitat niche breadth was then standardized by dividing by the total
number of sites.
3 -BIRDS -RESULTS AND DISCUSSION
3.1 -Habitat Descriptions of Census Plots
. .
Twelve intensive study plots were established in the shrub and forest
vegetation types of .the upper Susitna River Basin (Fig. 1). Plot sites
within these vegetation types were chosen to represent each of the major
woody avian habitats (Kessel 1979) present in the region in sufficient
size and uniformity to accommodate a square 10-ha (25-acre) study plot.
Below, in capital letters, are listed the avian habitats represented by
our plots, followed in parentheses by their most distinguishing habitat
characteristics and in bracltsts by the approximate vegetative equiva-
lents of Viereck and Dyrness (1980). Classified thereunder are the
twelve bird census plots.
23
DWARF SHRUB MAT (<0.4 m high), DWARF SHRUB MEADOW, AND BLOCK-FIELD
[Mat and Cushion Tundra, Mesic Sedge-grass]
Alpine Tundra
LOW (0.4-1.1 m high) AND/OR MEDIUM (1.2-2.4 m high) SHRUB THICKETS.
[Low and/or Tall Shrubland, separated at 1.5 m]
Dwarf-Low Birch Shrub Thicket
~1edium Birch Shrub Thicket
Low-Medium Willow Shrub Thicket
TALL (2.5-4.9 m high) SHRUB THICKET [Ta11 Shrubland, >1.5 m]
Tall Alder Thicket
DECIDUOUS (90% of canopy) FOREST [Deciduous Forest, 75% of canopy]
Cottonwood Forest
Paper Birct. Forest
MIXED (10-90% of Canopy) DECIDUOUS-CONIFEROUS FOREST [Mixed Conifer
and Deciduous Forest, 25-75% of canopy]
White Spruce-Paper Birch Forest I
~lhite Spruce-Paper Birch Forest II
CONIFEROUS (90% of Canopy} FOREST [Conifer Forest, 75% of canopy]
White Spruce Forest
24
SCATTERED WOODLAND (25 m high) AND DWARF FOREST (<5 m high)
(Stunted growth of 0.2-20% canopy)
[Conifer and Deciduous Woodlands,
10-24% tree canopy]
~lhi te Spruce Scattered Woodland
Black Spruce Dwarf Forest
There are two problems in the upper Susitna River Basin studies in using
the vegetative classification of Viereck and Dyrness {1980) to describe
a vi an habitats. One is the fact that their Tall Shrubl and supports t'I'IO
more or less distinct bird communities (medium and tall shrub birds of
Kessel [1979]). The other is that their definition of coniferous and
deciduous forests is not restricted enough for birds, since only about
10% of either vegetation type will attract the respective bird species
into these forests.
A brief description of each of the 10-ha study plots is provided below.
Table 2 presents a summary of the various habitat variables measured on
each of the 10-ha plots, and Table 3 gives the frequencies of shrub and
herb species in the ground cover of these plots. Generally, we have
used common names for the most important tree and shrub species
{Table 2) and major plant groups {e.g., sedges, lichens), but only
scientific names for the less common species and ground cover plants.
Nomenclatur·e follows Hulten (1968}, except for willows, which fo11ow
Argus ( 197:1) •
(a) ~lpine Tundra
The Alpine Tundra plot contained three distinct avian habitats, all
typical of and widespread in the high country of the region: Dwarf
Shrub r4ead()W, Dwarf Shrub Mat, and Block-field (rock scree). Vegetation
was all less than 0.4 m high, mostly less than 0.25 m. The Dwarf Shrub
25 ALftSfG~
TABLE 2
SUMMARY OF VALUES OF HABITAT VARIABLES FROM EACH 10-HA INTENSIVE STUDY PLOT, UPPER SUSITNA RIVER BASIN, JULY-AUGUST 1980-81. SEE TABLE 1 FOR
DESCRIPTION OF METHODS.
Dwarf-low Medium Low-Medium Tall White Spruce-White Spruce-White Black
Birch Birch Willow Alder Paper · Paper Paper Wh1te Spruce Spruce
Alpfne Shrub Shrub Shrub Shrub Cottonwood Birch Birch Birch Spruce Scattered Dwarf
Habitat variable Tundra Thicket Thicket Thicket Thicket Forest Forest Forest I Forest II Forest ~loodl and Forest
GROUND COVER (%)
Grass 3.4 22.0 4.1 16.0 21.1 19.3 12.5 28.7 8.2 2.5 4.8 3.4
Sedge 34.6 3.3 7.3 37.7 0.1 0.7 0.0 0.0 0.7 0.0 1.0 8.9
Forb 3.5 . 3.0 0.7 35.2 15.4 45.8 30.0 40.2 43.7 1.9 2.7 11.7
Microshrub (<0.25 m) 47.7 49.9 57.7 34.6 16.0 0.8 32.2 26.3 55.9 47.2 79.5 54.0
Utter 9.9 4.3 4.7 39.6 81.8 97.5 88.3 73.3 57.4 5.3 5.5 3.1
Moss 34.5 53.4 85.7 59.4 9,6 4.1 13.8 17.0 41.8 82.5 74.3 79.2
lichen 41.9 47.3 9.8 0.0 0.2 0.0 0.6 0.5 0.4 25.7 3.1 9,6
Water 3.0 0.0 0.8 4.4 0.0 0.0 0.0 0.0 0.0 o.o 0.3 1.9
Bare soil 16.3 2.3 1.1 0.0 6.4· 9.4 6.2 7.7 o.o 0.1 0.2 1.1
N MICRORELIEF (m) 0.23 0.27 0.37 0.25 0.13 0.22 0.32 0,28 0.30 0.24 0.32 0.33 c::n
LITTER DEPTH (em) 0.05 0.04 0.9 7.8 8.6 10.6 10.5 9.5 4.7 0.4 0.9 7.0
DWARF SIIRUB COVER ( <0. 4 m) (%) 53.4 54.0 61.8 44.4 27.7 1.7 38.4 7.5 58.2 60.6 81.5 64.3
LOW SfiRU8 COVER (0.4-1.1 m) (%) 0.0 28.2 22.3 47.7 19.9 28.1 3.9 33.4 12.0 19.8 34.0 34.5
MEDIUM-TALL SfiRU8S/SfiRUB CLUMPS
(1.2-4.9 m)
Distance between shrubs (m) ( 1.1)* 1.5 4.6 3.6 1.4 5.1 2.7 3.7 5.9 2.0 2.5
Shrub height (m) (0.5) 1.4 1.3 3.8 2.6 3.7 3.2 2.4 2.8 1.5 2.9
Height to canopy bottom (m) 0.1 0.3 0.2 0.6 0.2 0.1 0.4 0.2 0.2 0.2
Canopy thickness (m) 1.3 1.1 3.6 2.0 3.5 3.1 2.0 2.6 1.4 2.7
Canopy area (m 2 horizontal
plane) 1.3 0.9 12.3 2.6 8.3 7.5 1.8 0.9 1.8 1.4
Shrub heterogeneity (100 SD/x) --(61.4) 37.1 101.3 47.8 29.4 45.4 50.0 39.1 56.1 50.1 60.2
TABlE ·2 (Continued)
Dwarf-low Medium low-Medium Tall White Spruce-Whlte Spruce-White Black
Birch 81 rch 1/illow Alder Paper Paper Paper White Spruce Spruce
Alpine Shrub Shrub Shrub Shrub Cottonwood Birch Birch Birch • Spruce Scattered Dwarf
Habitat variable Tundra Thicket Thicket Thicket Thicket Forest Forest Forest 1 Forest II Forest Woodland Forest
TREES (~5.0 m)
Distance between trees (m) 6.2 5.6 8.0 3.8 4.6 20.6
Tree height (m) 17.6 13.5 13.5 12.9 10.4 9.0
Height to canopy bottom (m) 7.4 4.2 1.3 1.5 0.6 0.1
Canopy thickness (m) 10.1 9.3 12.2 11.4 9.8 8.9 --
Tree diameter (m dbh) 0.34 0.21 0.23 0.18 0.16 0.22
Tree heterogeneity (100 SD/x) 54.0 57.7 30.3 29.4 34.0 44.4
CANOPY COVERAGE (%)
Trees 0.0 0.0 0.0 0.0 0.0 56.5 55.0 25.5 57.5 19.5 3.0 1.5
Nedfum-tall shrubs 0.0 0.0 18.0 5.0 74.5 70.0 30.0 64.5 9.5 3.5 14.5 15.0
N Total (trees & sh~ubs) 0.0 0.0 18.0 5.0 74.5 87.5 74.0 79.5 62.5 21.5 17.5 16.5 .....
FOLIAGE DENSITY PROFILE (number
of coverboard squares contacted)
Woody sterns:
0.0-0.4 m 5.6 44.7 62.3 57.8 46.1 53.0 35;7 43.1 38.5 53.2 59.8 54.1
0.6-1.0 m 0.0 5.3 58.0 40.0 34.0 47.7 27.0 38.7 16.5 20.9 51.5 29.6
1.6-2.0 m o.o o.o 2.7 0.0 44.1 37 .o 27.0 42.9 16.9 15.0 8.7 15.3
3.5-3.9 m o.o 0.0 0.1 0.0 40.5 42.3 29.4 36.1 21.3 15.5 2.5 7.7
Graminoid stems:
0.0-0.4 m 10.0 18.9 12.1 40.1 33.1 41.0 42.5 50.3 25.5 6.2 12.1 16.7
0.6-1.0 m 0.0 0.2 1.7 7.2 7.2 13.5 14.5 18.6 2.8 0.3 1.0 0.7
1.6-2.0 m 0.0 0.0 o.o o.o 0.0 0.1 0.9 0.3 0.3 0.0 0.0 0.2
TABLE 2 (Continued)
Dwarf-Low Medium Low-Medium Tall White Spruce-White Spruce-White Black
Birch Birch W1llow Alder Paper Paper Paper White Spruce Spruce
Alp1ne Shrub Shrub Shrub Shrub Cottonwood Birch Birch Birch Spruce Scattered D~1arf
Habitat variable Tundra Th1cket Thicket Th1cket Thicket Forest Forest Forest I Forest II Forest Woodland Forest
Forb stems:
0.0-0.4 m 0.6 1.1 0.4 20.2 22.7 42.4 24.7 33.4 24.9 3.4 5.3 10.5
0.6-1.0 m 0.0 0.~ 0.0 0.0 1.0 16.8 5.2 3.0 2.4 0.0 0.0 0.1
1.6-2.0 m 0.0 o~q 0.0 o.o 0.0 0.2 0.3 0.0 o.o o.o o.o 0.0
TREE IMPORTANCE VALUES
White spruce, Picea glauca 0 0 0 0 0 15 61 163 129 202 293 0
Black spruce, Picea mariana 0 0 0 0 0 0 0 0 2 90 7 0
Cottonwood, Populus
bal samHera 0 0 0 0 0 220 0 0 0 2 0 0
Quaking aspen, Populus
N tremuloides 0 0 0 0 0 0 9 0 0 0 0 0
co Willow, Sa11x spp. 0 0 0 0 0 1 0 0 0 4 0 0
Paper birch, Betula
papyrifera 0 0 0 0 0 2 223 135 169 2 0 0
Alder, Alnus spp. 0 0 0 0 0 62 7 2 0 0 0 0
MEDIUM-TALL SHRUB IMPORTANCE
VALUES
UhHe spruce, Picea glauca 0 0 0 0 0 0 37 18 91 118 0 8
Black spruce, Pfcea mariana 0 0 0 0 0 0 0 0 2 141 4 284
~lfllow, Salix spp. 0 0 0 124 5 13 5 0 14 2 3 8
Shrub birch, Betula
glandulosa/hybrids 0 0 300 164 5 0 0 0 0 13 289 0
Paper birch, Betula
paPYrifera 0 0 0 0 0. 0 30 37 54 13 0 0
Alder, Alnus spp. 0 0 0 12 289 195 211 240 95 13 4 0
Raspberry, Rubus idaeus 0 0 0 0 0 2 0 0 0 0 0 0
TABLE 2 (Continued)
Dwarf-Low Medium Low-Medium Tall Wh1te Spruce-White Spruce-White Black
Birch Birch Willow Alder Paper Paper Paper White Spruce Spruce
Alpine Shrub Shrub Shrub Shrub Cottonwood Birch Birch Birch Spruce Scattered Dwarf
Habitat var1ab le Tundra Thicket Thicket Thicket Thicket Forest Forest Forest I Forest II Forest Woodland Forest
Alaska spiraea, S[!iraea
beauverd1ana 0 0 0 0 0 0 0 5 0 0 0
Greene mountain ash,
Sorbus sco[!ul1na 0 0 0 0 0 0 16 0 24 0 0 0
Prickly rose, Rosa
acicularis 0 0 0 0 0 0 0 0 5 2 0 0
Dev1l's club, Echinopanax
horridum 0 0 0 0 0 20 0 0 0 0 0 0
High bush cranberry,
Viburnum~ 0 0 0 0 0 71 0 0 13 0 0 0
N
\.0 TOTAL LENGTH OF EDGE (m) 160 90 233 180 0 0 0 0 90 79 0
AVERAGE SLOPE (degre~~' 7.1 . 2.2 5.4 6.0 22.2 0 21.8 20.8 0 1.0 5.0 1.0
MEAN ASPECT (degrees) 311 150 215 356 143 0 159 144 0 276 195 168
ELEVATION (m) 1300 1100 900 880 1200 180 600 600 260 520 820 730
*Low Shrubs
TABLE 3
FREQUENCIES (~) OF SHRUB AND HERB SPECIES IN THE GROUND COVER OF INTENSIVE STUDY PLOTS, UPPER SUSITNA RIVER BASIN, ALASKA, JULY-AUGUST 1980-8I. BASED
ON OCCURRENCE IN 40 1.0 m x 1.0 m SAMPLE PLOTS LOCATED AT THE MMIMAL TRAPSITES ON LINES THREE AND FIVE OF THE 10-HA STUDY PLOTS, EXCEPT ON THE ALPINE
TUNDRA AND DWARF-LOW BIRCH SHRUB THICKET PLOTS. WHERE THE 1.0 m x 1.0 m PLOTS WERE LOCATED AT TilE SINGLE VEGETATION SAMPLING SITE IN EACH OF THE 49
SUBPLOTS OF THE 10-HA PLOT.
Dwarf-Low Medium Low-Medium Tall Wh1te Spruce-White Spruce-White Black
Birch Birch Willow Alder Paper Paper Paper White Spruce Spruce
Alpine Shrub Shrub Shrub Shrub Cottonwood Birch Birch Birch Spruce Scattered Dwarf
Plant specf es Tundra Thicket Thicket Thicket Thicket Forest Forest Forest I Forest II Forest Woodland Forest
SHRUB
Alnus cri spa 13 3
Andromeda pol1folfa 3
Arctostaphylos rubra 13 10 5
Betula glandulosa/hybrfds 88 100 97 17 63 85 95
Cassiope tetragona 63
Cornus suecica/canadensis 70 95 33 93 73 100 53 100 15
w Diapensia lapponica 43
0 Dryas octopetala 53
Echinopanax ho.rridum 33
Empetrum n igrum 94 100 67 3 7 40. 37 100 97
Led urn pa 1 us tre 6 29 97 20 16 6 85 97 93
Linnaea borealis 7 37 90 85 97 40 43
Loiseleuria procumbens 4 6
Oxycoccos microcarpus 3 3 45
Potentflla fruticosa 10 3 3
Ribes glandulosum 7 55
Ribes triste 57 27 10
Ribes spp. 25
Rosa acicularis 10 27 33 3 10 55 27 17
Rubus idaeus 5 30 5 40
Sa lfx arctica 73 45
Salix bebbiana 3
s. myrtillifolia 3
s. novae-angliae 3
S. planHolia 10 18 97 3 20
S. reticulata 28 2 40 3 3
Salix spp. 14 15 5 3 5 33
TABLE 3 (Continued)
Dwarf-Low Medium Low-Medium Tall White Spruce-White Spruce-White Black
Birch Birch Willow Alder Paper Paper Paper White Spruce Spruce
Alpine Shrub Shrub Shrub Shrub Cottonwood Birch Birch Birch Spruce Scattered D~1arf
Plant species Tundra Thicket Thicket Thicket Thicket Forest Forest Forest I Forest II Forest Woodland Forest.
I
Sorbus scopulina 2
Spiraea beauverdiana 8 85 27 33 55 27 65 60 17
Vaccinium ovalifolium 3
Vaccinium u11ginosum 55 96 40 63 27 17 55 50 97 100
Vaccinium vitis-idaea 33 94 100 57 35 43 13 92 100 97 100
Viburnum edule 10 3 55 7 ·w
FORB
Achillea spp. 40 3 5
Aconitum delph1nifolium 30 13 5
w Actaea rubra 17 ..... Anemone spp~ 45 82 35
Antennar1a sp. 6
Arnica latifolia 3
Artemisia arct1ca 2 24 20 20
Artemisia sp. 33
Boykinia richardsonii 12
Campanula lasiocarpa 2
Circaea alp1na 3
Delphinium glaucum 5
Dodecatheon frigidum 2
Epilobium angustifolium 23 93 47 13 50 47 7 17
Erigeron peregrinus 10
Ga 1 i um bo rea 1 e 23 3 3
Gal ium trifidum 90
Gentiana spp. 12 29 23
Geocaulon 11vidum 5 20
Geranium erianthum 3
Geum rossi 1 6
Hedysarum alpinum 10
Heracleum lanatum 10
TABLE 3 (Continued)
Dwarf-low Medium low-Medium Tall White Spruce-White Spruce-White Black
Birch Birch Willow Alder Paper Paper Paper White Spruce Spruce
Alpine Shrub Shrub Shrub Shrub Cottonwood Birch Birch Birch Spruce Scattered Dwarf
Plant species Tundra Thicket Thicket Thicket Thicket Forest Forest Forest I Forest II Forest Woodland Forest
Hferacium gracile 35
Ustera cordata 10 17
lloydia serotina 10
lupinus nootkatensis 7
Mertensia paniculata 55 35 20 10 15
Oxytropis nigrescens 10
Parrya nudicaulis 22 10
Pedtcularis spp. 36 12 3 33 5 5
Petasites hyperboreus 27 10 3 43
Platanthera dilitata 3
w Polemonium acutiflorum 57
N
23 3 7
Polygonum bistorta 24 6
Potentilla palustris 20 3
Pyrol a spp. 4 2 27 83 10 7 50 3 15 3
Ranuncul us sp. 3
Rubus arcticus 17 30 5 5 10
Rubus chamaemorus 47 83 5 17 7 35 75
Rubus pedatus 83 70 95
Rumex arcticus 10 7
Sanguisorba stipulata 3 73 10 45 10
Saussurea angustifolia 7
Saxi fraga spp. 10
Sedum rosea 7
Senecio spp. 8 13 3
Solidago multiradiata 2 5 10 3
Stellaria spp 10 7 10 5
Streptopus amplexifolius 3 60 5 7
Thalictrum sparsiflorum 3
Thalictrum alpinum 40
Trientalis europaea 3 10 17 27 90 80 65 3
Valeriana capitata 2 15
TABLE 3 (Continued)
Dwarf~Low Medium Low-~ledium Tall White Spruce-White Spruce~ White Black
Btrch Birch Will OW Alder Paper Paper Paper White Spruce Spruce
Alpine Shrub Shrub Shrub Shrub Cottonwood Birch Birch Birch Spruce Scattered Dwarf
Pl~nt species Tundra Thtcket Thicket Thicket Thicket Forest Forest Forest I Forest II Forest Woodland Forest
GRASS
Calamagrost1s canadensis 83 87 80 95 95 15 23 7
Deschampsia spp. 7 57
Festuca al taica 2 51
Hierochloe alpina 59 53
Grass. unidentified 6 77 93 57 10
SEDGE
Carex microchaeta 68 59
Carex spp. 6 65 5 5 5 5 15 85
w Eriophorum callatr1x 6 w Eriophorum sp. 3
Sedge. unidentified 6 100 12
HORSETAIL
Equi setum spp. 7 95 17 70 20 73 50 27 43 40
FERN
Dryopteris d1latata 47 17 40 2
Gymnocarpium dryopterts 55 33 60 67
~latteuccia struthiopteris 7
Thelypteris phegopter1s 7
CLUB MOSS
Lycopodium spp. 10 17 20 3 50 33 100 7 20 3
Selaginella sibirica 8
MOSS 98 98 100 100 77 83 97 95 97 100 100 100
.!J.Q!ft:! 90 100 100 15 63 3 35 35 7 97 100 83
Meadow \'/as domi~ated by Carex microchaeta and contained significant
quantities of dwarf shrub (up to 50% of ground cover), primarily
Cassiope tetragona, Dryas octopetala, Salix arctica, ~· reticulata,
Vaccinium uliginosum, and some~· planifolia. The drier Dwarf Shrub Mat
habitat was dominated by mosses (Pleurozium schreberi and Polytrichum
commune}, fruticose lichens, and Cassiope tetragona, with considerable
Carex microchaeta and Dryas octopetala and some Vaccinium uliginosum.
The block-field habitat was predominantly rock detritus, with varying
amounts of crustose and fruticose lichens (20-40% cover} and mosses (up
to 60% cover). The plot was on a northwest-facing terrace, sloping an
average of 7°, on a north shoulder of Mt. Watana at 62°44'37 11 N,
148°05'42 11 W, and at about 1300 m (4300 ft) elevation.
The vegetation reflected the harsh environmental conditions at this
plot. In 1981, an extensive snowbank still covered the southern edge of
the plot on 15 May and lasted most of the summer. Vegetation began to
turn green rapidly on 29 May, after. a rain, although a few plants were
in bloom earlier. High winds were frequent, and a cold snap during the
second week of June brought nightly temperatures to -4°C. Fresh snow
blanketed the plot with a 10 em layer on 9 June, and about 7 em fell
again 28-30 June and may have been responsible for nesting failures.
By late July, vegetation was already browning again; and, beginning on
14 August, regional precipitation fell mostly as autumnal snows at this
high elevation.
(b) Dwarf-Low Birch Shrub Thicket
·The plot consisted of a relatively unifonn stand of shrub birch (Betula
glandulosa/nana), with interspersed open patches where snow lingered in
spring. Average shrub height was 0.5 m. The ground cover was fairly
unifonn throughout, even in the ',~pen patches; it was dominated by micro-
shrubs (Empetrum nigrum, Vaccinium vitis-idaea, y. uliginosum), moss,
and fruticose lichens. Birch and moss generally contributed less and
34
grass (Hierochloe alpina and Festuca altaica) more to the ground cover
in the open patches than in the shrubby areas. The plot was located on
a 4° south-southeast-facing slope near the top of a dry, broad knoll
east of Kosina Creek, at 62°42 1 47" N, 147°53 1 50 11 W, and at 1100 m
(3600 ft) elevation.
(c) Medium Birch Shrub Thicket
A dense, homogeneous stand of 1.4 m-high shrub birch characterized this
plot. Ground cover consisted of thick moss and a dense mat of micro-
shrubs, especially Empetrum nigrum, Vaccinium vitis-idaea, Ledum
palustre, and lesser amounts of Spiraea beauverdiana. The plot was
along a broad, relatively dry ridge that sloped slightly to the
southwest. It was located west of Tsusena Creek, at 62°52 1 17" N,
148°37 1 05 11 W, and at 900 m (3000 ft) elevation.
(d) Low-Medium Willow Shrub Thicket
Although a rather heterogeneous plot, the vegetation was dominated by
willow, primarily Salix p1anifolia pulcflra and~-barclayi. Dense low
shrubs, predominantly willow, occurred throughout the plot, with inter-
spersed wet sedge meadow openings present on the upper third of the
plot. Medium-height shrubs of shrub birch and willow grew on the lower
two-thirds of the plot. Ground cover consisted of about equal percent-
ages of microshrubs (especially Cornus sp., Empetrum nigrum, Vaccinium
uliginosum, andy_. vitis-idaea, with lesser amounts of Salix
reticulata), sedges, many species of forbs (including relatively high
frequencies of Equisetum arvense, Rubus chamaemorus, Sanguisorba
stipulata, Polemonium acutifolium, and t4ertensia paniculata), and
litter. The substrate was moist to wet, and the above-mentioned ground
cover vegetation was underlain by moss. The plot was on the north-
facing 6° slope of a draw west of Tsusena Creek, at 62°51 1 10 11 N,
148°45 1 50" W, and at 880 m (2900 ft) elevation.
35
(e) Tall Alder Shrub Thicket
The plot was dominated by dense, tall Sitka alder (Alnus crispa
sinuata), averaging 88 yr old (oldest 158 yr) and 3.6 m in height. The
upper half to two-thirds of the plot was dense alder, whereas the lower
portion had some openings and intrusions of small groups of white spruce
trees (x=60 yr; oldest 134 yr). Ground cover was predominantly leaf and
grass litter, with moderate amounts of dwarf and microshrubs (Linnaea
borealis, Vaccinium vitis-idaea, Spiraea beauverdiana, Cornus sp.,
y. uliginosum, Rosa acicularis, and Ribes spp.), grass, and forbs. The
plot was on a steep, southeast-facing slope east of Watana Creek, at
62°50'40" N, 147°59'00" W, at approximately 1200 m (4000 ft) elevation.
(f) Cottonwood Forest
A dense stand of tall, mature cottonwoods or balsam poplar (Populus
balsamifera), averaging 133 yr old (oldest 176 yr), 17.6 m tall, and
34 em dbh, dominated this plot. The forest was homogeneous, except for
an old, overgrown river channel that intruded into the northern edge,
resulting in a narrow strip of only dense alder and no trees. There was
a two-level understory--an alder (Alnus spp.) layer with a canopy top at
about 6 m, and a medium shrub layer of high bush cranberry (Viburnum
edule) and devil's club (Echinopanax horridum). A 28% low shrub cover
consisted primarily of Ribes triste, Rosa acicularis, and Rubus idaeus;
and the ground cover was composed of more than 97% litter and many
forbs, most commonly Galium trifidum, Pyrola spp.,_ Streptopus
amplexifolius, and Epilobium angustifolium. Eguisetum spp. and the
ferns Dryopteris dilatata, Gymnocarpium dryopteris, and Matteuccia
struthiopteris were frequent, and there were many fallen logs. The plot
was located on the Susitna River floodplain near Sherman, at
62°42'10" N, 149°49'45" W, and at 180m {600 ft) elevation.
36
(g) Paper Birch Forest
The plot was composed predominantly of mature paper birch (Betula
papyrifera) that averaged 66 yr old (oldest 90 yr), 13.5 m tall, and
21 em dbh; although patches of white spruce (x=101 yr, oldest 194 yr)
intruded into the s~uthwest corner. There were patches of heavy under-
growth of tall alder, and this was·'one of only two plots in which Greene
mountain ash (Serbus scopulina) occurred. The forest floor had a high
·cover (88%) of litter, and a moderate cover (30 and 38%, respectively)
of forbs and of dwarf and microshrubs, including Cornus sp., Linnaea
borealis, Spiraea beauverdiana, and Vaccinium vitis-idaea. The plot was
on a steep south-southeast-facing, rocky, terraced slope, with rock
cliffs 3m to 6 m high. It was located on the north wall of the Susitna
River canyon 8 km downstream from Devil Creek, at 62°48'46 11 N,
149°11'30 11 W, and at 600 m (2000 ft) elevation.
(h) White Spruce-Paper Birch Forest I
An open, uniform stand of mature white spruce (Picea glauca) and paper
birch (Betula papyrifera) dominated this mixed deciduous-coniferous
forest. The spruce trees were older and larger than the birch, the
former averaging 139 yr old (oldest 185 yr), 14.3 m tall, and 24 em dbh
and the latter averaging 103 yr old (oldest 145 yr), 11.3 m tall, and
20 em dbh. Similar to the deciduous forest plots, this one had a dense
undergrowth of tall alder. There was a moderate cover (33%) of low
shrubs (especially Ribes spp., Rubus idaea, and Spiraea beauverdiana)
and microshrubs (Cornus sp., Linnaea borealis, and Vaccinium vitis-
idaea). Ground cover was dominated by litter, with lesser amounts of
forbs, especially, as in the·paper birch forest, Trientalis europaea and
Rubus pedatus. The ground cover had the highest percentage of grass of
any 10-ha plot, 28.7%. The plot was located a little northeast of the
Paper Birch Forest plot and was on a steep slope of a tributary drainage
on the north side of the Susitna River (62°49'10 11 N, 149°08'25 11 W, 600 m
[2000 ft] elevation).
37
(i) White Spruce-Paper Birch Forest II
Paper birch and white spruce dominated this mature mixed forest also,
but in this stand the birch, even though younger, were larger than the
spruce. The birches averaged 73 yr old (oldest 98 yr), 14.0 m tall, and
22 em dbh, and the spruce averaged 126 yr old (oldest 140 yr), 12.2 m.
tall, and 16 em dbh. Tree density and canopy coverage were twice those
in Mixed Forest I and, concomitantly, the heavy understory of alder
found in Mixed Forest I was absent in t4ixed II. In fact, except for the
dwarf shrub layer (<0.4 m}, which exceeded that of Mixed I, other shrub
layers lacked the coverage and density of Mixed I. The dominant ground
cover species, both woody and herbaceous, were similar in the two mixed
plots, although Mixed II had a higher moss cover and higher frequencies
of Cornus sp., Vaccinium spp., Pyrola secunda, Rubus pedatus, and
lycopodium annotinum. The plot was located on a flat terrace on the
south bank of the Susitna River, at 63°49'05" N, 149°32'26" W, and at
260 m (850 ft) elevation.
(j) White Spruce Forest
Mature white spruce trees (Picea glauca) dominated this plot, but a few
black spruce (Picea mariana) were scattered through6ut and increased in
frequency toward the southwest corner. The white ~pruce averaged 127 yr
old (oldest 145 yr), 10.1 m tall, and 19 em dbh, ~Y"hereas the black
spruce averaged 83 yr old (oldest 122 yr), 8.1 m tall, and 12 em dbh.
There were many dead spruce snags of both species standing on the plot,
with an average distance between snags of 11.3 m. Thirteen snags with
complete tops and identifiable as white spruce averaged 13.3 m tall, and six
identifiable as black spruce averaged 10.8 m tall. Many small spruce
indirated continued regeneration by both species. The deciduous shrub
und~rstory consisted primarily of shrub birch, paper birch, and alder.
Ground cover was predominantly moss, with considerable interlacing of
lichens and of dwarf and microshrubs, especially Vaccinium vitis-idaea,
38
Ledum palustre, Cornus sp., andy. uliginosum.
absent. The plot was located on an old outwash
Kosina Creek, at 62°47'00" N, 147°57'16" W, and
elevation.
(k) White Spruce Scattered Woodland
Litter was essentially
plain at the mouth of
at 520 m (1700 ft)
The dominant trees on the plot were mature, but relatively short, white
spruce (Picea glauca), averaging 146 yr old (oldest 310.yr), 9.0 m tall·,
and 22 em dbh. They were widely scattered throughout the plot, becoming
somewhat denser toward the southeast corner; average distance between
trees was 20.6 m. Amid the spruce was a relatively dense medium and
low shrub cover of shrub birch, averaging about 1.5 m high. Beneath
this layer was a dense cover (80%) of dwarf and microshrubs, especially
Cornus sp., Empetrum nigrum, Ledum palustre, Vaccinium uliginosum, and
y. vitis-idaea, and a relatively high ground cover of moss. The plot
was located on a south-southwest-facing slope just north of the mouth of
Tsusena Creek, at 62°51'47" N, 148°35'50" W, and at 820 m (2700 ft)
elevation.
(1) Black Spruce Dwarf Forest
An open stand of stunted black spruce (Picea mariana) composed this
plot. The spruce averaged 80 yr old (oldest 98 yr), 'but averaged only
2.9 m high and 4 em dbh {and hence are treated as "shrubs" in Table 2).
They were somewhat· clump_ed in distribution and became more dense toward
the west edge' of the plot. There was a moderate cover (35%) of low
shrubs, composed mostly of shrub birch and black spruce, and a denser
cover (64%) of dwarf shrubs, primarily Vaccinium uliginosum, y. vitis-
idaea, Empetrum nigrum, 1adum palustre, and shrub birch. The predomi-
nant ground cover was moss ( 79%). There was an extensive area of water
seepage through this slightly sloping plot and some hummocky ground.
The plot was located in the Fog Lakes area, at 62°47'48" N,
148°28'15" W, at 730 m (2400 ft) elevation.
39
3.2 -Species Composition and Relative Abundance
To date, 135 species of birds have been recorded in the upper Susitna
River Basin study area. A complete annotated list of these species is
included in Section 3.7. The relative abundance of these species (see
Tables 4-7) is largely a function of habitat availability, with Common
Redpoll, Savannah Sparrow, White-crowned Sparrow, Lapland Longs pur-; and
Tree Sparrow being the most abundant species. Redpolls are habitat
generalists, while the other abundant species are birds of the shrublands
(dwarf, low, and medium shrubs), vegetation types that cover 70% of the
region (Plant Ecology report, APA 1982).
Fifteen species are ranked as rare in the region on the basis of current infor•
mation: four raptors (Osprey, American Kestrel, Snowy Owl, Boreal Owl), three
species of prairie ducks (Gadwall, Blue-winged Teal, Ring-necked Duck), four
. shorebirds (Upland Sandpiper, turnstone sp., Surfbird, Sanderling), three small
land birds (Black-backed Three-toed Woodpecker, Western Wood Pewee, Yellow
Warbler), and Ruffed Grouse. Most of these birds are at the periphery of their
geographic ranges, although lack of appropriate habitat may limit a few. All
are represented, however, by larger populations in other portions of Alaska.
An Easte.rn Kingbird on 11 July 1980 is considered acci"dental in the
region. In Alaska this species is a regular visitant only in South-
eastern; it is casual elsewhere in the state (Kessel and Gibson 1978).
3.3 -Breeding Bird Densities
Avian population levels varied greatly among the different habitats
(Table 8), as, of course, did the level of use of each habitat by dif-
ferent species (Table 9). The presence or abs~~ce of a given species in
a habitat is largely a function of species' hubitat preferences, but
habitat occupancy levels are affected by a number of factors, including,
in interior A.laska, habitat structural complexity and primary produc-
tivity (Spindler and Kessel 1980).
40
TABLE 4
RELATIVE ABUNDANCE OF LOONS. GREBES. AND WATERFOWL, UPPER SUSITNA RIVER BASIN, ALASKA. BASED PRIMARILY ON TOTAL NUMBER OBSERVED ON 1980 AND 1981
AERIAL SURVEYS AND 1981 GROUND SURVEYS.
Spring Migration
(Aerial & Ground,
1981)
No. Species
802 Scaup spp.
394 Mallard
366 Pintail
262 American Wigeon
215 Green-winged Teal
210 Sco ter spp.
140 Goldeneye spp.
102 Oldsquaw
52 Merganser spp.
51 Snow Goose (~1 flock)
46 Canada ·Goose
43 Northern Shoveler
43 Swan spp.
31 Redhead
23 Bufflehead
11 Common Loon
8 Arctic Loon
6 White-fronted Goose
5 Red-necked Grebe
4 Canvasback
3 Red-throated Loon
3 Horned Grebe
3 Blue-winged Teal
3 Gad~1all
2 Ring-necked Duck
*40 fr~n aerial survey
FAIRLY COMMON
UNCOMMON
Fall Migration
(Aerial: 7 Sept-3 Oct 80
15 Sept-23 Oct 81)
No. Species
2658 Scaup spp.
905 Mallard
874 American Wigeon
718 Goldeneye spp.
551 Seater spp.
514 Bufflehead
299 Merganser spp.
277 Swan spp.
233 Pintail
142 Green-winged Teal
111 Oldsquaw
71 Canada Goose
35 Horned Grebe (1980)
33 Red-necked Grebe
28 Northern Shoveler
17 Common Loon
}cOMMON
FAIRLY COMMON
UNCOM~!ON
14 Ring-necked Duck (1980) }
1 Blue-winged Teal (1980) RARE
Summer
(Ground, 1981)
No. Species
94 Scaup (incl. 41 L, 27 G)
Bl White-winged Seater
(incl. flock of 65)
60 Pintail
59 Trumpeter Swan*
55 Oldsquaw
47 Mallard
33 Surf Seater
32 American Wigeon
28 Green-winged Teal
26 Black Seater
25 Common Loon
24 Harlequin Duck
16 Northern Shoveler
11 Red-breasted Merganser
8 Red-throated Loon
8 Barrow's Goldeneye
7 Red-necked Grebe
7 Common Goldeneye
5 Horned Grebe
5 Common f.lerganser
4 Arctic Loon
FAIRLY COMMON
UNCOMMON
TABLE 5
RELATIVE ABUNDANCE OF LARGE LANDBIRDS AND CRANES, UPPER SUSITNA RIVER
BASIN, ALASKA. BASED PRIMARILY ON TOTAL NUMBER OBSERVED 17 APRIL-
23 OCTOBER 1981, EXCLUDING OBSERVATIONS FROM AIRCRAFT.
No. Species
182 Rock Ptarmigan
}COMMON 139 Common Raven
137 Willow Ptarmigan
71 Golden Eagle
}FAIRLY COMMON 52 Spruce Grouse
40 Marsh Hawk
'
27 Bald Eagle
21 White-tailed Ptarmigan
16 Goshawk
15 Sandhill Crane
07 Great Horned Owl
07 Gyrfalcon UNCOM~ION
07 Short-eared Owl
06 Red-ta i 1 ed Hawk
03 Merlin
02 Sharp-shinned Hawk
02 Hawk Owl
02 Snowy Owl
01 Osprey
01 American Kestrel ( 1980) RARE
01 Ruffed Grouse
01 Boreal Owl
42
TABLE 6
RELATIVE ABUNDANCE OF SHOREBIRDS AND GULLS, UPPER SUSITNA RIVER BASIN,
ALASKA. BASED PRIMARILY ON TOTAL NUMBER OBSERVED 17 APRIL-23 OCTOBER 1981,
BUT SUPPLEMENTED BY DATA FROM LATE SUMMER AND FALL 1980 FOR RARE SPECIES.
No. Species
163 Mew Gull
146 American Golden Plover
114 Common Snipe COMMON
103 Spotted Sandpiper
78 Northern Phalarope
69 Arctic Tern
58 Lesser Yellowlegs FAIRLY COMMON
55 Long-ta i 1 ed Jaeger
51 Least Sand pi per
44 Bonaparte's Gull
34 Baird's Sandpiper
22 Semipalmated Plover
20 Herring Gu11
19 Greater Yellowlegs
17 Whimbrel UNCOMMON
12 Semipalmated Sandpiper
09 Wandering Tattler
09 Pectoral Sandpiper
06 Solitary Sandpiper
03 Long-billed Dowitcher
06 Upland Sandpiper (1980)
02 Turnstone sp.
01 Su rfbi rd (1980 RARE
01 Sanderling (1980)
43
t
TABLE 7
RELATIVE ABUNDANCE OF SMALL LANDBIRDS. UPPER SUSITNA RIVER BASIN, ALASKA. BASED PRIMARILY ON TOTAL NUMBER OBSERVED 17 APRIL-23 OCTOBER 1981,
SUPPLEMENTED BY DATA FROM LATE SUMMER AND FALL 1980 FOR THE LESS NUMEROUS SPECIES.
. No. Specie·s
1161 Common Redpoll
669 Savannah Sparrow
631 \~hite-crowned Sparrow
588 Lapland longspu,
583 Tree Sparrow
420 Horned lark
398 Dark-eyed Junco
343 Ruby-crowned Kinglet
316 Yellow-rumped Warbler
288 Water Pipit
258 Varied Thrush
257 Gray Jay
249 Wilson's Warbler
225 Bohemian Waxwing
211 American Robin
195 Hermit Thrush
179 \Jhite-winged Crossbill
163 Fox Sparrow
146 Swainson's Thrush
145 Blackpoll Warbler
129 Boreal Chickadee
98 Snow Bunting
71 Arctic Warbler
64 Tree Swallow
62 Violet-green Swallow
55 Northern Waterthrush
54 Gray-cheeked Thrush
ABUNDANT
'
COM NON
FAIRLY COMMON
No. Species
53 Bank Swallow
46 Cliff Swallow
45 Gray-crowned Rosy Finch
42 Black-capped Chickadee
41 Golden-crowned Sparrow
35 Lincoln's Sparrow
33 Rusty Blackbird
29 Dipper
26 Pine Siskin
23 Northern Three-toed Woodpecker
23 Wheatear
22 Black-billed Magpie
,16 Belted Kingfisher
16 Olive-sided Flycatcher
14 Alder Flycatcher
13 Common Flicker
11 Brown Creeper
10 Hairy Woodpecker
10 Orange-crowned Warbler
09 Pine Grosbeak
05 Say's Phoebe
02 Townsend's Solitaire (+4 in 1980)
03 Northern Shrike {+27 in 1980)
02 Smith's Longspur (+5 in 1980)
01 Downy Woodpecker (+8 In 1980)
01 Golden-crowned Kinglet (+11 in 1980)
UNCOMMON
No. Species
1 Black-backed Three-toed
Woodpecker (1980)
4 Western Wood Pewee (1980}
2 Yellow Warbler (t3 in 1980}
1 Eastern Kingbird (1980} }-ACCIDENTAL
TABLE 8
AVIAN HABITAT OCCUPANCY LEVELS, UPPER SUSITNA RIVER BASIN,
BREEDING SEASON, 1981
Density
No. species (No. Biomass Species
(No. breeding territories/ (Grams/ diversity
Avian Census Plot SQecies) 10 ha} 10 ha) {HI}
Cottonwood Forest 21(16) 60.9 3653 2.55
White Spruce-Paper
Birch Forest II 22(13) 34.6 1836 2.07
White Spruce-Paper
Birch· Forest I 18(14) 41.8 1709 . 2.47
Paper Birch Forest 18( 10) 38.1 1814 2.05
White Spruce
Scattered Woodland 23(16) 43.8 1775 2.29
Black Spruce
Dwarf Fares t 23(13) 24.8 1166 2.43
Lov1-Med i urn
Willow Shrub 14(6) 45.4 1413 1.56
White Spruce Forest 18(8) 15.7 1059 1.83
Medium Birch Shrub 10(5) 32.5 952 1.48
Tall Alder Shrub 15(10) 12.5 888 2.05
Dwarf-Low Birch
Shrub 11(6) 10.6 355 1.29
Alpine Tundra 8(7} 3.9 211 1.73
45
TABLE 9
HUMBER OF TERRITORIES Of EACH BIRD SPECIES ON EACH 10-HECTARE CENSUS PLOT, UPPER SUSITNA RIVER BASIN, ALASKA, 1981. (+ ~ SMALL PORTION OF A BREEDIHG
TERRITORY ON CENSUS PLOT, COUNTED AS 0.1 JN DENSITY AND DIVERSITY CALCULATIONS; V =VISITOR TO PLOT.)
Dwarf-Low Medium Low-Medium Tall Wh lte Spruce-Whfte Spruce-White Black
Birch Btrch Wlllow Alder Paper Paper Paper White Spruce Spruce
Alpfne Shrub Shrub Shrub Shrub Cottonwood Birch Birch Birch Spruce Scattered Dv1arf
Species Tundra Thicket Thicket Thicket Thicket Forest Forest Forest I Forest II Forest Woodland Forest
Plntatl v
Goshawk v v
11arsh Hawk v
Spruce Grouse v v v 1.0 1.0 v v
Ruffed Grouse +
Willow Ptarmigan 0.5 v v
Rock Ptannfgan 0.7
White-tailed Ptarmigan +
hnerlcan Golden Plover v
Greater Yellowlegs +
Colllllon Snipe v v 0.5 1.0 Baird's Sandpiper 0.8 v
Long-tailed Jaeger v
Short-eared Owl v v
Colllllon Flicker v Hairy Woodpecker 1.0 1.0
Downy Woodpecker 0.5
N. Three-toed Woodpecker v 0.3 1.0 v v
""" Alder Flycatcher 1.0
0'1 Olive-sided Flycatcher v v
Horned Lark 0.3 v
Tree Swallow v v v Gray Jay 1.0 v 0.5 0.5 1.0 + v Black-billed Magpie v
Common Raven v Black-capped Chickadee 1.8 v v v Boreal Chickadee v 1.7 1.0 v v 1.0 Brown Creeper 2.0 1.0 American Robin 0.5 v v 0.5 0.5 Varied Thrush 1.5 10.0 3.5 2.5 3.3 2.9 v v Hermit Thrush 2.2 v 6.1 3.8 v Swalnson's Thrush 6.9 5.5 5.4 8.0 3.0 v v Gray-cheeked Thrush 3.8 v v 3.9 2.5 Arctic Warbler 4.8 3.6 2.8 Ruby-crowned Kinglet v v Water Pipit 0.5 3.3 1.0 4.2 0.8 4.0
Bohemian Waxwing v Orange-crowned Warbler v Yellow-rumped Warbler + 7.0 9.8 7.5 9.5 1.0 0.8 2.5 Blackpoll Warbler v 4.4 3.9 1.8 0.5 2.0 1.5 .Northern Waterthrush 6.1 + 2.5 v Wilson's Warbler 8.8 9.2 1.2 4.0 3.8 4.0 9.4 Rusty Bhckbl rd v Conmon Red po 11 v v 1.5 v 2.5 2.0 2.0 3.0 v 0.5 1.0 Pine Siskin v v White-winged Crossbill v v v v v v v Savannah Sparrow 1.0 5.8 3.0 12.3 v 2.5 O.B Dark-eyed Junco 2.8 1.8 2.5 3.9 4.5 2.5 2.0 2.0 Tree Sparrow 2.5 11.8 15.0 1.5 7.9 2.6 White-crowned Sparrow 0,3 4.1 3.8 + 3.5 6.5 2.5 Fox Sparrow v 1.6 4.6 1.0 1.9 v 3.5 2.9 lincoln's Sparrow v ,and Longspur 1.0 0.8
'1unting 0.2
Generally, in the upper Susitna River Basin, the forest and woodland
habitats supported higher densities and/or biomasses of birds than the
shrub communities. Highest densities in forests were found at the
downstream (Shennan) Cottonwood Forest plot, which supported 60.9 bird
territories/10 ha, and lowest densities were found in the White Spruce
Forest plot at the mouth of Kosina Creek (15.7 territories/10 ha). Of
the shrub habitats, Low-Medium Hillow Shrub had the highest densities
(45.4 territories/10 ha) and Dwarf Shrub-Alpine Tundra the 1owest ( 11
territories/10 ha). Bird density was also low in Tall Alder Shrub (12.5
territories/10 ha). Alpine tundra areas of upland cliffs and block-fields
and of mat and cushion tundra had the lowest bird usage, but supported
some bird species generally not found in other habitats, e.g., White-tailed
Ptannigan, Horned Lark, Wheatear, Water Pipit, Gray-crowned Rosy Finch,
and Snow Bunting.
Preliminary comparisons between occupancy levels in habitats of the ·
upper Susitna River Basin and those in similar habitats in the upper
Tanana River Valley (Spindler and Kessel 1980) show many parallels. In
both regions Paper Birch Forest and the Mixed Deciduous-Coniferous
Forest supported intermediate levels of bird populations and Coniferous
Forest the lowest. The Scattered Woodland and Dwarf Forest habitats,
with their openness and added shrub components, also supported inter-
mediate occupancy levels, however, even with major coniferous components.
The lower-height shrub thickets had low numbers of species, apparently_
because of relatively simple habitat structure, and there were di f-
ferences in occupancy levels between plots with a dry substrate and ones
with high substrate moisture. .Habitat diversity and a wet substrate
probably allowed higher occupancy levels on the Susitna Low-Medium
Willow Shrub plot compared to other shrub plots.
ThPu most conspicuous difference between the upper Susitna and Tanana
valleys was in the Tall-Shrub Thickets. Tall shrubs in interior Alaska
supported the highest avian occupancy levels of any habitat (Spindler
47
and Kessel 1980), but, unlike in the Susitna study area, these thickets
were dominated by willow, thinleaf alder {Alnus tenuifolia), and balsam
poplar {Populus balsamifera), which have average to above average levels
of primary productivity. The tall shrub thickets of the Susitna study
area were composed almost entirely of Alnus crispa, which has relatively
lm'l levels of primary productivity (Spindler and Kessel 1980) and which,
in interior Alaska and on the Seward Peninsula, also supports relatively
few birds (Kessel, pers. obs.).
3.4 -Waterbird Use of W~tla.nds
(a) Summer Populations
The wetlands of the region supported relatively few waterbirds during
the summer, both in respect to number of species and number of indivi-
duals. The relative abundance of loons, grebes, and waterfowl as deter-
mined from all observations is shown in Table 4. The number and density
of adults and broods of waterbirds observed during the intensive ground
surveys of 28 ponds and. lakes during July 1981 are shown in Table 10.
The density of adult birds derived from the intensive ground survey of
20.5 km 2 of wetlands was 23.8 adults/km 2• By comparison, a similar
census of 13 of the more productive waterbodies of the upper Tanana
River Valley, east-central Alaska, in 1977 and 1979 showed, respec-
tively, 183.3 and 110.9 adults/km2 of wetlands (Spindler et al. 1981)*.
The number of broods was co·rrespondingly low, with 2.9 broods/km 2 of
wetlands in the upper Susitna River Basin in 1981,
*Regional comparisons of densities obtained by the waterbody census
method can only be made if the distribution of waterbody size classes is
similar between regions (Spindler et al. 1981), which was the case for
the sets of sampled waterbodies used here.
48
TABLE 10
NUMBER OF ADULT WATERBIRDS (OR 2INDEPENDENT YOUNG) AND BROODS FOUND ON 28
WATERBODIES (TOTAL = 20.5 Kf~ OF WETLANDS)1 UPPER SUSITNA RIVER BASIN 1
ALASKA, JULY 1981. ARRANGED IN DECREASING ORDER OF ADULT NUMBERS.
Species No. adults No. broods
White-winged Seater 81 (incl. flock 65) 0
Arctic Tern 48 0
Oldsquaw 47 11
Mew Gull 43 7
Lesser Scaup 36 4
scaup sp. 9 1
Surf Seater 33 2
Black Seater 26 11
seater sp. 6 1
Greater Scaup 25 0
Northern Phalarope 23 0
Common Loon 22 3
Trumpeter Swan . 16 1
Mallard 10 1
Red-throated Loon 8 0
American Wigeon 8 6
Red-necked Grebe 7 1
Pintail 7 2
Northern Shoveler 7 1
Goldeneye·sp. 6 1 (= Common)
Horned Grebe 5 5
Bonaparte's Gull 5 0
Bald Eagle 3 0
Arctic Loon 2 0
Green-winged Teal 2 1
Red-brea;;ted Merganser 1 1
Merganser sp. 1 0
TOTAL 487 60
No./km 2 23.8 2.9
49
compared to an average of 6.2 broods/km 2 in the upper Tanana River
Valley (ibid.). Productivity in the eastern portion of the upper Tanana
River Valley study area in 1979 was 30-40% lower than historically at
Minto Lakes and the Yukon Flats (Kessel et al. 1980). Minto Lakes,
Tetlin Lakes, and portions of the Yukon Flats are considered among the
most productive wetlands in Alaska (J. G. King, U. S. Fish and Wildlife
Service, pers. comm.). Thus, the waterbodies of the upper Susitna River
Basin appear to support a relatively impoverished population of water-
fowl during the summer.
The species composition of waterfowl in the region showed some differ-
ences from that of central Alaska as a whole, in part reflecting the
subalpine nature of much of the study area. Oldsquaw and Black Seater
were the most productive of the waterfowl in 1981 (Table 10). Both
species are primarily tundra nesters, and the Alaska Range is the only
inland nesting location known for the Black Seater in Alaska (Gabrielson
and Lincoln 1959). On the other hand, the Pintail, which is one of the
most numerous ducks in central Alaska, occurred in relatively small
numbers in the study area, in spite of the fact that both 1980 and 1981
were high population years for Pintails in Alaska, due to severe drought
in the Canadian prairie provinces (King and Conant 1980, Conant and King
1981).
Trumpeter Swans bred canmonly at the eastern end of the study area, from
. the vicinity of the Oshetna River at' least to the Maclaren River. On a
random flight over the ponds of this area on 4 August 1981, we had
19 observations of Trumpeter Swans. We counted 40 adult birds, includ-
ing 9 pairs with broods, totaling 28 cygnets. This area is the western
edge of the Gulkana Basin Trumpeter Swan population, which has more than
doubled during the past five y~ars (King and Conant 1981).
50
(b) Populations During Migration
Summaries of the numbers and species composition of loons, grebes, and
waterfowl enumerated during aerial surveys in fa11 1980 and 1981 and
spring 1981 are given in Tables 11-13, and relative abundance rankings
for species in fall and spring are given in Table 4. Based on these
data, the upper Susitna River Basin, which is on a high plateau between
the Alaska Range and the Talkeetna Mountains, does not appear to be a
major migration route ior waterbirds (contra U. S. Corps of Engineers
1977).
Scaup, including both Lesser and Greater scaup, were the most numerous
species group during both spring and fall. Relatively large numbers of
Mallards and American Wigeon also moved through during both seasons
(although we missed peak wigeon numbers in fall 1981 surveys). Pintails
were common during spring migration but uncommon in fall. Few geese or
cranes were seen at either season.
The upper Susitna River Basin was less important to migratory waterfowl
in spring than fal.l. The difference was probably due largely to the
·L.ime of ice breakup, which occurred after the main spring migratory
movement of many species, especially the dabbling ducks and Common
Goldeneye. Early migrants used the Susitna River itself and the tha\'led
edges of lakes. Use of the region's waterbodies increased toward the
end of May, concurrent with the availability of more open water and the
influx of the later-arriving loons, grebes, scaup, Oldsquaw, seaters,
and mergansers. The relatively high Importance Values (see below) of
the large lakes of the region in spring reflect their use after thaw by
these later-arriving species.
The pattern of fall movement in the region was similar to that known for
the rest of central Alaska. That is, peak numbers of American Wigeon,
Pintail, and Green-winged Teal occurred during the first half of
51
TABLE 11
SUMMARY OF TOTAL NUMBERS AND SPECIES COMPOSITION OF WATERBIRDS SEEN ON SURVEYED WATERBODIES DURING AERIAL SURVEYS OF THE UPPER
SUSITNA RIVER BASIN, FALL 1980
DATE OF SURVEY
Species 7 Sept 11 Sept 16 Sept 20 Sept 26 Sept 3 Oct TOTAL
Loon spp. 4 5
Common loon 3 2 3 8
Red-necked Grebe 2 3 4" 5 3 17
Horned Grebe 1 4 17 9 2 2 35
Swan spp. 34 29 9 12 20 104
Canada Goose 1 20 21
American Wigeon 155 325 97 88 56 721
Green-winged Teal 30 83 9 1 2 125
en Mallard 10 64 14 116 110 124 438 N Pintail 60 60 53 21 3 4 201
Blue-winged Teal 1 1
Northern Shoveler 8 20 28
Ring-necked Duck 2 12 14
Scaup spp. 165 347 499 370 293 180 1854
Oldsquaw ' 7 4 13 13 16 4 57
Black Scoter 8 38 25 24 10 105
Scoter spp.* 6 56 72 134
Surf Seater 5 4 2 11
Uh1te-winged Scoter 10 1 6 1 18
Bufflehead 33 40 95 127 101 396
Goldeneye spp. 15 36 68 124 95 133 471
Merganser spp. 8 30 36 68 19 161
TOTAL BIRDS 270 803 1241 953 927 731 4925
Total wetland area surveyed (km 2) 13.11 22.08 25.76 27.53 29.00 24.25
Density (birds/km 2 of wetlands) 20.6 36.4 48.2 34.6 32.0 30.1
* Surf or Uhite-winged seater
TABLE 12
SUMMARY OF TOTAL NUMBERS AND SPECIES COMPOSITION OF WATERBIRDS SEEN ON SURVEYED WATERBODIES DURING AERIAL SURVEYS OF THE UPPER
SUSlTNA RIVER BASIN. FALL 1981
DATE OF SURVEY
Species 15-16 Sept 26 Sept 26 Sept-9 Oct 12-19 Oct 20-23 Oct TOTAL
Common Loon 2 3 3 1 9
Arctic Loon
Red-throated Loon
Loon spp.
Red-necked Grebe 12 3 16
Horned Grebe
Whistling Swan 18 24 42
Trumpeter Swan 6 10 l4 30
Swan spp. 41 25 22 13 101
Canada Goose 50 50
Mallard 41 153 131 142 467
Pinta 11 32 32
Green-winged Teal 13 3 16
(J'I Northern Shoveler
w Amer1can Wigeon 133 14 5 152
Canvasback
Redhead
Scaup. Greater and Lesser 479 166 51 90 786
Goldeneye, Common and Barrow's 18 125 68 36 247
Bufflehead 17 20 29 52 118
Oldsquaw 15 31 7 1 54
Wh i te-1~1 nged Seater 69 13 82
Surf Scoter 29 29
Black Scoter 1 6 2 1 10
Scoter spp. 69 1 92 162
Common Merganser 1 2 3
Red-breasted Merganser·
Merganser spp. 77 38 18 133
TOTAL BIRDS 915 607 436 568 13 2539
Total wetland area surveyed (km 2) 25.68 25.68 21.31 11.57 6.62
Km 2 of 100% frozen waterbodies
surveyed* 0 1.41 3.91 3.76** 2.00
Density (birds/km2 of wetlands) 35.6 23.6 20.5 49.1 1.96
* Other waterbodies had at least some open water.
** An additional 9.22 km 2 of 100% frozen waterbodies were not surveyed in mid-October because they were known to be frozen.
By late October only Stephan and Murder lakes still had some open water.
(11
~
TABLE 13
SUMMARY UF TOTAL NUMBERS AND SPECIES COMPOSITION OF WATERBIRDS SEEN ON SURVEYED WATERBODIES DURING AERIAL SURVEYS OF THE UPPER
SUSlTilA RIVER BASIN, SPRING 1981
DATE OF SURVEY
Species · 3 May 10 l·lay 26 May TOTAL
Common loon 4 4
Arctic Loon 5 5
Red-throated Loon 2 2
Loon spp. 3 4 7
Red-necked Grebe 4 4
llorned Grebe 1 2
Wh1stling Swan
Trumpeter Swan 2 6 8
Swan spp. 11 10 21
Canada Goose
Mallard 97 78 121 296
Pintail 71 70 116 257
Green-1~inged Teal 67 47 38 152
Northern Shoveler 12 28 40
Americw Wigeon 5 94 99 198
Canvasl..ack 1 1
Redhead 28 28
Scaup, Greater and lesser 103 513 616
Goldeneye, Common and Barrow's 51 38 89
Bufflehead 2 10 12
Oldsquaw 2 84 86
Whitc-w1nged Scoter 16 16
Surf Scoter 4 35 39
Black Scoter 1 42 43
Scoter spp. 12 74 86
Common Merganser 7 7
Red-breasted Merganser 2 2
Merganser spp. 25 25
TOTAL BIRDS 242 492 1312 2046
Total wetland area surveyed (km 2) 25.68 25.68 25.68
Km 2 of 100% frolen waterbodfes
surveyed* 14.31 1.97 0
Density (birds/km 2 of wetlands) 9.4 19.2 51.1
* Other waterbodies had at least some open water.
September; of loons, grebes, and scaup during the second and third weeks
of September; of Oldsquaw and mergansers during the last half of
September; and of Mallards, seaters, Buffleheads, and goldeneyes from
the last third of September to mid-October. Swan migration, which
included both Trumpeter and Whistling swans, occurred between the last
week of September and the end of October.
(c) Relative Importance of Waterbodies
Use by birds of the various waterbodies* of the region differed con-
siderably. Waterbodies included among the six highest Importance Value
(I.V.) ratings (see Section 2.8) for at least one season are listed with
seasonal population statistics in Table 14.
Of these more important waterbodies, WB 106 and 107, Stephan and Murder
lakes, respectively, were among the top three in Importance Values for
all seasons. Stephan Lake received twice the use in fall'as in spring,
but both waterbodies consistently had relatively high levels of species
richness, while large Stephan Lake had high numbers of birds and smaller
Murder Lake, high densities. These lakes assumed additional importance
in early spring and late fall because of ice conditions. Murder Lake,
which reportedly has some open water all winter, provided some of the
first open water for early spring migrants, as did the inlet of Stephan
Lake; Green-winged Teal, Mallard, and Pintail were using this open water
on 3 May 1981. Likewise, these 1 akes provided the 1 ast open water in
fall and were used by the late migrants. Swans used these lakes during
October as other lakes in the region became ice-covered. Between 9 and
11 Trumpeter Swans frequented Murder Lake between 10 and 18 October 1981
(J. Ireland, pers. comm.), 11-22 unidentified swans were on Stephan Lake
from 9 to 23 October J'181, and 120 swans were there on 10 October 1980.
*See Figure 1 for location of specific waterbodies.
55
01
0"1
TABLE 14
SEASONAL POPULATION STATISTICS FOR THE MORE IMPORTANT OF SURVEYED WATERBODIES OF THE UPPER SUSITNA RIVER BASIN, 1960-81. INCLUDED ARE WATERBOOIES
THAT WERE AMONG THE SIX HIGHEST IMPORTANCE VALUE RATINGS IN AT LEAST ONE SEASON.
Fall 1980** Fall 1981** Spring 1981++ Summer 1981
Mean Mean Mean Mean Mean Mean Mean Mean t~ean Density
Size . no. density no • no. density no. no. density no. No. of No. No.
Waterbody (km 2) birds (no./km 2) species birds (no./km 2) species birds (no./km 2) species adults adults species broods
WB 107 0.15 39.0 260.0 4.3 38.0 253.3 3.0 51.3 342.2 5.0 23 153.3 5
(Murder Lake)
WB 106 3.55 156.0 43.9 9.5 168.5 47.5 5.0 99.7 28.1 7.3 87 24.5 9 2
(Stephan Lake)
WB 140 0.90 53.5 59.4 5.0 30.5 33.9 2.5 48.3+ 53.7+ 3.7+ 75 83.3 11 4
WB 131 1.04 212.8 204.6 6.5 123.0 118.3 5.0 54.7+ 52.6+ 3.7+
WB 145 CJoxenct> '-· 1.60 103.8 64.8 7 .o 42.5 26.6 4.5 58.7 36.7 7.0 35 21.9 8 6
_ WB 059 1.44 72.8 50.5 6.5 55.0 38.2 3.0 21.3 14.8 4.7 54 37.5 11 5
WB 148 1.25 95.8 76.6 3.8 34.5 27.6 2.0 21.3+ 17.1+ 3.0+ 8 6.4 3 0
(Watana Lake)
WB 067 0.76 19.0* 17.9* 4.0* 4.0+ 5.3 1.5+ 85.0 111.8 6.0 15 19.7 8 5
(Pistol Lake)
WB 032 0.07 8 114.3 4 6
WB 150 0.57 11.5 20.2 0.5 4.7+ 8.2+ o. 7+ 33 57.9 5 4
( Swirnni ng Bear Lake)
* Combines WB 064-067
** 11, 16, 20, and 26 September 1980; 15 and 26 September 1981
+ 100% frozen on at least one survey
++ 3, 10, and 26 May 1981
--Not surveyed
WB 131, near the mouth of the Maclaren River, was another of the most
important lakes on the study area, because it consistently supported
high levels of waterfowl abundance, density, and species richness. Its
I.V. in spring was lessened by the fact that it was still frozen during
two (3 and 10 May} of the three spring surveys. Because it was so far
from the main proposed construction sites, we did not census it for
breeding birds in"July, but a flight over the lake on 4 August 1981
revealed a flock of some 100 molting ducks, mostly scaup, as well as a
pair of Trumpeter Swans. This and WB 134 were the only duck-molting
lakes we found in the basin. A flock of 22-42 Trumpeter Swans congre-
gated to feed on this lake throughout the first half of September 1980.
WB 140, east of the Oshetna River, had the highest I.V. of the 28 water-
bodies censused during the breeding season. Not only did it have a high
species richness (11 species), but it also supported a large number of
birds and an above average density. It was also of above average impor-
tance during migration, although it thawed late and froze early.
WB 145, Clarence Lake, had the fourth highest I. V. during spring and
fall migration, but was less important during the summer. It had a
relatively high species richness at all seasons, being used by bo~h
. diving and dabbling ducks during migration, but primarily by divers in
summer. A flock of 51 migrant Snow Geese flew west over this lake on
30 April 1981 (T. W. Hobgood, pers. comm.).
WB 148, Watana Lake, was used in fall, especially in 1980, by migrant
scaup, goldeneyes, and mergansers during the last half of September.
Otherwise it was of little importance to birds.
WB 067, Pistol Lake, had a relatiyely high I.V. in spring becaus~ of the
number and diversity of birds it contained after it began to th~w toward
the end of the first week of May. This relatively large lake was only
of average importance during summer, however, and was little used in
fall.
57
WB 059, the southernmost Fog Lake, supported high levels of abundance
and species richness at all seasons. It received less use in spring
than at other seasons, probably because of ice cover, which was still
extensive as late as 17 May 1981. On this date, ducks were heavily
concentrated in the open water at the inlet end of the lake. This lake
and WB 140 had the highest species richness (11 species) during summer.
WB 032, a small lake at the west end of the Fog Lakes, supported a high
density of birds in summer and showed high productivity (at least four
broods of Horned Grebe and two of American Wigeon seen on 28 July 1981).
It was not monitored during migration.
WB 150, Swimming Bear Lake, an alpine lake, received its primary use
during summer. After it thawed in l&te May, it was occupied by' at least
five species of waterbirds (scaup, "Oldsquaw, seater, Mew Gull, and
Arctic Tern), three of which had broods on 29 July 1981. Flocks of
scaup and White-winged Seaters were seen on the lake during the last
half of September 1981.
None of the waterbodies in the upper Susitna River Basin had Importance
Values as high as those calc~lated for some of the better wetland sites
of eastern interior Alaska from data obtained during fall 1980 by
Ritchie and Hawkings (1981) (Fig. 3) and during spring 1980 by Ritchie
{1980) {Fig. 4).
3.5 Breeding by Cliff-nestina Raptors, Ravens 2 and Eagles
(a) Summer Populations
In all, 43 raptorjraven nest sites were located during 1980 and 1981, 20
of which were inactive in both years. Presumably these inactive sites
58
en w
Q
0
al a:
w
1-
c:(
::
0
~
0
UJ
0. en
~
0
en
UJ
::;)
...1
c:(
>
UJ
0 z
c:(
1-a:
0
0.
:E
75~--~---------.-------------.
70
30
25
20
15
10
5
Scottie•Oesper Creek "'S 15,16,17,1'-1 of 20
-----;r-------------;r-----
-----~------------~-----Moon La ka a1 ea
WB 131 •
WB 106 Stephan Lake •
WB 0 59 Fog Lakes.
WB 105
WB 130 Oeaclman lake
WB 135
WB 121•128
Delusion Creek Group
WB 129 Big Lake
Midway Lake
WB 107 Murder Lake
WB 145 Clarence lake
WB 148 Watana lake
WB069
W8064·067
Pistol Lake Group
WB134
WB104
WB 103
~= g~: Fog Lakes
WB 06rr
WB 037 0~----------~----------~
FIGURE 3
Relative importance of 20 waterbodies for migrant
loons, grebes, and waterfowl in the upper Susitna
River Basin, Alaska, compared to 3 waterbodies in
the upper Tanana River-Scottie Creek area of eastern
Alaska in fall 1980;
59
35~--------------~------------~
30 Cathedral Blurt lakes
Quartz Lake
Shaw Creek Flats Moon Lake & Vicinity.
en w 25 -Q
0
a:l a: w ...
-:( WB 107-Mun1er Lake
::
() 20 -Dry Lake
Ll. -u w a. en Dot Lake-sam Crk area
Ll.
0 15
en w
::l
~
-:(
> WB 067• Pistol L aka
w
0 9ear Chief" Creek
z 10
-:( ... a:
0 a.
Robeitson River WB14S-clarence Lake
::i! Johnson Slough
5
FIGURE 4
Relative importance of 34 waterbodies for migrant loons,
grebes, and waterfowl in the upper Susitna River Basin,
Alaska, in spring 1981 compared to 9 waterbodies in the
upper Tanana River Valley of eastern Alaska in spring 1980.
60
function either as alternative sites or are used in year_s of higher
population levels. Of the 23 nests that were active in at least one
year~ at least 5 were used both years, each by the same species (Table
15). Active sites during the two years of study included ten of G:)lden
Eagle, six of Bald Eagle, four of Common Raven, one, perhaps two, of
Gyrfalcon, and one of Goshawk.
In 1974, White (1974) found ten active nests within this same geographic
area: two Gyrfalcon, one Bald Eagle, and seven Common Raven. He reported
14 inactive nests, ascribing 8 to ravens and 3 each to Golden and Bald
eagles. The reason for the substantially different species composition
between the two sets of surveys, i.e., more ravens and fewer eagles in
1974, is unknown.
The concentration of active Gal den Eagle nests in both 1980 and 1981
(one pair per 14.8 km [9.2 miles]) was similar to that along the Dalton
Highway through the Brooks Range in 1979 (one active nest per 15.7 km
[9.7 miles]) (D. G. Roseneau, pers. comm.)--the Brooks Range having one
of the largest populations of Golden Eagles in Alaska. A. Murie (1944),
in Denali (Mt. McKinley) National Park, found active nests as close as
1.6 and 2.4 km (1-1.5 miles) to each other in 1941 and 1939, respectively.
Pairs of Golden Eagles regularly build and maintain a number of simul-
taneous nests, which they use as alternative sites in various years
(Brown and Amadon 1968), some several kilometers apart (D. G. Roseneau,
pers. comm.). It has been suggested (White et al. 1977) that local
populations increase during years of high hare populations, .but hares
were relatively scarce on the upper Susitna in 1980 and 1981. A. Murie
0·944) found that ground squirrels were a major prey of Golden Eagles in
Denali National Park in 1939-1941, and this species was abundant in the
Susitna area during our study.
Bald Eagle densities found in the upper Susitna River drainage appear
slightly lower than those of interior Alaska, where Roseneau et al. (1981)
61
TABLE 15
LOCATION OF ACTIVE RAPTOR AND RAVEN NEST SITES, UPPER SUSITNA RIVER BASIN, ALASKA, 1980 AND 1981, AND THEIR PROXIMITY TO POTENTIAL ADVERSE DISTURBANCE
FROM CONSTRUCTION ACTIVITIES
Substrate
elevation Active Active
Nest Species m (feet) 1980 1981 Nest location
A Bald Eagle 490 (1600) X 0 8,0 km up Susitna River from the mouth of Watana Creek. On
wooded island in live, 15m white spruce.
B Bald Eagle 690 (2260) X
c Golden Eagle 750 (2450) X
D Golden Eagle 700 (2300) X
E Golden Eagle 640 (2100) X
F Golden Eagle 550 (180~) X
G Golden Eagle 490 (1600) X
H Unknown 490 (1600) X
Golden Eagle 3e~ (1200) X
J Raven 520 ( 1700) X
K Bald Eagle (2500) X
L Bald Eagle 275 (900) X
X
0
0
X
0
0
0
X
1
X
X
4.5 km up Oshetna River from its confluence with the Susitna River.
Nest 4 m from edge of west river bank in a 22 m white spruce.
3.5 km upriver from V-Canyon and 0.7 km up a narrow canyon on the
north side of the Susitna River. Nest 26m up a 33m cliff,
100 m back from and 6. 7 m above unnamed creek.
4.0 km up the Susitna River fran the mouth of Jay Creek and in
canyon on north side of the Susitna. Nest 5 m up 13m cliff,
10 m back from and 18 m above unnamed creek.
2.5 km up Jay Creek from its junction with Susitna River. Nest
5 m up 30m cliff, 150m from west bank and 115m above Jay Creek.
1.0 km down Susitna River from the mouth of Kosina Creek. Nest
32m up 38m cliff on north riverbank.
4.0 km down Susitna River from the mouth of Watana Creek. Nest
13m up 23m cliff, 40 m back from and 34m above the north
bank of the river.
6.8 km down Susitna River from mouth of Devil Creek and 4.0 km up
a gorge on south side of the Susitna. Nest 100 m up 105 m cliff
of creek canyon. Occupied by a Gyrfalcon in 1974 (White 1974).
0.5 km up Devil Creek from its mouth. Nest 30m up 45 m
vegetated cliff, 100m back from and 120m above Devil Creek,
on west bank.
1.0 km up Devil Creek from its mouth. Nest near top of
cliff of west bank. Could not relocate nest in 1981.
9.0 km up Deadman Creek from its mouth. Nest on top of 15m
broken-topped cottonwood, 25 m from north side of Deadman Creek.
1.0 km up Susitna River from confluence with Indian River.
Nest on top of 23m broken-topped Cottonwood, 4 m frrnn north
river bank.
Potential disturbance
Inundation
Inundation
Inundation
Inundation
0.5 km from road and rail-
road, east end Corridor 2*
Inundation
Approximately 50 m from
Corridor 3
0.5 km from road and rail-
road, west end Corridor 2*
TABLE 15 (Continued)
Substrate
elevation Active Actfve
Nest Specfes m (feet) 1980 1981
H Golden Eagle 305 (1000) X
N Bald Eagle 580 ( 1900) X
0 Raven 470 (1550) X
p Raven 550 ( 1600) X
Q Raven 625 (2050) X
0"1 w R Golden Eagle 975 (3200) X
s Bald Eagle 540 (1775) 0 X
T Golden.Eagle 685 (2250) 0 X
u Gyrfalcon 715 (2350) X
v Golden Eagle 750 (2450) 0 X
00 Goshawk 550 (1800) X
0 .. inactive
-a site not located in 1980
Nest location
2.0 km up Susitna River from the mouth of Portage Creek.
Nest on moderate-sized cliff on north bank, but not relocated
on ground check.
On south shore of WB 105, 1.0 km east ·Of NE end of Stephan
Lake. Nest on top of 13 m broken-topped cottonwood.
2.0 km up Fog Creek from mouth. Nest 9 m up 23m cliff on
west bank, 17 m back from and 23 m above creek.
5.0 km up Tsusena Creek from mouth. Nest on cliff on east
bank of creek.
1.0 km up Deadman Creek from mouth. Nest 13m up 32m cliff
on east bank of creek.
8.0 km down Susitna River from the mouth of Kosina Creek.
Nest 7 m up 12m cliff on tor above south bank of river.
2.0 km up Susitna River from the mouth of Kosina Creek.
Nest 25m up 33m cliff on north bank of river.
4.0 km up Susitna River from the mouth of Jay Creek, in
canyon on north side of river. Nest 1 m up 5 m vegetated
cliff, 14m back from and 33m above unnamed creek.
At V-Canyon. Nest 100m up 113m cliff at south bank of
Susitna River.
3.5 km up Susitna River from V-Canyon and 0.7 km up narrow
canyon on north side of Susitna River. Nest B m up 12m cliff,
81 m back from and 67 m above unnamed creek.
2.0 km southeast of Devil Canyon Drun site.
*a east and west ends.of Corrfdor 2 divided at Devil Canyon dam site
Potential disturbance
On alternate b of road and
railroad, east end Corridor 2
0.7 km from alternate b of
road and railroad, east end
Corridor 2
0.5 km from road. east end
Corridor 1
Inundation
I nunda tfon
Inundation
100 m from road and 200 m
from rail road, east end of
Corridor 2
reported 44 nests, 25 active in 1980, in the vicinity of the Alaska
Highway and Tanana River between Fairbanks and the U. S.-Canada border,
a distance of approximately 480 km (300 miles).
Compared to eagles, Gyrfalcons are uncommon in central Alaska, but they
nest throughout the Alaska Range. Cade (1960) estimated the total
Alaska population at about 200-300 pairs, whereas Roseneau et al. (1981)
thought there were more, but fewer than 500 pairs. Numbers in a giyen
area may vary considerably between years (Cade 1960, Roseneau 1972), but
probably not over large geographic regions (Roseneau 1972). Gyrfalcons
in northern and western Alaska have low site fidelity from year to year
(Cade 1960, Roseneau 1972), but in the Alaska Range most sites are used
every year (Bente 1981).
There were no confirmed sightings of Peregrine Falcons in the region
during our study, in spite of the many hours spent in ornithological
field work and in raptor habitat. White (1974), however, saw two indi-
vidual Peregrines during his 10-15 June 1974 survey, but found no sign
of nesting. One bird was a 11 Single adult male ••• roosting on a cliff
about 4 mi'l es upriver from the Devil Canyon Dam axis, 11 and the other was
11 a sub-adult ••• about 15 miles upriver from the Devil Canyon Dam axis. 11
White (ibid.) stated that the Yentna-Chulitna-Susitna-Matanuska drainage
basin 11 seemingly represents an hiatus in the breeding range of breeding
peregrines ••• , 11 and Roseneau et al. {1981) stated that 11 The Susitna and
Copper rivers both provide ••• [very few] ••• potential nesting areas for
. Peregrines."
A single observation o.f an Osprey was' reported during the two seasons of
study, a bird seen on 23 May 1981 by J. Ireland at Murder Lake (pers.
comm.).
64
(b) Breeding Chronologies
No special effort was made to obtain data on the breeding biology of
raptors and ravens on the Susitna study area. Because the breeding
season is a period when most birds are relatively sensitive to distur-
bance, however, we show in Table 16 the breeding chronologies of eagles,
Gyrfalcon, and Common Raven in interior Alaska.
(c) Potential Disturbance Factors
The general types of impacts on raptors that can result.from development
activities have been well-described by Roseneau et al. (1981), and
Tables 17-19, which summarize disturbance factors, are taken from their
report.
Inundation is an additional potential impact from hydroelectric pro-
jects. In the upper Susitna River Basin, the total length of good
potential raptor cliffs (type "A") that would be inundated by the pro-
posed rese1rvoirs is 42.5 km (26.4 miles) (Table 20). Almost all 11 A11
quality habitat in the Watana reservoir will be inundated, but only
about half of that in the Devil Canyon reservoir. Currently, however,
the number of raptor nests (active and inactive) is considerably greater
in the proposed Watana reservoir area than in that for Devil Canyon dam
(Table 21), with densities of 0.6 nest sites/km and 0.1/km, respec-
tively. For some reason, in spite of cliffs with good structural char-
acteristics, Devil Canyon is little used for raptor nesting. Possibly
the deep, narrow canyon, with its often strong and buffeting winds,
makes this area undesirable for raptors.
3.6 -Avifauna/Habitat Relationships
A general overview of bird habitat preferences in the upper Sus.itna
River Basin can be obtained by examining the density of territories of
65
TABLE 16
BREEDING CHRONOLOGIES OF EAGLES, GYRFALCON, AND COMMON RAVEN IN INTERIOR ALASKA
OATES OF PHASES OF. BREEDING CYCLE
Species Status + Arrival/courtship Egg-laying Incubation Nestlings Fledging/dispersal
Golden Eagle* M 5 Mar-30 Apr 1 Apr-10 May 15 Apr-20 June 1 June-1 Sept 1 Aug-25 Sept
Bald Eagle* M/R 10 Mar-l May 20 Mar-10 May 31 Apr-30 June 20 May-15 Sept 1 Aug-30 Sept
0\ Gyrfalcon* R 1 Mar-lO Apr 1 Apr-20 May 5 Apr-25 June 15 May-15 Aug 10 July-30 Sept 0\
Raven** R 1 Mar-15 Apr 1 Apr-5 May 5 Apr-25 May 25 Apr-25 June 25 May·l5 July
+ M • migrant, R = resident
* Data summarized from Roseneau et al. (1981)
**Based on calculations from Kessel (unpubl. data) and Brown (1974)
TABLE 17
GENERAL TYPES OF IMPACTS TO RAPTORS (FROM ROSENEAU ET AL. 1981)
Disturbance
Construction and Operation Activities
sudden laud noises (e.g., blasting, gas venting, etc.) can lead to panic flights
and damage to nest contents
-noise, human presence, etc. can lead to disruption of daily activities
Aircraft Passage
-sudden appearance and noise can lead to panic flights and damage to nest contents
Human Presence Near Nests
-inadvertent -chance occurrence of people (and dogs} near nests; people may be
unaware of nest, raptors, or raptor alarm behavior
-deliberate-curious passersby, naturalists, photographers, researchers can have
·impacts if safeguards are not taken
Direct Impacts
Intentionally Destructive Acts (as a result of increased public access)
-shooting
-legal or illegal removal of eggs, young, or adults
-rolling of rocks off cliff tops
-cutting of nest trees
Man-made Structures and Obstructions
-raptors may be struck on roads where they may perch or feed
-n~y strike wires, fences, etc.
-may be electrocuted on power poles
-raptors sometimes attack aircraft, or may accidentally strike aircraft
Environmental Contaminants
-deliberate application and accidental release of insecticides, herbicides, petro-
chemicals, and toxic industrial materials can affect raptors and prey by affecting
hormones, enzymes, shell thickness, bird behavior, egg fertility and viability, and
survival rates of nestlings, fledglings, immatures and adults
Changes in Prey Availability
-decrease in prey abundance or loss of nearby hunting areas may affect territory
size, efficiency of hunting, nest occupancy, nesting success, condition of adults
and young
-changes may result from aircraft overflights, construction and maintenance activi-
ties, public access, etc.
Habitat Loss
Abandonment of area due to destruction of nest, perch or important hunting habitat
67
TABLE 18
FACTORS THIAT AFFECT THE SENSITIVITY OF RAPTORS TO DISTURBANCES (FROM
ROSENEAU ET AL. 1981)
Characteristics of the disturbance
-type of disturQance
-severity (speed, loudness, suddenness, persistence, etc.)
-frequency of occurrence
Characteristics of the bird
the individual (individual differences in response)
-sex
-age
•mood• (a factor of recent activities, weather)
-territorial status (breeder, territorial non-breeder, or non-
territorial floater)
-stage of annual life cycle (winter, migration, courtship, egg-
1 ay·i ng, rearing young, etc.)
-occurrence of other disturbances or natural stresses at the same
time
-previous experience with this type of disturbance (habituation may
occur)
Topography
-nearness of disturbance to raptor or nest
-relative elevations (is nest or raptor above or below the distur-
bance? by what distance?)
-presence of screening features (trees, intervening hill)
-direction faced by nest relative to sun, wind, disturbance
-type of nest (exposed ledge, overhung ledge, cave)
-distance of nest above foot of cliff and below lip of cliff (i.e.,
•security• of nest)
Time of day
Weather at time of disturbance
Potential predators nearby
Type of prey utilized by the bird {species, location, abundance)
68
TABLE 19
INFLUENCE OF TIMING OF DISTURBANCE ON THE POSSIBLE EFFECTS ON RAPTORS
(FROM ROSENEAU ET AL. 1981}
Timing
Winter
Arrival and
courtship
Egg-laying
Incubation
Nestling
phase
Fledgling
phase
Night
General
Possible effects of disturbance
Raptor may abandon nest, roosting cliff, or hunting area
(e.g., Gyrfalcon)
Migrant raptor may be forced to use alternative nest
site (if available), may remain but refuse to breed or
may abandon nest site
Partial clutch may be abandoned and remainder (or full
clutch) laid at alternative nest; breeding effort may
cease or site may be abandoned
Eggs may be chilled, overheated, or preyed upon if
parents are kept off nest too long; sudden flushing from
nest may destroy eggs; male may cease incubating; clutch
or site may be abandoned ·
Chilling, overheating, or predation of young may occur
if adults are kept off nest; sudden flushing of parent
may injure or kill nestlings; malnutrition and death may
result from missed feedings; premature flying of nest-
1 ings from nest may cause injury or death; adults may
abandon nest or site
Missed feedings may result in malnutrition or death;
fledglings may become lost if disturbed in high winds;
increased chance of injury due to extra moving about;
parents may abandon brood or site.
Panic flight may occur and birds may become lost or
suffer injury or death
Undue expense of energy; increased risk of injury to
alanned or defending birds; missed hunting opportunities
69
TABLE 20
LINEAR DISTANCES OF CLIFFS IN VICINITY OF PROPOSED IMPOUNDMENTS, AND
DISTANCES THAT WOULD BE INUNDATED, SUSITNA HYDROELECTRIC PROJECT
Length above
Type of Length inundated waterline
cliff ( km) ( km)
Devil Canyon Reservoir
A 27.4 24.9
B 8.3 7.9
c 2.4 1.6
Watana Reservoir
A 15.1 0.9
B 5.1 0
c 1.6 0.3
70
"'-J ......
TABLE 21
NUMBER OF KNOWN RAPTOR OR RAVEN NEST SITES IN UPPER SUSITNA RIVER BASIN, ALASKA, THAT WOULD BE INUNDATED BY DEVIL
CANYON AND WATANA RESERVOIRS
----·--
Spec1es
Golden Eagle
Bald Eagle
Gyrfalcon
Gosha1~k
Common Raven
Unknown
TOTALS
Total no.
active nests
10
6
1
1
4
1
23
Total no.
fnactfve nests
9
1
0
0
1
3
20
Active nests that
would be flooded
Devil canyon Watana
1 4
0 2
0 0
0 0
1 0
0 0
2 6
Inactive nests that
would be flooded
Devil Canyon Watana
2 3
0 1
0 0
0 0
1 2
0 0
3 6
Total flooded
nests
10
3
0
0
4
0
17
various species in the habitats represented by the bird census plots
(Table 9), the assumption being that species occur in greatest densities
in their preferred habitats. Similarily, some information on habitat
preferences was obtained from our general surveys, in which we recorded
the number of individuals of each species seen per kilometer in various
habitats (data not shown).
Following, based on data from the bird censuses and the general bird
surveys, is a list of the four or five most abundant species found
during the summer in each of the major avian habitats of the upper
Susitna River Basin:
(a) Lacustrine Waters and Shorelines: Arctic Tern, Hew Gull,
Lesser and Greater scaup, Common Loon.
{b) Fluviatile Waters, shorelines, and alluvia: Spotted Sand-
piper, ~1ew GuJl, Violet-green Swallow, and Harlequin Duck.
(c) Upland Cliffs and Block-fields: Gray-crowned Rosy Finch,
Common Redpoll, Horned Lark, American Golden Plover, Water
Pipit.
(d) Dwarf Shrub Mat: Water Pipit, American Golden Plover, Horned
Lark, Lapland Longspur, Rock Ptarmigan.
{e) Low Shrub: Savannah Sparrow, Tree Sparrow, Lapland Longspur,
~lh i te-e rown ed Sparrow.
(f) Medium Shrub: Tree Sparrow, White-crowned Sparrow, Savannah
Sparrow~ Arctic Warbler, Wilso-.'s Warbler.
(g) Tall Shrub: Hermit Thrush, Wilson's Warbler, Fox Sparrow,
White-crowned Sparrow, Tree Sparrow.
72
(h) Scattered Woodland and Dwarf Forest: White-crowned Sparrow,
American Robin, Bohemian Waxwing, Tree Sparrow, Ruby-crowned
Kinglet.
(i) Mixed Deciduous-Coniferous Forest: Hermit Thrush, Dark-eyed
,Junco, Yellpw-rumped Warbler, Swainson's Thrush, Varied
Thrush.
(j) Deciduous Forest: Yellow-rumped Warbler, Common Redpoll,
Swainson's Thrush, Blackpoll Warbler.
(k) Coniferous Forest: Ruby-crowned Kinglet, Varied Thrush,
Dark-eyed Junco, Yellow-rumped Warbler, Swainson 's Thrush.
A more detailed examination of species-specific habitat selection during
the breeding season, based on the more than 60 habitat variables
measured on the 588 subplots (Table 1), is still incomplete because of
time constraints. A principal component analysis was performed, however,
using 31 structural habitat variables that were present across
the full range of the 12 bird census plots, i.e., from tundra through
forests. This procedure provided statistically uncorrelated axes
(principal components), each representing a combination of habitat
characteristics, along which to ordinate each bird census plot (using
mean factor scores from each plot's 49 subplots) (not shown) and to
ordinate the habitat data for individual b·ird species (using mean factor
scores from subplots on which the species was recorded at least once
during the eight 1981 censuses} (Fig. 5).
An examination of how each habitat variable ••loaded" onto each of the
first four principal components allowed an interpretation of ~he meaning
of these axes. PC I corresponded to a gradient of openness, ranging
from open treeless to heavy-canopied habitats, a primarily deciduous
component; it accounted for 33.8% of the total variation (information)
73
PC
-1.0
THICK, 1.0
DENSE BHRUBBEIIYI
MOll
o.s
0
GTH
PC Ill -0.5 RCK
wcs WWR JAY FOX TSP AIIC
JCO BPW 80R
-1.0 STH VTH NWT
CRP YRW SGR HTH
~lSS IHRUBBEIIYI BCR
liCHEN$ -1.5 SAY BCC
/ / / / I \ \ y '\ " ....... LARGE CONIFERS; ......... 1_7 / / / / 7 I \ \ ~" ........ ' l.ESS SHRUBBERY I
') >/ ""-DWARF SHRUB,
II O 5 LAP I I I \ K" '\. '\. "'
MOSS
/ 7 / / / I 7 I \ '\ \. " 1"-.. "' 7 / / I I I \ \ \ \. " "' '-.... TRE
/ / / L I I I \ \ _\ " ' " ~· -1.25 -1.00 -0.75 -0.50 •0,25 0 0.25 0,50 0.75 1.00 1,25 1.50 1.75
NO CANOPY, TREELESS;
DWARF SHRUB, MOSS, LICHEN
PC I
HEA~Y CANOPY, ~ARGE TREES;
MEDIUM•TALI,. SHRUBS;
LITTER, FORB, GRASS
FIGURE 5
Habitat ordination of 22 bird species ~n the upper Susitna River Basin, Alaska, based on a three-
dimensional plot of mean factor scores from subplots on which the species occurred at least once
during 1981 censuses (LAP = Lapland Longspur, SAV = Savannah Sparrow, TSP = Tree Sparrow,
ARC ; Arctic Warbler, WCS = White~crowned Sparrow, RCK =·Ruby-crowned Kinglet, WWR = Wilson's
Warbler, JAY = Gray Jay, GTH = Gray-cheeked Thrush, FOX = Fox Sparrow, JCO = Dark-eyed Junco,
BPW = Blackpoll Warbler, CRP =Common Redpoll, BOR =Boreal Chickadee, YRW = Yellow-rumped Warbler,
STH = Swainson's Thrush, SGR = Spruce Grouse, HTH = Hermit Thrush, BCR = Brown Creeper,
VTH = Varied Thrush, NWT = Northern Waterthrush, BCC = Black-capped Chickadee).
ELESS;
GH SHRUB CANOPY!
GRASS, SEDGE, LITTER
in the data set. PC II, which accounted for 10.6% of the variation,
1 inearly combined two relatively independent habitat gradients, one
ranging from treelessness to woodlands and forests with conifers, and
the other from high deciduous shrub canopy ( ta 11 and med i urn shrubs,
primarily alder) to less shrubbiness. PC III corresponded to thickness
and density of shrub cover and _accounted for 8.8% of the variation.
PC IV represented a substrate moisture gradient, ranging from bare soil
and lichens to low shrubs with a ground cover of forbs, grasses, sedges,
and water, a!ld accounted for. 7.0% of the variation. In all, 60.2%'of
the variation in the data set was accounted for by these four principal
components.
The ordination of the habitat data for 22 bird species along the first
three principal components is shown in Figure 5. The height of each
vertical bar represents the factor score along PC III, whereas the dot
at the bottom of the bar shows the species' ordination relative to PC I
and II. Although this ordination presents some problems of interpreta-
tion that have yet to be addressed, the species on the left end (-) of
PC -I were selecting treeless habitats with varying amounts of shrubbery;
those on the right(+), forest habitats; and those in the middle, either
open forests (Ruby-crowned Kinglet and Gray Jay) or medium-tall shrub-
bery that may or may not have a forest overstory. The Northern Water-
thrush is in an anomalous position along this axis, reflecting the
phytogeography of the region. Generally, the species favors tall shrub
thickets near water (Kessel, pers. obs.). This habitat occurred almost
entirel~ along the major rivers at the lower elevations of the Susitna
River Basin, at the same sites-where the major forests were found. Six
of the nine Northern Waterthrush territories found in 1981 were on the
Cottonwood Forest plot and 2.5 were on the Mixed I plot, both adjacent
to fluviatile waters. Thus, habitat data from the subplots on which
Northern Waterthrushes occurred manifest this riverine association in
the region of tall shrub and forest habitats.
75
Interpretation of species• habitat ordinations along PC II is more
difficult, because the two trends of habitat characteristics combined in
this component influence bird distribution differently. The Hermit
Thrush falls at the lower (-) end of PC II because of its apparent
selection of habitats with high importance values of medium-tall alder
shrubs (cf Table 9 and Table 2). Other bird species at this end of the
axis were selecting treeless habitats. At the upper end (+) of PC II,
Gray Jays appear to have been selecting habitats with large spruce
trees. An understanding of the positioning of the other species along
this composite axis must await application of further statistical
procedures, however.
Along PC III, the Lapland Longspur (shortest vertical bar) shows selec-
tion of open habitats; in actuality, it often occurred where only a
ground cover of prostrate, dwarf shrub was present. Species with the
tallest bars (Gray-cheeked Thrush and Fox Sparrow} were birds of the
tall shrubs, which in this area were primarily alders or short spruce,
both of which have thick (deep) canopies and also often grow in associa-
tion with shrubbery of lower-height canopies. Other species with tall
bars (Arctic Warbler, Tree Sparrow, and White-crowned Sparrow) show
their selection of habitats with dense, low-and medium-height shrub
birch. The Wilson's Warbler occurred in both types of shrub habitats,
with or without a forest canopy.
3.7-Annotated List of Species
-
A list of the 135 species of birds recorded in the upper Susitna River
Basin during the study, with species-specific information for the region
(abundance and status, habitat, phenological data), follows. Infonna-
_tion for th9se species accounts was drawn from above Sections 3.1-3.6
and from tne collective field observations gatht:red by our group and
others throughout the study. Breeding by some birds in the study area
has not yet been confirmed. In the annotated list, a species is called
76
a breeder only if we have a substantiated breeding record. Suspected
breeding--based on such things as breeding or territorial behavior of
adults, breeding status in closely adjacent areas, or persistent
abundance of certain species in breeding habitats--is indicated as
"probable" or "possible" breeding, depending on the strength of the
evidence.
Common Loon. Gavia immer. Uncommon breeder on lacustrine waters.
Species occurred 16 May (1981) through 19 October (1981). Four
birds each on 26 May 1981 and on 20 September 1980 was maximum day
count. Three broods totaling five young were seen 28-29 July
1981; the oldest chick was about two-thirds adult size, with
juvenal feathering in the dorsal and scapular feather tracts.
Arctic Loon. Gavia arctica. Uncommon spring migrant and probable
breeder on lacustrine waters. Species was observed from 16 May
(1981), when a dead bird was found on a pond just north of Watana
Camp, through 27 July (1981), when a pair was observed on WB 015.
A total of 12 birds was seen in 1981.
Red-throated Loon. Gavia stellata. Uncommon probable breeder on
lacustrine waters, occurring between 9 May (1981) and 21 August
(1980). Few birds were seen, six in 1980 and 12 in 1981.
Red-necked Grebe. Podiceps grisegena. Uncommon breeder on lacustrine
waters, occurring from 16 May (1981) through 12 October (1981),
maximum eight birds on 15 September 1981. An adult flushed from a
nest north of Watana Camp on 18 July 1980, and a pair with two
juvenal-feathered, non-flying young was on WB 036 on 27 July 1981.
77
Horned Grebe. Podiceps auritus. Uncommon breeder on lacustrine waters.
Species occurred 10 May (1981) through 3 October (1980), maximum
17 birds on 16 September 1980. Five broods totaling eight large
downy young were seen on 28 July 1981; four broods were on WB 032
and the other was on WB 033.
Whistling Swan. Olor columbianus. Fairly common migrant. Two birds
on 9 May 1981, 14 on 17 May 1981, and two on 22 May 1981 were the
only records in spring. The first Whi~tling Swans ide~tified in
fa 11 were 18 birds on WB 134 on 26 September 1981. Others (up to
23) were identified at WB 103 and WB 104 on 8-9 October 1981. The
144 swans reported by George Nissen, helicopter pilot, on Stephan
Lake and nearby WB 105 on 10 October 1980 were probably also
mostly Whistling Swans, based on the size of the aggregations and
the fact that they occurred during the known period of peak move-
ment of this species through central Alaska (Kessel, unpubl.
data).
Trumpeter Swan. Olor buccinator. Common breeder on lacustrine
waters, especially in the wetlands east of the Susitna, between
the Oshetna and Maclaren rivers. Earliest in spring was a sighting
on 29 April 1981 on Murder Lake by J. Ireland; he also reported
7-11 Trumpeters there between 10 and 18 October 1981, the latest
birds identified as this species. However, small groups of swans,
composed of 6-13 adults and juvenals, on Stephan Lake between 20
and 23 October 1981, were probably of this species. Maximum count
was 42 Trumpeters on WB 131 on 7 September 1980. Single pairs
were at their nests on WB 132 and WB 138 on 26 May 1981. Nine
broods (2-5 cygnets each) were counted during a 1~-hour random
survey over the ponds of the Oshetna-Maclaren region on 4 August
1981.
78
Canada Goose. Branta canadensis. Uncommon migrant. In spring this
species occurred from 20 April (1981) to 18 May (1981), maximum
35 birds on 1 May 1981. It was observed in fall from 16 August
{1980) to 22 October (1981); high count was 27 flying over Watana
Creek on 23 September 1981.
White-fronted Goose. Anser albifrons. Uncommon spring migrant. Six
birds seen 1 May 1981 at Watana Camp Lake constituted the only
record.
Snow Goose. Chen caerulescens. Uncommon spring migrant. The only
record was of 51 birds seen flying over Clarence Lake by T. W.
Hobgood on 30 April 1981.
Mallard. Anas platyrhynchos. Common spring and fairly common fall
migrant and uncommon breeder on lacustrine waters. Species
·occurred from 23 April {1981) to 19 October {1981), with the main
fall passage occurring from late September to mid-October. Maxi-
mum count in spring was 121 birds on 26 May 1981 and in fall 153
birds on 26 September 1981. Single broods were seen on 13 July
1980 and 27 July 1981, the latter of four flying juvenals.
Gadwall. Anas strepera. Rare spring migrant and summer visitant. A
male at Pistol Lake and a pair at WB 059, all 17 May 1981, and a
male on WB 032 on 3 July 1981 provided the on1y records in the
study area.. This species is nonnally scarce north of the Pacific
coast of Alaska (Kessel and Gibson 1978).
Pintail. Anas acuta. Common spring an~ uncommon fall migrant and
uncommon breeder on lacustrine waters. Pintai1s were recorded
from 24 April (1981) to 3 October (1980), with the main fa11
passage over by mid-September. Spring maximum was 116 birds on
79
26 May 1981, and high count in fall was 60 birds on both 7 and
11 September 1980, all during aerial surveys. Two broods were
found in 1981, one on 8 July and the other, of nearly-fledged
juvenals, on 29 July.
Green-winged Teal. Anas·crecca. Fairly common spring migrant and
uncommon breeder and fall migrant on lacustrine waters. Species
occurred from 29 April (1981) through 3 October (1980), although
the main fall exodus occurred by mid-September. Maximum count in
spring was 67 birds on 3 May 1981, in fall 83 birds on 16 September
1980. Single broods of 2-to 3-week-old chicks were recorded on
12 July 1980 and 8 July 1981.
Blue-winged Teal. Anas discors. Rare migrant. In spring two birds
were seen at WB 067 on 6 May 1981, and one \lfas seen at ~\urder Lake
on 25 May 1981 by J. Ireland. In fall one male at Stephan Lake on
11 September 1980 was the only record.
Northern Shoveler. Anas clypeata. Uncommon migrant and breeder on
lacustrine waters. Species was recorded from 9 May (1981) to
16 September (1980). Maximum count in spring was 28 birds on
26 May 1981, in fall 20 birds on 16 September 1980. A brood of
six downy young seen on 12 July 1981 on Murder Lake was the only
evidence of breeding.
American Wigeon. Anas americana. Fairly common migrant and breeder on
1 acustrine waters. Species occurred from 2 May (1981) through
19 October (1981). The main fall passage occurred during the
first half of September, with a maximum single-day count of 325
wigeon on the aerial survey of 16 September 1980; maximum count in
spring was 102 on the aerial survey uf 26 May 1981. Six broods of
downy young were seen 13-28 July 1981, and a brood of ten large
young was noted on 2 September 1980.
80
Redhead. ~ythya americana. Uncommon spring migrant. The only records
were of 31 Redheads seen in spring 1981. Three birds were seen on
17 May on WB 059, Fog Lakes. The rest were observed during the
aerial survey of 26 May: eight birds on WB 067 (Pistol Lake),
seven on WB 106 (Stephan Lake), two on WB 130 (Deadman Lake),
three on WB 148 (Watana Lake), and eight on WB 145 (Clarence
Lake).
Ring-necked Duck. Aythya col1aris. Rare migrant on lacustrine waters.
The only records were of two birds on WB 059 on 16 September 1980,
a group of seven males and five fe~ales on Clarence Lake on
20 September 1980, and two birds seen on Murder Lake in early May
1981 by J. Ireland.
Canvasback. Aythya valisineria. Uncommon spring migrant. One bird on
WB 067 on 6 May 1981, one on WB 037 on 10 May 1981, and a pair at
WB 059 on 17 May 1981 were the only records in the study area.
Greater Scaup and Lesser Scaup. Aythya marila and Aythya affinis. ·common
migrants and breeders on lacustrine waters. Although both species
were identified, it was often impossible to separate them under
many field conditions; thus they are treated together. Scaup
occurred from 9 l~ay (1981) through 19 October (1981); their main
fall passage occurred during the second and third weeks of
September. Maximum count in spring was 513 birds on 26 May 1981,
in fall 499 on 16 September 1980. Four broods of downy Lesser
Scaup, totaling 14 young, were seen between 16 and 28 July 1981;
three broods totaling 29 young were seen at Stephan Lake on
21 August 1980. Although Greater Scaup were present throughout
the summer, no brooo-were found; they were somewhat less numerous
in.summer than Lesser Scaup.
81
Common Goldeneye and Barrow's Goldeneye. Bucephala clangula and
Bucephala islandica • Fairly common spring migrants and uncommon
breeders and fall migrants on lacustrine and fluviatile waters.
Both species were identified and Barrow's appeared to be more
numerous, but females and eclipse males were usually impossible to
identify to species during summer and early fall, so the species
are treated here together. Goldeneyes occurred from 29 April
(1981) (Barrow's Goldeneye at mouth of Watana Creek) through
17 October (1981) (12 unidentified goldeneyes on Stephan Lake).
Maximum in spring was 51 goldeneyes on 10 May 1981; maxima in fall
were 133 birds on 3 October 1980, 125 on 26 September 1981, and
124 on 20 September 1980. One brood of three downy Common Goldeneyes
was seen on WB 060 (Fog Lakes) on 27 July 1981.
Bufflehead. Bucephala albeola. Uncommo~ spring migrant and fairly
common fall migrant on lacustrine waters. Species occurred in
spring from 29 April (1981) to 26 May (1981) and in fall from
8 September {1981) to 19 October {1981). Maximum count in spring
was 10 birds on 26 May 1981, in fall 127 birds on 26 September
1980, both during aerial surveys. None was recorded in summer.
Oldsquaw. Clangula hyemalis. Fairly common spring migrant and breeder
and uncommon fall migrant on lacustrine waters. Species occur,red
17 May {1981) to 12 October {1981), maximum 84 birds during the
aerial survey on 26 May 1981. Oldsquaws and Black Seaters were
the most productive waterfowl on the study area, with 0.54 broods/km 2
of wetlands surveyed during July 1981~ Eleven broods, mostly
downy young, were counted between 8 and 28 July 1981, three broods
each on Pistol Lake (WB 067), Clarence Lake (WB 145), and WB 140.
Harlequin Duck. Histrionicus histrionicus. Fairly common breeder on
suitable fluviatile waters. Species occurred from 13 May (1981)
through 24 September 1981 and 2 October 1980; maximum single-day
82
count was seven adults in the vicinity of Kosina Creek on 2 June
1981. A few-day-old downy was found dead on Kosina Creek on
17 July 1980, and a brood of four was seen on the Susi tna River
above the mouth of Watana Creek on 25 July 1980.
White-winged Seater. Melanitta deglandi. Uncommon migrant and summer
visitant on lacustrine waters. This seater occurred from 26 r~ay
(1981) to 17 October (1981), maxima 16 birds on 26 May 1981' and 39
on 29 September 1981. A flock of up to 63 birds was present at
Stephan Lake 12-16 July 1981.
Surf Seater. Melanitta perspicillata. Uncommon migrant and breeder on
lacustrine waters. Species occurred 17 May (1981) to 12 October
(1981). Maximum count in spring was 37 birds on 26 May 1981, in
fall 29 birds on 12 October 1981. Two broods of downy young were
recorded on the Fog Lakes on 27 and 28 July 1981. A flock of 12
Surf Seaters, mostly males, was on Watana Lake on 13 July 1980.
Black Seater. Melanitta nigra. Fairly common migrant and breeder on
lacustrine waters. Species occurred 17 May {1981) to 12 October
(1981). Maximum counts were during aerial surveys: 38 birds on
16 September 1980 and 30 birds on 26 May 1981. It was one of the
most productive ducks on the study area (0.54 broods/km 2 of
wetlands). Eleven broods totaling 55 downy young were recorded
between 24 and 29 July 1981.
Common Merganser and Red-breasted Merganser. r~ergus merganser and
Mergus serrator. Uncommon migrants and breeders. Common
· Mergansers may have bred along the Susitna River proper, where we
regularly saw adults off our camps at the mouth of Kosina Cree~
and off the Mixed II plot; Red-breasteds occupied lacustrine and
smaller fluviatile waters in the study area. Because of diffi-
culties in identification from aircraft, these species are
83
discussed together. They occurred from 4 May 1980 and 8 r~ay 1981
(Red-breasted Merganser) and 7 May (1981) (Common Merganser)
through 12 October (1981) (Common Merganser). Maximum count was
68 mergansers (sp .. } on 26 September 1980. Three broods of Red-
breasted Mergansers were recorded: one of six young on Portage
Creek on 23 July 1980, one of four young at High Lake on 5 August
1980, and one of ten newly-hatched young on WB 023 on 6 July 1981.
Molting Red-breasted Mergansers were observed using the wetland
system west of Deadman Mt. and upper Deadman Creek on 3 and
28 July and 24 August 1981.
Goshawk. Accipiter gentilis. Uncommon resident and breeder in decid-
uous and mixed forests. A nest with at least one large young was
found 6 m up in a birch tree, in paper birch forest, 27 July 1981.
Sharp-shinned Hawk. Accipiter striatus. Uncommon probable breeder in
mixed and coniferous forests. Three birds were seen in 1980 and
two in 1981.
Red-tailed Hawk. Buteo jamaicensis. Uncommon migrant; uncommon breeder
in coniferous or mixed forests, occurring from 26 April {1981)
through 16 September (1980}. A pair was seen about a nest on the
Susitna River near the mouth of Portage Creek on 1 May 1981 but
not subsequently. Both !·i· harlani and !·i· calurus were seen.
Golden Eagle. Aguila chrysaetos. Fairly common breeder on cliffs.
Observed 20 April (1981). through 19 October (1981) in the study
area, and a bird was reported in the northern foothills of the
Alaska Range on 20 March 1981 (Kessel, unpubl. notes). Six pairs
nested along the upper Susitna River and its tributaries each
year, using a total of ten ne~t sites during both years. Young
birds ranged from almos·t 3 weeks old to over 4 weeks old at the
time of the aerial survey on 6 July 1980.
84
Bald Eagle. Haliaeetus leucocephalus. Uncommon breeder. Species was
recorded from 10 March (1981) through 30 October (1980). A pair
was observed at a cliff nest near the mouth of Kosina Creek on
28 April 1981. Four active aeries were found in the study area in
both 1980 and 1981; three nests failed in 1981. One nest con-
tained 5-week-old young on 6 July 1980. Nests were in the tops of
cottonwoods and white spruce trees and on riverine cliffs.
Marsh Hawk. Circus cyaneus. Fairly common migrant; uncommon probable
breeder in meadows, occurring as early in spring as 25 April
(1981) and as late in fall as 16 September (1981).
Osprey. Pandion haliaetus. Rare spring migrant. One bird seen at
Murder Lake on 23 May 1981 by' J. Ireland was -the only record in
the studyarea.
Gyrfalcon. Falco rusticolus. Uncommon resident and breeder on cliffs.
One aerie in V-Canyon was occupied in 1981. White (1974) found
two active nests in steep draws on the south side of the Susitna
River, just above the proposed Devil Canyon dam site, 10-15 June
1974. The species is known to occur in the Alaska Range during
winter (Bente 1981), and two were seen near the mouth of Watana
Creek on 11 March 1980.
Merlin. Falco columbarius. Uncommon probable breeder in scattered
woodland and forest edge. Ten birds were recorded in 1980, but : .. ~
only three in 1981. A pair exhibited defensive behavior at
Deadman Falls Canyon on 5 June 1981, and a bird was seen there
again on 28 July 1981.
American Kestrel. Fil co sparverius. Rare fall migrant. One male at
Stephan Lake on 23 August 1980 was the only record.
85
Spruce Grouse. Canachites canadensis. Fairly common resident and
breeder in mixed and coniferous forests throughout the study area.
First chicks were seen on 23 June ( 1981). Maximum breeding den-
sity in 1981 was 1.0 territory/10 ha in each of two White Spruce-
Paper Birch Forest plots.
Ruffed Grouse. Bonasa umbellus. Rare visitant. One bird observed
20 May 1981 at the edge of an open white spruce forest at Kosina
Creek was the only record of the species in the study area. It is
a common resident in interior Alaska.
Willow Ptarmigan. Lagopus lagopus. Common resident and breeder in low
shrub thickets. Young were first .observed on 9 July (1981).
Maximum breeding density in 1981 was 0. 5 terri tory /10 ha in the
Dwarf-low Birch Shrub plot.
Rock Ptarmigan. Lagopus mutus. Common resident and breeder in dwarf
and low s.hrub and in bl ock;..fiel ds throughout the study area.
Chicks were first seen on 24 June (1981). Maximum breeding den-
sity in 1981 was 0.7 territory/10 ha in the Dwarf-Low Birch Shrub
plot.
White-tailed Ptarmigan. Lagopus leucurus. Uncommon resident and
breeder in dwarf shrub mat and block-fields. Species occurs at
higher elevations than its congeners, although at least several
hundred altitudinal feet of overlap was seen with Rock Ptarmigan.
No nests were found, but broods were seen at Mt. Watana beginning
on 10 August (1981).
Sandhill Crane. Grus canadensis. Uncommon migrant. Two flocks of cranes
were observed on 19 September 1980, Jne of 30 birds flying north-
east up Devil Creek and one of 105 birds flying northeast up
86
Tsusena Creek. Fifteen birds seen flying northwest over lower
Watana Creek by W. H. Busher on 15 May 1981 provided the only
additional record of the species.
Semi pal mated Plover> Charadrius semipalmatus. Uncommon breeder on
alluvial bars. Species occurred from 5 May (1981) to 8 September
{1980). Two nests with full clutches of four eggs were found, one
on 6 June and the other on 16 June 1981; both were along shorelines
of the Susitna River.
American Golden Plover. Pluvialis dominica. Common breeder in dwarf
shrub mat and·dwarf shrub meadows. Species occurred in the study
area from 15 May {1981) through 22 August (1980). Three nests
with four eggs each were found in 1981, the earliest on 12 June.
Maximum breeding density in 1981 was 1.5 territories/10 ha in the
Alpine Tundra plot.
Whimbrel. Numenius phaeopus. Uncommon probable breeder in dwarf shrub
meadow, occurring from 9 May (1981) to 6 August (1981) •
.
Upland Sandpiper. Bartramia longicauda. Rare probable breeder in dwarf
shrub meadow near scattered spruce woodlands. This shorebird was
observed only in 1980, when two birds were seen near Watana Camp
on 8 July, at least three birds were seen west of Kosina Creek on
13 July, and one was seen east of Kosina Creek on 19 July. It is
known to breed in the Alaska Range and along the Denali Highway
(Kessel and Gibson 1978).
Greater Yellowlegs. Tringa melanoleuca. Uncommon probable breeder in
wet meadows, foraging on fluviatile and lacus .... ·ine shorelines.
Species occurred from 29 April (1981) to 31 July {1980). Defen-
sive pairs were present near High Lake in mid-July 1980 and near
the White Spruce Scattered Woodland plot on 1 July 1981, but no
nests or young were found.
87
Lesser Yellowlegs. Tringa flavipes. Fairly common spring migrant; rare
summer visitant. In spring species occurred 6 May (1981) to
24 May (1981). Single birds were seen on 16 June 1981, 13 July
1980, and 23 July 1981.
Solitary Sandpiper. Tringa solitaria. Uncommon probable breeder in
scattered woodland or forest edge near lacustrine waters; rare
spring migrant. One migrant was seen 9 May 1981. At, least one
courting male was observed regularly about a beaver pond at
Sherman in June 1981.
Spotted Sandpiper •. Actitis macularia. Common breeder on alluvial
shorelines, especially along the larger creeks and rivers,
occurring from 19 May (1981) to 10 September (1980). Earliest
nest, with full clutch of four eggs, was found on a Susitna
riverbar on 6 June (1981). A brood of juvenal-plumaged young with
some down was seen on Kosina Creek on 17 July 1980, and an
independent juvenal was seen at Clarence Lake on 24 July 1981.
Wandering Tattler. Heteroscelus incanus. Uncommon possible breeder and
fal T migra,nt. The species was recorded 7-30 June 1981 and on
14 August and 8 September 1980. The June birds were in appro-
priate habitat for breeding, i.e., along tundra streams, but the
species is secretive and we noted no breeding behavior. Tattlers
breed in the Alaska Range (Kessel and Gibson 1978) and likely do
so in the study area·.
Turnstone. Arenaria sp.
were flushed from a
on 14 May 1981.
Rare migrant. Two unidentified turnstones
Susitna riverbar by an approaching helicopter
88
Northern Phalarope. Phalaropus lobatus. Fairly common probable
breeder, occurring in wet meadow pond areas from 9 May (1981) to
13 July 1981 and 12 July 1980. Maximum count was 24 birds seen
17 May 1981.
Common Snipe. Ga 11 i nago gall i nago. Common breeder in wet meadows,
where it occurred from 28 April {1981) to 31 July (1981). One
bird on 16 September 1981 was the only fall migrant recorded. A
clutch of four eggs found on 1 June 1981 hatched on 15 June.
Long-billed Dowitcher. Limnodromus scolopaceus. Uncommon spring
migrant. Two observations totaling three birds on 17 May 1981
constituted the only records.
Surfbird. Aphriza virgata. Rare possible breeder in dwarf shrub mat.
One bird seen 13 July 1980 west of Kosina Creek was the only
record, but the species is known to breed in the Alaska Range
{Kessel and Gibson 1978).
Sanderling. Calidris alba. Rare fall migrant. One juvenile at the
Tyone River mouth on 5 September 1980 was the only record.
Semipalmated Sandpiper. Calidris pusilla. Uncommon spring migrant,
recorded 6-20 May 1981, and rare summer visitant, recorded 25 and
30 June and on 23 July 1981.
Least Sandpiper. Calidris minutilla. Fairly common probable breeder in
wet and dwarf shrub meadows, occurring 9 May {1981) to 25 July
{1980). Aerial courtship displays were prominent May-July.
Baird•s Sandpiper. Calidris bairdii. Uncommon breeder in dwarf shrub
mat, occurring 15 May (1981) to 18 Ju1y (1980) •. A nest, with full
clutch of three eggs, was found 19 June 1981, and three downy
89
young were seen the same date. In 1981, the species was last seen
on the Alpine Tundra plot on 2 July, and on 7 July one individual
moved through and fed at lower elevations at the Dwarf-Low Birch
Shrub plot.
Pectoral Sandpiper. Calidris melanotos. Uncommon migrant in wet
meadows and at water edges. Three birds on 12 May 1981, six on
17 May 1981, and one on 16 September 1980 were the only records.
Long-tail~d Jaeger. Stercorarius longicaudus. Fairly common probable
breeder in dwarf shrub meadow and dwarf shrub mat. Earliest seen
in spring was 26 May (1981), latest 10 August (1981).
Herring Gull. Larus argentatus. Uncommon spring migrant and summer
visitant, occurring 3 May-14 June 1981; maximum was 15 birds seen
on 3 May 1981 during aerial survey.
Mew Gull. Larus canus. Common summer visitant and breeder about lacus-
trine and fluviatile waters; also flocked to refuse dump ·at High
Lake. Species occurred 30 April (1981) through 24 August (1980).
Large downy young were found at High Lake on 10 July 1980 and
6 July 1981; a brood of large, flightless chicks was on a pond
south of High Lake on 12 July 1980; and seven families of fledged
juvenal s were enumerated 27-29 July 1981.
Bonaparte•s Gull. Larus philadelphia. Uncommon summer visitant about
fluviatile and lacustrine waters, breeding in adjacent scattered
spruce woodlands. A fledged juvenal on WB 059 on 27 July 1981 was
the only evidence of breeding in the region.
Arctic Tern. Sterna paradisaea. Fairly common probable breeder about
lacustrine water shorelines. Species occurred from 6 May (1981)
to 16 August (1980). Maximum was seven scattered birds seen by
90
several field parties on 17 May 1981. No eggs or young were
found, but territorialism and aggressive behavior indicated
breeding.
Great Horned Owl. Babo virginianus. Uncommon resident and probable
br~eder in forests and woodlands. Heard calling in the upper
Basin 12 February 1981 and 6-7 March 1980. A probable family
group of three birds was present near Kosina Creek at least
between 20 May and 13 June 1981.
Snowy Owl. Nyctea scandiaca. Probably rare migrant. Two birds were
seen about 18 November 1981 by Craig Gardiner.
Hawk Owl. Surnia ulula. Uncommon resident and probable breeder in
mixed woodlands. Records of single birds were made from
22 February ( 1981) through early November ( 1981).
Short-eared Owl. Asia flamrneus. Uncommon migrant, summer visitant, and
possible breeder, occurring in all open habitats. Earliest in
spring were one on 27 April 1980 and one on 3 May 1981, and latest
in fall was on 21 October {1981).
Boreal Owl. Aegolius funereus. Rare resident and probable breeder
in mixed forests. Single observations, probably of the same bird,
on 18 April 1981 and 5 May 1981, were the only records.
Belted Kingfisher. Megaceryle alcyon. Uncommon probable breeder in
cutbanks. Species was recorded from 13 May (1981) through
11 September 1980 and 14 September 1981, primarily along the large
watercourses. A ~air was observed flying regularly between Kosina
Creek and a canyon across the Susitna River during July 1980,
apparently to a nest site in the canyon.
91
Common Flicker. Colaptes auratus. Uncommon breeder at forest edge.
This species was present as early as 6 May (1981) and as late as
11 September (1980). A pair was seen at a nest with young at
Kosina Creek on 20 June 1981.
Yellow-belli.ed Sapsucker. Sphyrapicus varius. No sapsuckers were seen,
but old sapwells on many of the large paper birches in the study
area attested their presence in earlier years. Most of the work-
ings were many years old, but some at the mouth of Kosina Creek
were relatively fresh, perhaps no older than about five years.
Similar old sapwells are numerous in the Tanana River Valley, and
in recent years a few sapsuckers have been seen in extreme eastern
interior Alaska (Kessel, pers. obs.).
Hairy Woodpecker. Picoides villosus. Uncommon resident and breeder in
mixed and deciduous forests. Most were seen in the vicinity of
Shennan or along Portage Creek. A female and ·fledged young were
seen together on the Cottonwood Forest plot at Sherman on 13 June
1981.
Downy Woodpecker. Picoides pubescens. Unc.ommon resident and probable
breeder in open mixed and deciduous forests. Single birds were
observed at irregular intervals during the 1980 study period, and
there was a portion of a breeding territory on the Cottonwood
Forest plot at Shennan during June 1981.
Black-backed Three-toed Woodpecker. Picoides arcticus. Probably rare
resident in coniferous forest. One male seen along Watana Creek
on 29 September 1980 was the only record.
Northern Three-toed Woodpecker. Picoides tridactylus. Uncommon resi-
dent and breeder in coniferous forests. A pair at a nest with
young was observed at Kosina Creek on 13 and 20 June 1981. The
nest was 8 m up in a 12-m black spruce.
92
Eastern Kingbird. Tyrannus tyrannus. Accidental. One bird observed
near High Lake on 11 July 1980 was the only record. In Alaska
this species is a regular visitant only in Southeastern; it is
casual elsewhere in the state (Kessel and Gibson 1978).
Say's Phoebe. Sayornis saya. Uncommon breeder on upland cliffs and in
buildings. A few birds were seen, mostly at Mt. Watana and in
mountains east of Watana Creek, from 28 May (1981) through 20 July
(1980). A pair was feeding young at a cliff on Mt. Watana on
13 July 1980, a bird was flushed from a nest in an old cabin on
Gilmore Creek on 29 June 1981, and a pair was present at V-Canyon
on 5 June 1981.
Alder Flycatcher. Empidonax alnorum. Uncommon probable breeder in
medium and tall shrub thickets. A late spring migrant, this
species was recorded first on 3 June (1981), when at least four
singing males were present in the vicinity of the Sherman camp-
site. Two juveniles at Stephan Lake on 21 August 1980 were fall
migrants, the latest individuals seen.
Western Wood Pewee. Con to pus sordidul us. Rare possible breeder in
deciduous forest. Four birds at Watana Creek on 25 July 1980
provided the only record.
Olive-sided Flycatcher. Nuttallornis borealis. Uncommon migrant and
probable breeder, 9ccurring in open forest and scattered woodland.
One singing bird at Watana Creek on 15 May 1981 was earliest seen,
and one bird at Stephan Lake on 23 August 1980 was latest.
Horned Lark. Eremophila al pestri s. Common migrant and fairly cr,nmon
breeder, occurring on passage in most open habitats and as a
breeder in block-fields and dwarf shrub mat. Three birds at
Watana Creek on 30 April 1981 were earliest in spring. Two nests
93
were found in 1981, both in high alpine dwarf shrub mat; one had
five eggs on 31 May, the other four eggs on 3 June. The first
fledgling was seen 20 June 1981. Postbreeding flocks were forming
16-21 August 1981, some shifting to lower elevations; four flocks
/
totaling 70 birds were seen at 1100 m in dwarf-low shrubs north-
west of Clarence Lake on 16 August 1981. Five birds on 23 September
1981 were latest fall migrants observed.
Vio.let-green Swallo.w. Tachycineta thalassina. Fairly common spring
migrant and summer visitant; probable breeder in riparian cliffs.
One bird on 16 May (1981) about ~'atana Camp was earliest in
spring, and none was seen after 25 July (1980), when two were
noted over Watana Creek.
Tree Swallow.
probable
waters.
Iridoprocne bicolor. Fairly common spring migrant and
breeder, occurring widely over lacustrine and fluviatile
.Two on 3 May ( 1981) over· ~~atana Creek were earliest in
spri.ng, and none was seen after 23 July ( 1980).
Bank Swallow. Riparia riparia. Uncommon local breeder and fall
migrant, occurring about riparian cutbanks and aver fluviatile
waters. There was a nesting colony of 25 pairs along upper Watana
Creek on 25 July 1980, the only evidence of breeding in the area.
The species was recorded no earlier than 4 June (1981) no-r later
than 21 August (1980).
Cliff Swallow. Petrochelidon pyrrhonota. Uncommon local summer visi-
tant and breeder, occurring about fluviatile and lacustrine
waters. The species was recorded only in the month of July (1980,
1981). Twenty birds in two colonies of five pairs each were seen
nesting under the eaves of two small cabins on the Watana Lake
shore on 9 July 1981, and a colony of seven pairs was seen at
Clarence Lake on 24 July 1981.
94
Gray Jay. Perisoreus canadensis. Common resident and breeder in coni-
ferous and mixed forests and woodlands throughout the study area.
Densities on four census plots in 1981 ranged from 0.5 to 1.0
fledged family/10 ha. One bird was observed in flight over low
shrub thickets" northwest of Cl a renee Lake on 5 September 1981, the
only occurrence noted far from timber.·
Black-billed Magpie. E.!£! pica. Uncommon visitant in spring, surrmer,
and fall; possible resident and breeder in open tall shrubs and
scattered woodlands.
Common Raven. Corvus corax. Common resident and breeder, nesting on
riparian and upland cliffs. Widespread, this species foraged in
or near most habitats and fed on game carcasses and about refuse
dumps in winter. Nests contained downy young at the time of the
aerial survey on 16-17 May 1981.
Black-capped Chickadee. Parus atricapillus. Uncommon resident and
probable breeder in deciduous forests~ Breeding territories were
found only on the Cottonwood Forest plat, where there were 1.8
territories/10 ha in 1981.
Boreal Chickadee. Parus hudsonicus. Fairly common resident and breeder
in coniferous and mixed forests. A pair was found feeding young
in a nest in the hollow top of a leaning 15 em dbh spruce snag on
the Black Spruce Dwarf Forest plat on 16 June 1981. Maximum
breeding density in 1981 was 1.7 territories/10 ha in.mixed white
spruce-paper birch forest.
Brown Creeper. Certhia familiaris. Uncommon breeder and fall visitant
in deciduous and mixed forests. A singing bird on 20 May {1981)
was earliest record, and one seen 21 October (1981) was latest in
fall. On 3 June 1981 a pair was seen entering a vertical cleft in
95
the bark 10m up the trunk of an 18-m cottonwood at Sherman. This
nest could not be examined, and no others were found. There were
two breeding territories in 1981 on the Cottonwood Forest plot and
one on the mixed White Spruce-Paper Birch Forest II plot.
Dipper. Cinclus mexicanus. Uncommon resident and probable breeder on
suitable fluviatile waters throughout the study area. We have no
observations from mid-winter, but between 17 and 23 Apri1 1981,
before spring thaw, birds were observed at open water sites along
creeks and rivers. Most were seen along the Susitna River at the
mouths of Watana, Deadman, and Tsusena creeks, and in Devil
Canyon.
American Robin. Turdus migratorius. Common spring migrant and breeder
and uncommon fall migrant, occurring from 25 Apri1 {1980) to
11 October {1981), although few were seen·after August. Species
occurred in forests and medium and tall shrub thickets. Two nests
with eggs were found, one in a paper birch near Shennan an 13 June
1981 and the other in high alpine tundra southeast of the Devil
Canyon dam site on 20 June 1981. The latter nest was on the
ground at the base of a 1-m high rock face. Maximum breeding
density in 1981 was 0.5 territory/10 ha on each of three census
plots: Tall A1der Shrub Thicket, White Spruce Scattered Woodland,
and Black Spruce Dwarf Forest.
Varied Thrush. Ixoreus naevius. Common spring migrant and breeder and
uncommon fall migrant, occurring in all forest types and in tall
alder shrub thtckets. Species was recorded in spring as early as
24 April (1981) and in fall as late as 20 September 1980 and
30 Septe111ber 1981. Four nests were found, the earliest, with four
eggs, on 21 May (1981). Nests were located in a spruce tree, an
alder shrub, and on an old stump. First nestlings were seen
13 June {1981), first fledglings on 20 June (1981). Most forest
96
plots supported breeding densities in 1981 of 2.5-3.5 territories/
10 ha, but there were 10 territories on the 10-ha Cottonwood
Forest plot.
Hermit Thrush. Catharus guttatus. Common breeder in forests on steep
slopes and in tall alder shrub thickets; uncommon fall migrant.
Species was first seen in spring on 14 May (1981), last in fall on.
7 September 1981 and 12 September 1980. Five nests were found in
1981, the earliest with a fulJ clutch of four. eggs on 25 May and
with nestlings with closed eyes but emerging primaries on 11 June.
A clumsy juvenal was seen in woods along Portage Creek on 31 July
1981. Maximum breeding density in 1981 was 6.1 territories/10 ha
in the Paper Birch Forest plot.
Swainson's Thrush. Catharus ustulatus. Fairly common breeder in all
forest types. Species occurred from 18 May (1981) to 27 August
(1980) •. A bird carrying nesting material in mixed forest on
20 May 1981, an adult carrying food in spruce forest on 17 July
1980, one feeding a fledgling on 15 July 1980, and many defensive
pairs observed at various times constituted breeding evidence.
Maximum breeding density in 1981 was 8.0 territories/10 ha on the
mixed White Spruce-Paper Birch Forest II plot.
Gray-cheeked Thrush. Catharus minimus. Fairly common breeder in scat-
tered woodland, in dwarf black spruce, and in the Cottonwood
Forest plot. Species occurred 20 May (1981) to 4 September
(1980). Earliest nest, on a 0.6 m high stump in the Cottonwood
Forest plot, had a full clutch of four eggs on 3 June 1981.
Maximum breeding densities in 1981 of 3.9 and 3.8 territories/
10 ha were on the White Spruc1; Scattered Woodland and the Cotton-
wood Forest plots, respectively.
97
Wheatear. Oenanthe oenanthe. Uncommon breeder in block-fields.
Earliest sighting was of one male west of Tsusena Creek on 31 May
(1981); none was seen after 30 August (1980), when one juvenile
was seen east of Devil Creek. No nests were found, but defensive
adults. were encountered in mid-July (1980, 1981), and bob-tailed
young were noted at the summit between Devil Creek and Watana Camp
on 18 July 1980.
Townsend's Solitaire. Myadestes townsendi. Uncommon spring migrant;
uncommon breeder on cliffs. One bird at Tsusena Butte on 17 May
1981 was our only record of a migrant. One was seen about a cliff
northeast of Jay Creek on 20 June 1981, and a pair at a nest with
young was observed at a rock outcrop in mountains northeast of
Watana Creek on 22 July 1980. Single birds seen 13 and 23 July
1980 were the only other records of the species.
Arctic Warbler. Phylloscopus borealis. Fairly common breeder in scat-
tered woodlands and medium shrub thickets as far east as the
slopes northwest of Clarence Lake; not detected on passage except
on 22 August 1980, when four birds were seen west of W?tana Camp.
Earliest record in spring was 11 June (1981). Twelve singing
males were counted on 11 July 1980 at High Lake, and food-carrying
adults were seen there on 1 August 1980. An adult feeding fledged
young was observed at WB 023 on 29 July 1981. Maximum breeding
density in 1981 was 4.8 territories/10 ha on the Medium Birch
Shrub Thicket census plot.
Golden-crowned Kinglet. Regulus satrapa. Uncommon spring and fall
visita.nt, occurring in coniferous and mixed forests. One bird
along the Susitna River on 24 April 1981 was the or•y spring
record; one bird was seen· at Cache Creek mouth on 9 September
1980; one was seen near the mouth of Tsusena Creek on 14 September
98
1980; two were seen on 12 September, four on 19th, and two on
25th--all in 1980 at Portage Creek; and two were observed at Gold
Creek on 4 October 1980.
Ruby-crowned Kinglet: Regulus calendula. Common migrant, and common
breeder in coniferous forests. Species was recorded in spring as
early as 3 May (1981), a singing male at Watana Creek, and in fall
as late as 25 September (1980). Four fledglings fed and begged
from their parents in the white spruce forest at Kosina Creek on
15-17 July 1980. Maximum breeding density in 1981 was 4.2 terri-
tories/10 ha in the White Spruce Forest plot.
Water Pipit. Anthus spinoletta. Common breeder about block-fields and
dwarf shrub mat, and common migrant, less cons.picuous in spring
than in fall. Earliest sighting in spring was of eight birds
along the Susitna River on 1 May (1981) and latest in fall was on
30 September (1981), except for a very 1 ate bird on 21 October
1981. Three nests were found on Mt. Watana in 1981, all in dwarf
shrub mat, the earliest with six eggs on 10 June. A nest on
19 June had three nestlings. Postbreeding flocking was first
noted in alpine areas on 10 August 1981, and small groups (two to
five birds) began to move to lower elevations at this same time.
Bohemian Waxing. Bombycilla garrulus. Common migrant and unco~non
probable breeder in scattered spruce woodland. A flock of about
25 birds at the mouth of Watana Creek on 21 March 1980 and a
single bird at the same place on 22 March 1981 were the earliest
seen; latest in fall was a flock of 12 birds along Watana Creek on
24 September. { 1980). Maximum number was 38 birds counted on a
5-km transect through scattered dwarf black spruce in the Fog
Lakes area on 9 May 1981. Late summer flocks included family
groups of recently fledged juvenals.
99
Northern Shrike. Lanius excubi tor. Uncommon breeder in ta 1l shrub
thickets and scattered spruce woodlands. Although probably
resident, species was first recorded on 25 April (1980); on
passage it occurred in all open vegetated habitats. A family
group of four birds, including at least two fledged young, was
seen near High Lake on 9 July 1980. One immature was observed
northwest of Clarence Lake on 16 September 1981, and an adult was
seen near Deadman Lake on 5 October 1981.
Orange-crowned Warbler. Vermivora celata. Uncommon breeder in medium
and tall shrub thickets and scattered woodlands. Earliest in
spring was a singing male at Sherman on 21 May (1981) and latest
in fall was one bird at High Lake on 7 September ( 1980). A nest
placed in moss under a dwarf shrub contained six eggs when first
found on 11 June 1981; the young hatched on 21 June.
Yellow Warbler. Dendroica petechia. Rare migrant and summer visitant.
A male sfnging at 04:20 on 15 June 1981 in riparian willows along
the Susitna River,.between Sherman and Devil Canyon, was not
present there hours 1 a ter or subsequently. One rna 1 e was observed
at Sherman on 30 July 1981, and three juveniles were seen there on
30 August 1980. There were no other records.
Yellow-rumped Warbler. Dendroica coronata. Common breeder in forests.
Earliest in spring was one on 8 May (1981) and latest in fall were
two on 24 September (1980). No nests were found, but food-
carrying adults were observed along the Susitna, below Watana
Creek, on 7 July 1980. Independent juvenals were recorded on
14 July·1980. Maximum breeding densities in 1981 were 9.8 terri-
tories/10 ha on the Paper Birch Forest plot and 9.5 territories/
10 ha on the mixed White Spruce-Paper Birch Forest II plot.
100
B1ackpol1 Warbler. Dendroica striata. Fairly common breeder in tall
shrub thickets, scattered woodlands, and in understory within
forests. Earliest in spring were two males on 18 May {1981). A
nest 1m up in a tall alder shrub of the understory of the Cotton-
wood Forest plot held six eggs when found on 13 June 1981; the
eggs hatched sometime between 14 and 19 June. Also, adults were
observed carrying food below Watana Camp on 7 July 1980. Maximum
breeding densities in 1981 were in the deciduous forests: 4.4
territories/10 ha in the Cottonwood Forest plot and 3.9 terri-
tories/10 ha in the P~per Birch Forest plot. A juvenile at Gold
Creek on 5 September 1980 was the latest record.
Northern Waterthrush. Seiurus noveboracensis. Fairly common probable
breeder in tall shrub thickets near water, often at deciduous and
mixed forest edges along the banks of the Susitna River. Earliest
in spring was a singing male on 15 May (1981), and latest in fall
was one bird on 6 September (1980). Maximum breeding density in
..
1981 was 6.1 territories/10 ha on the Cottonwood Forest plot.
wn son • s Warbler. Wil sonia pus ill a. Common breeder in medium shrub
thickets, with or without a forest overstory. Earliest in spring
was a male on 14 May (1981). A bird on 25 September (1981) was
latest in fall. A nest on the ground at the base of a willow in
scattered woodland contained six eggs on 14 June 1981 and five
young on 1 July. A defensive, food-carrying pair was observed on
7 July 1980. Maximum breeding densities in 1981 ranged from 8.8
to 9.4 territories/10 ha on the Low-medium Willow Shrub Thicket
and Medium Birch Shrub Thicket plots.
Rusty r1ackbird. Euphagus carol inus. Uncommon migrant and possible
rare breeder. Earliest in spring were sightings on 27 April 1980
and 2 May 1981; none was seen in spring after 24 May {1981). In
fall the species was recorded from 13 August (1980) through
101
25 September (1980). A bird seen on 29 July 1981 at WB 059 (Fog
Lakes) was the only midsummer record.
Pine Grosbeak. Pinicola enucleator. Uncommon spring, summer, and fall
visitant and possible breeder. A pair of birds on 16 May 1981,
two birds on 21 May 1981, three on 3 June 1981, one on 4 June
1981, one on 18 June 1981, three on 18 September 1980, and two
birds on 4 October 1980 were the only records.
Gray-crowned Rosy Finch. Leucosticte tephrocotis. Uncommon probable
breeder in cliffs and block-fields. A pair on 23 May (1981) \'las
earliest record; one bird on 23 September {1981) was latest.
Large postbreeding flocks {15-35 birds) were present on alpine
tundra from 10 August through 11 September 1981.
Common Redpoll. Carduel is flammea; Abundant and widely distributed at
all seasons; the most numerous passerine species recorded, but
bred in 1 ow densities. Four nests were found. Three pairs were
building nests 7-21 m up in 21-26 m cottonwoods on the Cottonwood
Forest plot on 21 and 22 May 1981. On 4 June 1981 a female incu-
bating four eggs was found 1.2 m up in a 1.5 m alder on a river
bar; the eggs hatched on 15 June. A flock of 200+ birds at High
Lake on 4 September 1980 was the largest flock seen.
Pine Siskin. Carduelis pinus. Irregularly uncommon summer visitant and
probable breeder; fairly·common in summer 1980 and distinctly
uncommon in summer 1981 (when the species was numerous from Kodiak
and Anchorage to Southeastern and when it bred as far north as
Fairbanks). Seen in mixed deciduous-coniferous forests and in
tall alder shrub thic~ets. Itinerant and irruptive and near the
northern limits of its range, this species probably breeds in the
study area in some years.
102
White-winged Crossbill. Loxia leucoptera. Fairly common summer visi-
tant and possible breeder in coniferous forests. Like those of
siskins and redpolls, numbers of this species fluctuate markedly
from year to year. Naximum counts were a flock of 65 crossbill s
that landed br~efly in cottonwoods near the Mixed II plot on
2 August 1981 and 36 birds seen at the Cottonwood Forest plot on
4 June 1981.
Savannah Sparrow. Passerculus sandwichensis. Abundant breeder through-
out the study area in open low shrub thickets with grass-sedge
ground cover. Earliest in spring was on 2 May (1981) and latest
in fall on 14 September ( 1981). Five nests were found, from
alpine tundra to scattered woodlands. Eggs were found in nests
from 7 June through 1 July 1981. First barely-fledged young was
recorded on 29 June (1981). Maximum breeding density in 1981 was
12.3 territories/10 ha on the Low-Medium Willow Shrub Thicket
plot. Postbreeding Savannah Sparrows did not fonn flocks. They
began gradually to disappear from the Dwarf-Low Birch Shrub plot
in mid-August 1981, and few were left by 25 August.
Dark-eyed Junco. Junco hyemalis. Common breeder, occurring throughout
forest and woodland habitats. It was recorded as early as 2 May
(1981) and as late as 29 September (1981), with an exceptionally
late bird on 30 October 1981. Maximum breeding densities in 1981
were 3.9-4.5 territories/10 ha in the White Spruce-Paper Birch
Forest plo~s.
Tree Sparrow. Spizella arborea. Abundant breeder in low shrub thickets.
Earliest record in spring was 6 May (1981) and latest records
in fall were 4 October 1980 and 6 October ·.381. First observation
of nesting was on 27 May (1981), when a pair was lining its nest
with ptannigan feathers. Nine nests were 1 ocated, with eggs
present from 7 June to 9 July. The first nestlings were found on
103
15 June (t981) and first fledglings on 28 June (1981). Maximum
breeding densities in t98t were t5.0 territories/tO ha on the
Low-Medium Willow Shrub plot and tt.8 territories/tO ha on the
Medium Birch Shrub plot. Tree Sparrows did not form postbreeding
flocks, but gr4dually left the Dwarf-Low Birch plot from 20 to
25 August t98t. Few birds remained on this plot after 2~ August
t981.
White-crowned Sparrow. Zonotrichia leucophrys. Abundant breeder,
widely distributed in low and medium shrub habitats. Species
occurred from 6 May (t98t) to 29 September (t98t). Eight nests
were found, the earliest, with four eggs, on 29 May (198t).
Nestlings were present in three nests on t5 June (t981), and some
had fledged by 29 June {1981). Average clutch size of five com-
pleted clutches in t98t was 4.8 eggs. Maximum breeding density in
t98t was 6.5 territories/tO ha on the White Spruce Scattered
Headland plot.
Golden-crowned Sparrow. Zonotrichia atricapilla. Uncommon probable
breeder in low shrub thickets and dwarf spruce forests. Species
was seen as early as t6 May (t98t) and as late as 3 September t98t
and 6 September t980.
Fox Sparrow. Passerella iliaca. Fairly common probable breeder in
medium and tall shrub thickets and in forest understory. Species
occurred from 8 May (t98t) through 7 September (t981). Maximum
breeding densities in t98t were 4.6 territories/10 ha on the
Cottonwood Forest plot and 3.5 territories/10 ha on the White
Spruce Scattered Woodland plot.
Lincoln•s Sparrow. Melospiza lincolnii. Uncommon probable breeder 1n
low and medium shrub thickets near water. Species occurred from
26 May (1981) through 7 September 1981 and 9 September 1980.
104
Lapland Longspur. Calcarius lapponicus. Abundant breeder in dwarf
shrub meadow and dwarf shrub mat. Species occurred from 24 April
(1981) through 16 September (1981), with an extremely l~te indivi-
dual seen 2 October 1981. Earliest nest, containing five eggs,
was seen 26 May (1981) and had four downy nestlings on 7 June
(1981). Longspurs began forming flocks on 25 July 1981 and. were
still moving through dwarf-low shrub habitat in large flocks
(15-70 birds) on 26 August 1981.
Smith's Longspur. Calcarius pictus. Uncommon probable breeder in dwarf
shrub meadow/mat. A pair north of Watana Camp on 8 July 1980, two
birds near Watana Lake on 13 July 1980, one male northwest of
Clarence Lake on 7 July 1981, and one male at the last location on
24 August 1981 were the only records of the species. The species
is known to breed along the Denali Highway (Kessel and Gibson
1978).
Snow Bunting. Plectrophenax nivalis. Fairly common probable breeder at
high elevations in cliffs and block-fields, feeding tn dwarf shrub
mat. Species was observed from 15 May (1981) to 19 October
(1981).
4 -NON-GAME (SMALL) MAMMALS -RESULTS AND DISCUSSION
4.1 -Species Composition and Relative Abundance
During the study peri·od we confirmed the presence of sixteen species of
small mammals in the upper Susitna River Basin (Table 22). In addition,
there was evidence of two other species in the region: a bat (two
separate sightings of what were probably little brown bats, Myotis
lucifugus, near High Lake and Tsusena Creek, August 1980, by J. Wilson
105
.TABLE 22
SPECIES OF SMALL MAMMALS FOUND IN THE UPPER SUSITNA RIVER BASIN, ALASKA,
1980 AND 1981
Order INSECTIVORA
Family Soricidae
Sorex cinereus, masked shrew
Sorex monticolus, dusky shrew
Sorex arcticus, arctic shrew
Sorex hoyi, pygmy shrew
Order LAGOf40RPHA
Family Ochotonidae
Ochotona collaris, collared pika
Family Leporidae
Lepus americanus, snowshoe hare
Order RODENTIA
Family Sciuridae
Mannota cal igata, hoary mannot
Spennophil us parryi i, arctic ground squirrel
Tamiasciurus hudsonicus, red squirrel
Family Cricetidae
Clethrionomys rutilus, northern red-backed vole
Microtus pennsylvanicus, meadow vole
Microtus oeconomus, tundra vole
Microtus miurus, singing vole
Lemrnus sibiricus, brown lemming
Synaptornys borealis, northern bog lemming
Family Erethizontidae
Erethizon dorsatum, porcupine
106
and s. W. Buskirk); and water shrew, Sorex palustris (tracks of a small
mammal between ice openings on Watana Creek, March 1980, by S. w.
Buskirk).
Comparison of our species list with the literature and several
unpublished sources shows few distributional surprises. Our discovery
of arctic shrews in the study area constitutes a minor range extension;
the closest previous record was from Denali National Park (Murie 1962).
To inventory the shrews and voles of the upper Susitna Basin, we con-
ducted one spring and two fall trapline surveys, involving a total of
16,776 trap nights of effort. This effort resulted in the capture of
1752 microtine rodents (6 species) and 1747 shrews (4 species). The two
most abundant animals, constituting 76% of total captures, were northern
· red-backed voles, represented by 1382 specimens, and masked shrews,
represented by 1286 specimens. Other shrews captured were arctic shrews
(297 specimens), dusky shrews (153), and pygmy shrews (11). Microtus
specimens inclu.ded 203 tundra voles, 68 meadow voles, and 75 singing
voles. Small numbers of brown lemmings (20) and northern bog lemmings
(4) were also taken.
Capture results from sites sampled during all three trapping periods
indicated a pronounced temporal difference in small mammal abundance
(Fig. 6). Trapping in fall 1980 resulted in 941 animal captures, com-
pared to 125 the following May and 1231 in fall 1981. Comparison of
fall numbers shows that tundra voles were twice as abundant in 1981 as
in 1980, red-backed voles 1.7 times more abundant, and masked shrews 1.3
times more abundant. Fall capture numbers of meadow voles, arctic
shrews, and pygmy shrews were about equal, while dusky shrews declined
sharply. We capturP~ brown lemmings (6 specimens) and bog lemmings (3)
in 1981 only. Regardless of the temporal differences in population
107
en
UJ c::
~
600
500.
400
1-300
0. c:c
(.)
u.
0
c::
UJ 200 IX]
~
~ z
9
I
I
I
I
I
I
I
I
I MS I
0 :
\ I
\ I
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\ I
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\ ' \ I
\ I
\ '
\ ' \ ' \ I
\ '
\ ' \ . ' \ :
\ '
\ ' \ I
\ '
\ ' \ I
100 \ ' o~··. \ [(: • •. \ I
•. \ I
••• \ I \I ...... 0
PS -..... • ... ••0 ·------! .!.::... -·
FIGURE 6
0 co
Ql -
SHREWS
600
500
400
300
200
100
0
' ' ' ' ' I
' I
I
I
I
I
I
I
I
I
I
I
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' ' ' ' ' R-bV :
0 ' \ I
\ I
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\ I
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0
VOLES
Temporal variation in numbers of small mammal captures at 22 trapline
sites in the upper Susitna River Basi~, Alaska, 1980-81 (MS = masked
shrew, AS = arctic shrew, DS = dusky shrew, PS = pygmy shrew, R-bV =
northern red-backed vole, TV= tundra vole, MV =meadow vole).
108
levels, the relative abundance ranking among species remained the same,
i.e., the common species remained common and the rare continued to be
rare.
Six small mammal spe<:ies not sampled on our traplines also occurred in
the study area: arctic ground squirrel, hoary marmot, collared pika,
red squirrel, porcupine, and snowshoe hare.
The arctic ground squirrel was a numerous and ecologically important
mammal of the region. Although the largest numbers were found on the
drier slopes, knolls, and ridges above treeline, small numbers occurred
at lower elevations: one near the mouth of Tsusena Creek, several along
the railroad sidings at Sherman and Curry, and one 0.8 km below treeline
in mixed forest near Portage Creek.
During the snow-free months ground squirrels provide an abundant, reli-
able food source for a number of mammal ian and avian predator's (Carl
1962, Murie 1962, Bente 1981, Olendorff 1976). At High Lake in 1981 the
first ground squirrel emerged from hibernation the third week of April;
the last squirrel seen here in fall was 4 October 1981 (E. Powell, pers.
comm.). These emergence and entrance dates are essentially the same as
those reported by Hack (1960) and Hock and Cottini (1966) in the
Talkeetna Mountains near Anchorage, and by Carl (1962) at Ogotoruk
Creek, northwestern Alaska. Seasonal chronologies (after Hock 1960) in
ground squirrels in the Talkeetna Mountains, approximately 120 km south
~f.the study area, are shown in Figure 7.
General observations indicated that the Susitna study area supports a
relatively high and stable population of ground squirrels, probably
comparable to densities reported elsewhere in the State. For example,
in the Talkeetna Mountains to the south, Hock and Cottini (1966), on
20 June 1951, removed 27 squirrels from an area about 100 m x 50 m with
little apparent decrease in numbers; the squirrel population in this
109
HIBERNATION
JA ' FE MR
FIGURE 7
FATTENING ALL FATTENING
LACTATION ...
YG EMERGE ... ,.
BREEDING BIRTH
CARE OF VOUNG
GESTATION
AP MY JN JL AU
-ENTER HIBERNACULA
HIBERNATION
SE OC -.-NO DE
Seasonal chronologies of the arctic ground squirrel, Talkeetna
Mountains near Anchorage, Alaska (after Hock and Cottini 1966).
1.10
area remained high throughout four years of study. In the eastern
Brooks Range, Bee and Hall (1956) counted 175 ground squirrels along a
1-km ridge, and, in another location nearby, 70 squirrels on approxi-
mately 1.5 ha of hillside. At Ogotoruk Creek, near the extreme western
end of the Brooks Rapge, Carl (1962, 1971) estimated a'maximum number of
. 220 animals on his 29-ha (72-acre) study plot during the month of July
1961.
Hoary marmots were locally common residents of the alpine zone. We
found scattered colonies above treeline above 1000 m. None was seen
within proposed impoundment areas. Marmots hibernate longer than ground
squirrels; in the Talkeetna Mountains near Anchorage, marmots emerge
from hibernation during the first third of May and begin entering
hibernacula in early September (Hock and Cottini 1966).
Hock and Cottini {1966) suggested that a portion of their marmot popula-
tion underwent seasonal shifts in altitude, moving down from high rocky
slopes in fall ·to sites having better soil conditions for winter denning
and having an available food supply in early spring. An opposite
seasonal movement apparently occurs in some Montana hoary marmot
colonies (Barash 1974). The only suggestion of fall movement in the
upper Susitna River Basin was the observation of several marmot trails
and a single marmot traversing the 1067 m-high valley near Swimming Bear
Lake (WB 150) in about 8 em of snow on 10 October 1980 (T. W. Hobgood,
pers. comm.).
Another locally common alpine species was the collared pika. It
occurred regularly in talus slopes at higher elevations. As in the case
of marmots, no pikas were seen below treeline. -
Densities of pikas varied from five animals/ha in large rock slides, to
25/ha on small, isolated rock piles at Denali National Park in 1962
(Broadbooks 1965).
111
Active throughout the year (Sheldon 1930, Broadbooks 1965, Hock and
Cottini 1966), pikas store large quantities of dried plant material in
late summer for use during the winter months.
Evidence of avian pr~dation on this species was our discovery of pika
bones in a raptor upellet" (bird species unknown) near the edge of montane
alder thickets in fall 1981. Observations in other areas suggest that the
short-tailed weasel (Mustela enninea) is an important mammalian predator of
the pika {S. 0. MacDonald pers. obs., Rausch 1961, Broadbooks 1965).
In contrast to the three alpine species, red squirrels, porcupines, and
snowshoe hares were generally confined to the forested areas of the
Basin. Within these areas red squirrels were fairly common, while
porcupines and snowshoe ~ares were unconunon. Snowshoe hares, a major
source of food for predators over much ·of central Alaska, were generally
restricted to areas east of Watana Creek. Localized "pockets 11 occurred
primarily in the vicinities of Jay Creek, Goose Creek, and the lower
Oshetna River.·· Long-tenn information on overall hare abundance, pro-
vided by several local residents, indicated that the low number of hares
during our study is a chronic situation and not just a low stage of a
population cycle.
4.2-Small Mammal/Habitat Relationships
{a) Shrews and Voles
Forty-two trapping sites were organized into floristically similar groups
by using a cluster analysis of frequency counts of 81 plant taxa in the
ground cover (Fig. 8). The major groups that emerged from this analysis
corresponded to the following vegetation types of Viereck and Dyrness 1980:
1) herbacecus and dwarf and low shrub, 2) conifer-ous forest and woodland,
and 3) mixed forest, deciduous forest, tall shrub, and tall grass. Within
major groups, clustered subgroups roughly corresponded to sedge-grass
112
* >-
1-
tr
<
.J
:E -en
w
>
1-<
.J
11.1 a:
MIXED &
HEIRBACEOUS-DECIDUOUS
t:::=D=W=A=R=F=a=L=a=w=s=H=R=U=B==:J. cc=o=N=I=F=E=R=o==u=s==F=O=R:::::·::E=S::rT T A E P ~EHSRTU 8
I
I •
:sEoGE-c:;RASS/:
ISHRUB TUNDRA:
I •
TRAPLINE 2 8 7 2 2 1 6
SITE NO. 4 0 9
·~
""'""
""'I"'
so-
FIGURE 8
liD.
::I •
Ia: •
SEDGE-GRASS/ LOW ~OPEN -.WOODLAND
1a:cr. SPRUCE-SPRUCE
WILLOW SHRUB ~~
I
I . o Q BOG 1 BIRCH-.a..COTTON-.a.. TALL ""-TALL1
1 SPRUCE¥ WOOD ¥ALOER¥GRASS1
21112211514443222244493343334443311
58103267 445676798789 3409651231232
I
.... ,... I'"'
~I'"' ...... .......
~ ... I""" ._
~...,..
I
I
Clustering of 42 small mammal trapl~ne sites into similar vegetative groupings,
based on an analysis of frequency counts of 81 plant taxa in the ground cover.
113
and shrub tundra, sedge-grass and low willow shrub; herbaceous-mixed low
shrub meadow, open white spruce forest to black spruce bog (low birch
shrub sites also clustered with this group); and paper birch-white
spruce forest, cottonwood forest, tall alder shrub, and tall grass
meadow (the 1 ast wi tp a tall shrub component). The number of captures
of each small mammal species relative to these vegetation types is shown
in Figure 9.
Trapline site ordination by principal component analyses (PCA) provided
essentially the same general groupings as the clustering technique,
despite use of structural habitat variables instead of plant taxa counts.
This approach also tends to emphasize habitat continuity. The resultant
ordinations of 43 trapline sites trapped in fall 1981 are shown in
Figure 10, and those of 22 sites trapped during all three sampling
periods are shown in Figure 12 (p. 124).
By using the relative abundance of a given small mammal species at each
trapping site as a vertical axis on the PCA ordinations (see Section
2.8), a general habitat occupancy pattern becomes visible (Fig. 11).
Shrews and red-backed voles in the upper Susitna River Basin displayed-a
relatively broad and uniform distribution pattern across the habitat
landscape. Masked shrews, the numerically dominant shrew species,
occurred at all trapping sites. They were most numerous in deciduous
forest (particularly cottonwood), grassland, and tall shrub sites.
Arctic shrews occurred at 29 trapl ine sites, with peaks of abundance on
the drier non-forested sites, particularily grassland (at low eleva-
tions) and low shrub (above treeline). Dusky shrews were thinly distri-
buted across the vegetation types of the study area. Although we captured
them at 23 sites, no particular preferences were apparent; however, they
may have avoided the wettest sites. The few captures rf pygmy shrew in
cottonwood forest (3 specimens), white spruce forest \1), and grassland
(1) during the fall 1981 trapping, and open spruce forests (5) and
cottonwood forest (1) during fall 1980, suggest a possible restriction
of this species to forest.
114
--' ..,...
01
to ,. MEADOW VOLE .. •• .. ::10 "' so :::1 .. .. e so .. • • c .. u .... ... 30 u " .. 30 0 20 0 " 0 ao •• " • 10 • • • • •• 0
70
JO TUNDRA VOLE .. 110 .. so 0: .. .. •• .. .. u :10 ... • • " 0 20
• • ••
• • 0 • • • • •
SINGING VOLE ...
•
JO BROWN LEMMING 70
:: 60
0: "so
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u
... 30
0
0 2o .. •• • • 0
: HEA84CI01(1• : CONIFIROV• : IIIUO A :
: OW.UF a LOW <8HRV8: FOREST : OEC~~~~U:H:::·-:
~~D<oi::oia-ui:iEDG,:-Gi.iii'iiO]wYiirtN-.; ;;;.; .. ;-.; -.oa-ti,;~: ~co;,~~ .. L :!~L~-!
1MAOI ~A 1 WILLO• StlfiUI JJ SPfluce IPIIUCI :IPIIIUCI WQOD ~"lORAU:
t I I 4 I
I I I 1 . . . .__ ------------·------------1-~------___ ....
F.iC'IRE 9
MASKED SHREW •
• • •
• • • • •• • • • • • • •••••• • ·~ • • • •• • • • •• • •• • •
ARCTIC SHREW
• •
• • • • • •
DUSKY SHREW
NORTHERN RED-BACKED VOLE
•
• • • • • • • • • •
•
• • ••• •
•
• ••
•
• •
•• •
• •• •
• •••
Abundance of eight small mammal species relative .to vegetation types at 42 trapline sites in
the upper Susitna River Basin, Alaska, 29 July-30 August 1981.
FIGURE 10
Two-dimensional ordination of 43 small mammal trapline sites trapped
in fall 1981, upper Susitna River Basin, Alaska, based on principal
component analyses of ground-1 eve1 structur.al habitat variables. The
two principal components accounted for 41% of total variance in
measured variables among sites. Vegetation types that correspond to
the groupings of mean factor score centroids are indicated~
116
GROUPINGS OF 43 TRAPLINE SITES ALL SPEC.IES
MASKED SHREW ARCTIC SHREW
DUSKY SHREW NORTHERN RED-BACKED VOLE
FIGURE 11
Habitat occupancy patterns of small mammals captured at 43 trapline sites,
upper Susitna River Basin, Alaska, 29 July-30 August 1981. Species relative
abundance has been added as a vertical axis to the two-dimensional PCA
ordination shown in Figure 10 (see Methods, Section 2.8).
H7
MEADOW VOLE TUNDRA VOLE
SINGING VOLE BROWN LEMMING
FIGURE 11 (Continued)
118
Red-backed voles, the dominant microtine of the region, occurred on all
but five trapping sites. Although red-backed vole abundance levels were
roughly similar across most forest and shrub types, greatest numbers
6Ccurred in open and woodland spruce and cottonwood forest sites.
"" Herbaceous meadows, ~articularly in wet situations, harbored lower
red-backed vole densities, as did paper birch forest.
In contrast to the more general habitat occupancy patterns of most
shrews and of red-backed voles, the three Microtus species displayed
stronger habitat specificity, as evidenced by their general restriction
to open, non-forested sites (Fig. 11}. Singing vole colonies were found
in open low shrub, herbaceous tundra, and mat and cushion tundra above
treeline. Captured on only 10 trapline transects, they were most abundant
in open low willow-birch shrub on relatively dry soils. Tundra voles
and meadow voles occurred primarily in sedge and grass-forb meadows and
bogs. We captured tundra voles on 22 sites (primarily grass-forb, but
also sedge-grass), compared to 10 for meadow voles (primarily wet sedge-
grass). Sman·numbers of brown lemmings were captured on 11 sites at or
above treeline, usually in wet herbaceous and low shrub situations. Bog
lemmings were taken at lower elevations in mesic sedge-grass/low shrub
meadow (2 captures), grass meadow (1), and near a seepage in white
spruce forest (1).
Some of the small mammal species occupied a broad range of vegetation
types, while others were more restricted. We quantified these differ-
ences by calculating a standardized habitat niche breadth measure for
each species captured during fall 1981 (Table 23). The ubiquitous
masked shrew and red-backed vole had the broadest habitat niche breadth,
followed closely by dusky shrew and arctic shrew. Microtus species, and
particularly singing voles, had the narrowest habitat niche breadths,
along with the rare or uncommon pygmy shrew, bog lemming, and brown
lemming.
119
TABLE 23
STANDARDIZED HABITAT NICHE BREADTH VALUES FOR TEN SMALL MAMMAL SPECIES
SAMPLED BY SNAP AND PITFALL TRAPPING AT 43 SITES, UPPER SUSITNA RIVER
ffASIN, FALL 1981. (SEE SECTION 2.8 FOR CALCULATION OF Ed. AND HABITAT ~ICHE BREADTH VALUES.) 1
"
Standardized
Species (Sum of captures/100 TN [Ed;]) habitat niche breadth value
Masked shrew (464.7) 0.60
Northern red-backed vole (454.8) 0.59
·Dusky shrew (28.3) 0.45
Arctic shrew (96.3) 0.38
Brown lemming (10.2) 0.21
Tundra vol1e (87.7) 0.17
Northern bog lemming (2.2) 0.09
Meadow vole (43.8) 0.08
Pygmy shrew (2.8) 0.08
Singing vole (42.7) 0.05
120
As population densities fluctuate over time, a species might be expected
to expand its range into suboptimal habitat during periods of high
density and contract its-range to optimal habitat during periods of low
Jensity (Guthrie 1968, others). Changes in habitat niche breadth for
species captured in the upper Susitna River Basin generally reflect such
changes (Table 24). Variation in habitat niche breadth between periods
seems to parallel changes in abundance for masked shrews, red-backed
voles, and dusky shrews. In masked shrews and red-backed voles, niche
breadth varied little, despite large variations in abundance. Range
contraction did not occur in arctic shrews, however, which increased in
niche breadth despite a slight decline in abundance. The habitat niche
breadth of the tundra vole remained essentially constant, despite a
two-fold population increase from fall 1980 to fall 1981. The opposite
occurred with the meadow vole, in which abundance levels were constant
from fa11 to fall, yet niche breadth increased.
Interspec·i fie interactions, particularly among ecologically similar
species, can play a major role in determining intraspecific habitat
utilization (MacArthur and Wilson 1967} and may help explain the
apparent anomalies we witnessed in shifts of habitat niche breadth
values. To avoid competing for limited resources, species may occupy
different habitats, or may occupy the same habitat but exploit its
resources (food, den sites, etc.) in different ways and/or at different
times. Closely related species, similar in size and broadly overlapping
in food requirements, should display the greatest degree of habitat
segregation (Grant 1978). Discrete habitat distribution patterns among
the Basin's three Microtus species (Fig. 11) supports this conjecture:
Singing voles and meadow voles occupied a narrow and non-overlapping
range of habitats, suggestive of species having strong and different
habitat preferences. Tundra voles, in contrast, displayed a more
diffuse and overlapping pattern of habitat occupancy, suggestive of a
more ecologically flexible species, although their peak densities
occurred on sites essentially devoid of either congener.
121
TABLE 24
STANDARDIZED HABITAT NICHE BREADTH VALUES FOR SIX SMALL MAMMAL SPECIES
CAPTURED ON 22 TRAPPING SITES, DURING THREE SAMPLING PERIODS, UPPER
SOSITNA RIVER BASIN, 1980-81. (SEE SECTION 2.8 FOR CALCULATION OF
HABITAT NICHE BREADTH VALUES.)
Standardized habitat niche breadth
values {Samele size}
Species Fall 1980 Spring 1981 Fall 1981
Masked shrew 0.71(361) 0.34(39) 0.76(478}
Dusky shrew 0.65(96) 0.00(0) 0.47(26)
Arctic shrew 0.31(118) 0.04(3} 0.44(101)
Northern red-backed vole 0.68(333) 0.57(94) 0.78(616}
Meadow vole 0.05(13) 0.00(0) 0.13(13)
Tundra vole 0.16(24} 0.04(1) 0.17(57)
122
A comparison of the habitat occupancy patterns of the tundra and meadow
voles between fall 1980 and fall 1981 (Fig. 13) shows that while the
tundra vole population increased substantially the second year, spill-
over into other meadow habitats was not evident (breadth values remained
>
constant). Also, while meadow vole abundance was similar between years,
habitat shift and expansion occurred the second year (breadth values
increased)--but into habitats not occupied by its congener. Habitat
segregation between two similar species was thus maintained and the
possibility for overt competitive interactions reduced.
There was no clear pattern of habitat segregation between red-backed
voles and Microtus species. Capture information on sites with low
numbers of Microtus in fall 1980 and high numbers the following year
showed an inverse relationship in red-backed vole numbers (in spite of
the fact that this vole was also more abundant the second year). West
~1979), noting a similar situation for red-backed voles and Microtus in
the Yukon-Tanana Highlands, attributed it to competitive exclusion.
Other studies (Morris 1969, Turner et al. 1975) also have shown that
Microtus and red-backed voles tend to exclude each other from certain
·sites.
Among members of the Susitna River Basin•s diverse microtine fauna,
then, red-backed voles were the most abundant and widespread. A habitat
generalist, the species dominated the forest and shrublands of the area.
Open herbaceous-dominant habitats, left vacant by declining Microtus
populations, were quickly colonized and dominated by this adaptable
vole, which has a relatively unspecialized tooth structure (Guthrie
1965) and generalized feeding habits (Guthrie 1965, Grodzinski 1971,
Bangs 1979, West 1979). Although red-backed vole numbers can vary
considerably from year to year, the magnitude uf change is usually less
dramatic (and also less predictable) than that of such open country
species as Microtus and Lemmus (Pitel ka 1967, Whitney 1976, West 1979).
123
FIGURE 12
...
0
~
! .... , ,..
I"'
0
~
Two-dimensional ordination of 22 small mammal trapline sites trapped
during all three 1980-81 sampling periods, upper Susitna River Basin,
Alaska, based on principal component analyses of ground-level structural
habitat variables. The two principal.components accounted for 40% of
total variance in measured variables among sites. Vegetation types that
correspond to the groupings of mean factor score centroids are indicated.
124
..
_.-GROUPINGS OF 22 TRAPLINE SITES
FALL 1980 FALL 1981.
TUNDRA VOLE
FALL 1980 FALL 1981
MEADOW VOLE
FIGURE 13
Changes in habitat occupancy patterns of tundra voles and meadow voles
between fall 1980 and fall 1981, upper Susitna River Basin, Alaska. Species
relative abundance has been added as a vertical axis to the two-dimensional
PCA ordination shown in Figure 12 (see Methods, Section 2.8).
125
Members of the genus Microtus were restricted to, and specialized in,
meadow and meadow/shrub habitats found scattered about the Basin•s
landscape. All have more specialized tooth morphologies and diets than
ll_ave red-backed voles (Guthrie 1965, West 1979). The similarity of
/habitat and trophic requirements among Microtus is most pronounced in
tundra voles and meadow voles (\~est 1979}, and the impact of competition
probably plays a major role in detennining the dynamic spatial relation-
ships between the two. Among Microtus, tundra voles appear the most
ecologically flexible, in that they have a somewhat simpler tooth struc-
ture (Guthrie 1965), broader food habits (West 1979}, and wider toler-
ance to di·ffering vegetation types (West 1979, this study) than have
their congeners. As suggested by West {1979), such flexib·ility probably
accounts for the fact that among the three Microtus species occurring in
the Susitna Basin, tundra voles seemed better able to find and exploit
isolated 11 pockets 11 and. border patches of suitable habitat. This flexi-
bility might also explain why tundra voles were the only Microtus found
on the two Susitna River islands sampled during 1981.
Northern bog lemmings and brown lemmings did not appear to be major
microtine constituents in the study area. Bog lemmings are generally
uncommon throughout· their range, and little is krown of their ecological
requirements (Banfield 1974, West 1979, MacDonald 1980). In other areas
of the State, small numbers have been taken primarily in shrub bogs and
marshes (Osgood 1900, Dice 1921, West 1979, MacDonald 1980)--not unlike
the few sites where we found them during this study. Their diet is
apparently restricted to sedges, grasses, some forbs (Cowan and Guiguet
1956) and mosses (West 1979).
Although the high country of the upper Susitna Basin has an apparent
abundance of suitable brown lemming habitat, we captured only small,
scattered numbers during our study. They have been found in fairly
large numbers in other montane ar.eas of central Alaska (R. L. Rausch
pers. comm.), so perhaps we failed to sample the right habitat, or, more
1.26
likely, sampled during a period of low population levels. Brown
lenvnings are usually assoC'iated with wet sedge-grass tundra above tree-
line, but are also found locally at lower elevations in spruce bogs and
;et meadows (Buckley and Libby 1957, Banfield 1974). This species is
almost completely dependent on a diet of sedges and grasses (Guthrie
1968), although mosses may be important at times (West 1979).
Among the insectivorous shrews, habitat occupancy patterns indicated
considerable spatial overlap between species and only weak habitat
preferences. Hence, competition could help explain the apparent inverse
relationship of masked shrew abundance and the abundance of the other
shrew species, particularly the similarly-sized dusky shrews and pygmy
shrews. Confounding factors, not obvious from our data, could also be
involved (Terry 1981): (1) Shrews coexist in the same habitats, and·
their environmental requisites are less simi1ar than assumed (Disparity
in body size between masked shrews and arctic shrews suggests the ability
to coexist [see Brown 1975], which might explain why arctic shrew
abundance appeared least affected by masked shrew abundance in fall
1981); (2) they occupy distinct subdivisions of the habitats (i.e.,
microhabitats); or (3) habitat coexistence (macro-and micro-) is
occurring because critical resources are not limited.
(b) Other Species
Arctic ground squirrels inhabit herbaceous tundra and open shrub
habitats above treeline (Guthrie 1967, Kurten and Anderson 1980, this -.· . :•
study). At lower elevations they also colonize riverbanks, lakeshores,
moraines, eskers, road sidings, and other disturbed sites with subclimax
vegetation (Banfield 1974, Guthrie 1968, this study). Our observations
corroborate Bee :md Hall's (1956) conclusion for the Brooks Range that
the optimum conditions for ground squirrel colonies are (1) loose
penna frost-free soils on well-drained slopes, (2) vantage points from
which the surrounding terrain can be observed, and (3) bare soils
127
surrounded by vegetation that is in an early xerosere stage of succes-
sion. Carl (1962) found ground squirrels avoided sites where tall
vegetation (greater than 20 em) impaired vision. The effects of
_squirrel activity--e.g., burrowing, mound building, feeding, feces
/
deposition--within areas of established colonies tends to maintain
vegetation at an early successional stage (Carl 1962, Youngman 1975).
Hoary marmots and collared pikas are generally restricted to tundra/
block-field habitats at high elevations (Hoffmann et al. 1979, this
study). Both are ecotone species: their homes and shelters are in one
habitat (rocks of various particle size and shape) and their food in
another (various herbaceous tundra ~ypes) (Broadbooks 1965). The co-
occurrence of marmots, pikas, and even ground squirrels in apparently
the same habitat suggests high potential for both competitive and
cooperative interactions.
The arboreal red squirrel occupies a variety of forest habitats, but
prefers mature ·coniferous forest (Cowan and Guiguet 1956). White spruce
forest is generally considered the optimal habitat in interior Alaska
(Nodl er 1973, others). Here, red squirrels feed primarily on the seeds
of spruce, particularly white spruce, but supplement their diet with
fungi, fruits, and even the buds of spruce and aspen (Smith 1967, Nadler
1973). They store large quantities of spruce cones, and mushrooms when
available, in "middens 11 for winter use (f~urie 1927, Streubel 1968).
Buskirk (pers. comm.) noted that, in fall 1981, red squirrel middens in
his study area appeared composed only of mushrooms and spruce buds. A
massive cone crop failure caused by an area~wide epidemic of white
spruce needle rust (Chrysomyxa ledicola) during 1980 (J. H. McBeath,
Univ. Alaska Agric. Expt. Station, pers. comm.) would explain why
squirrels were storing such 1 ow qual Hy food as spruce buds (Smith
1967). What long-term effects this crop failure might have on the upper
Susitna River Basin's red squirrel population is not known, but Smith
(1967) reported a 67% drop in a red squirrel population following the
128
second year of a two-year cone crop failure in white spruce forest and
suggested that the squirrels had emigrated into surrounding black spruce
stands.
Porcupines occupy a broad range of forest and shrub habitats (Woods
1973). In mountainous regions they prefer heavily wooded forests during .
the winter (Hock and Cottini 1966, Harder 1979), but may occasionally be
found above treeline, even during the coldest months (Irving and Krog
1955). We recorded occasional porcupines only in forested areas of the
upper Susitna River Basin.
In interior Alaska, Wolff (1977) found that snowshoe hare habitat
preference depended on population density: during population lows hares
were restricted to dense black spruce forest and willow-alder thickets;
during highs they used a wider variety of vegetation types, including
recently burned areas with minimal cover. He concluded that a patchy
environment of recently burned sites with inclusions of unburned spruce
was the preferred hare habitat. The chronic scarcity of snowshoe hares
in the upper Susitna River ·Basin was probably related to a scarcity of
suitable habitat. Noticeably absent from this area were recent burns
and riparian shrub thickets--early successional habitats that could
provide hares the opportunity to substantially increase and expand their
numbers beyond the safe but unproductive stands of dense spruce and
alder thickets in which we found them.
129
5 -ANTICIPATED IMPACTS
5.1 -Watana Dam and Impoundment
(a) Impoundmen.t
The general types of _impacts on raptors that can result from development.
activities are listed in Tables 17-19; inundation is an additional
impact of hydroelectric projects. The Watana impoundment would flood
15.1 km of the better quality raptor cliffs (type 11 A11
}, leaving only
0.9 km above waterline (Table 20). Four active and four inactive Golden
Eagle nest sites, two active and one inactive Bald Eagle sites, and two
inactive raven sites would be destroyed (Table 21). Loss of this
nesting habitat would force these birds to other sites, either along the
remaining. cliffs of the Susitna River and tributaries or in the nearby
cliff-tor habitat of the uplands, or, in the case of Bald Eagles, to
other nest trees. Unflooded cliff habitat in the surrounding area
(e.g., along Fog and Tsusena creeks and those draining into the south
side of the Devil Canyon impoundment) could increase in importance to
these_ birds. If fish became avail able in the impoundment (which now
appears unlikely}, Bald Eagles might use large trees surrounding the
impoundment for nesting.
The impoundment would destroy the breeding habitat of about 33,000 pairs
of small-and medium-sized upland birds (Table 25). More than 1000
breeding territories of each of 13 bird species would be flooded
(Table 25):. with the following species each losing over 2000 breeding
territories: Yellow-rumped Warbler (3900), Ruby-crowned Kinglet (3600},
Dark-eyed Junco (3000), Swainson's Thrush (2900}, Tree Sp~rrow (2800),
Varied Thrush (2000), and Wilson's Warbler {2000). Approximately 65 km 2
of forest habitats would be inundated, habitats that generally support
the highest bird de·nsities of the region (Table 8). A number of bird
species are restricted to forest habitats for breeding (see Table 9}, as
130
TABLE 25
. ,.
NUMBER OF BREEDING TERRITORIES OF SMALL-AND MEDIUM-SIZED UPLAND BIRDS THAT WOULD BE IMPACTED THROUGH HABITAT DESTRUCTION OR-ALTERATION AS A RESULT OF
THE SUSITNA HYDROELECTRIC PROJECT, ALASKA. {NUMBERS WERE DERIVED FROM TilE DENSITIES OF SPECIES TERRITORIES ON THE RESPECTIVE BIRD CENSUS PLOTS IN
1981, MULTIPLIED BY THE AREA OF CORRESPONDING AVIAN HABITAT TO BE AFFECTED BY THE PROJECT [TAKEN FROM PLANT ECOLOGY REPORT, APA 1982].)
WATANA DEVIL CANYON ACCESS TOTAL
Construction Construction
Species Impoundment Zone Total Impoundment Zone Total Total
Spruce Grouse 210 200 410 102 244 346 38 794
IH 11 ow Ptannigan 11 73 84 1 7 8 3 95
Rock Ptannigan '-2 2
Am. Golden Plover 30 30 1 1 3 34
Greater Yellowlegs 4 11 15 5 5 20
COIIUBon Snipe 407 313 720 14 29 43 1 764
least Sandpiper 10 10 1 11
Baird's Sandpiper 20 20 1 1 2 23
Hairy Woodpecker 105 100 205 51 122 -.173 21 399
Downy Woodpecker 1" 1
__, N, 3-toed Woodpecker 395 210 605 78 162 240 13 858
w Alder Flycatcher 3 3 __,
Horned Lark 15 15 2 17
Gray Jay 524 292 816 114 325 439 35 1290
Black-capped Chickadee 5 5
Boreal Chickadee 670 527 1197 151 334 485 52 1734
Brown Creeper 105 100 205 51 122 173 5 383
American Robin 239 185 424 8 41 49 24 497
Varied Thrush 2014 1217 3231 649 1214 1863 174 5268
llenni t Thrush 991 576 1567 492 699 1191 98 2856
Swainson's Thrush 2928 2060 4988 1140 2166 3306 302 8596
Gray-cheeked Thrush 1122 1083 2205 41 190 231 16 2452
Wheatear 2 2 2
Arctic Warbler 476 1747 2223 19 294 313 62 2598
Ruby-crowned Kinglet 3555 2304 5859 538 1110 1648 117 7624
Water Pipit 41 41 2 2 5 48
Yellow-rumped Warbler 3921 2931 6852 1442 2527 3969 367 11,188
Blackpoll Warbler 1207 968 2175 331 493 824 62 3061
Northern Waterthrush 270 253 523 133 307 440 67 1030
Wilson's Warbler 2008 4736 6744 439 1442 1881 236 8861
Common Redpo 11 1196 1182 2378 368 734 1102 115 3595
Savannah Sparrow 1486 4294 5780 50 569 619 157 6556
Dark-eyed Junco 2983 2112 5095 739 1595 2334 209 7638
Tree Sparrow 2803 6777 9580 102 1032 1134 234 10,948
White-crowned Sparrow 1610 2850 4460 62 492 554 74 5088
Fox Sparrow 1621 1363 2984 192 486 678 63 3725
Lapland longspur 34 278 312 4 22 26 17 355
Snow Bunting 15 15 2 17
TOTAL BREEDING PAIRS 32,895 38,875 71,770 7311 16,767 24,078 2588 98,436
are red squirrels and porcupines. While this habitat loss would
constitute a major impact on these species, most are common in the area
(Table 7) and are represented by healthy populations in adjacent
regions.
Flooding of the fluviatile shorelines and alluvia, both in the main
Susitna River and up the mouths of tributary creeks, would destroy
breeding habitat of a few bird species (Harlequin Duck, Common
Merganser, Semipalmated Plover, Spotted Sandpiper, Wandering Tattler~
Arctic Tern, Dipper) and thus reduce their numbers in the Basin. Some
of these species are considered uncommon, but none rare, in the region.
Impact on wintering habitat of the Dipper (open water along fast-running
tributaries and in the Susitna River channel) might be the most serious
impact in this category, because ·local alternative sites of open water
might not be available. Flooding would also deprive early migrant
waterfowl of one of the first sources of open water in the region--the
rapidly flowing waters of the Susitna River. Both of these impacts·
might be alleviated if year-round open water was provided by the project
between Devil Canyon dam and Talkeetna.
The large impoundment that would be formed could provide habitat for
waterbirds, but the degree of utilization would depend upon the rate and
kind of development of food resources in the new lake. Because of the
late spring thaw, the lake would be available only for the late-
migrating diving ducks, loons, and grebes; but in fall it might remain
open long enough to be used by 1 ate-migrating swans. As with the other
large lakes of the region, a low level of use by breeding waterfowl can
be anticipated, provided food resources are available. The drawdown.
zone would impede use of the reservoir edge by nesting loons and grebes,
which usually nest at the edge of sedge shorelines or on small low-lying
islands; but, where narrow, it might not impeGe waterfowl nesting,
because many species nest farther back from the water's edge if
appropriate cover is available. Migrant shorebirds, whose main movement
132
passes through central Alaska during the last three weeks of May, would
probably use exposed areas of the drawdown zone for resting and feeding.
This zone would be an ecological desert for small mammals.
(b) Camp/Villa2e Sites/Construction Zone
Impacts caused by factors other than flooding {e.g., camp/village sites
and borrow areas) would be of two main types: 1) habitat destruction
and alteration and 2) disturbance to animals themselves, especially
birds, by various types of human activities during and after construction.
The "construction zone" (defined by the Plant Ecology report, APA 1982,
as all facilities components except the impoundment) for the Watana
facility would impact almost as much area as the impoundment (13,725 ha
vs 14,691 ha; APA 1982), and would affect the breeding habitat of 39,000
pairs of birds (Table 25). The species subject to the highest losses
would be Tree Sparrow (6800 breeding territories), Wilson•s Warbler
{4700), and Savannah Sparrow (4300), primarily because the construction
zone would impact large areas of upland shrub habitats used by these
common to abundant species. Additionally, the habitat of over 1000
breeding pairs each of another nine bird species would be impacted,
including some using the more restricted forest habitats (Yellow-rumped
Warbler, Ruby-crowned Kinglet, Dark-eyed Junco, Swainson•s Thrush, and
Varied Thrush). The overall effect on the populations of the common
upland shrub-nesting species probably would not be too serious, because
upland shrub habitats are widespread in the region and could probably
absorb the displaced birds. It is unlikely, however, that the displaced
forest-nesting birds could find_ alternative sites in the more restricted
and more heavily impacted forest habitats.
About camp/village sites, ground squirrels could be expected to increase
and become tame, especially if fed by workers, and would probably become
pests. Some birds, too, such as ravens, magpies, and Mew Gulls, would
be attracted to any open refuse dumps.
133
Perhaps more importantly, there could be significant effects on sensitive bird
species and habitats near camp/village sites, primarily on raptors and on
waterbirds and wetland habitats. Increased air traffic over the Fog Lakes
wetlands as a result of activities about the dam site or about the south-side
camp/village site, or over the Stephan-Murder lake area as a result of trips
between Watana and Devil Canyon camps/villages/dam sites, could adversely impact
waterfowl populations. While it is possible that some individuals of some
-"
species might show some habituation to these disturbances, the net result would
be a reduction in the suitability of these areas for raptors and waterfowl.
A few waterbirds, use the small ponds between Deadman and Tsusena creeks, but
because their numbers are small, potential losses caused by human activities
would be minor relative to their overall population levels in the region.
The camp site is adjacent to raptor/raven cliff habitat along Deadman Creek. An
active raven nest and territorial Merlins were observed here in 1981. The
habitat at this location would be flooded, eventually, by the impoundment, so the
major impact would be from proximity to the reservoir rather than to the camp.
The village site is within 1.5 km of a Bald Eagle nest that was active in both
1980 and 1981. While this nest is a borderline distance from the village site
relative to disturbance, activity by future village residents any closer than
this distance would most likely cause the eagles to desert this nesting area.
5.2 -Devil Canyon Dam and Impoundment
(a) Impoundment
The Devil Canyon impoundment would have many of the same effects on bird and
non-game mamma 1 popu 1 at ions· as the Watana impoundment. The impoundment would
flood 27.4 km of the better quality raptor cliffs (type "A 11
), but would leave
24.9 km above waterline. One active and two inactive Golden Eagle nest sites
and one active and one inactive raven site would be testroyed. (Table 21).
As mentioned above, in spite of the presence of cliffs with good
structural characteristics, Devil Canyon is for some reason little used
for raptor nesting. Possibly, the deep, narrow canyon with its often strong
and buffeting winds makes this area undesirable for raptors. With the
134
filling of the deeper, narrow portions of the canyon upstream of the
Devil Canyon dam, the environmental conditions along the remaining type
11 A11 cliffs conceivably could be altered enough to make the cliffs more
a~tractive to raptors and ravens. That is, the remaining canyon would
/
be wider and shallower and perhaps have less violent winds and thus
might-be more hospitable to cliff-nesting birds. If not, birds nesting
in the impoundment area ··waul d be forced elsewhere, either to the
remaining cliffs of the Susitna River and tributaries or to the nearby
cliff-tor habitat of the uplands. Unflooded cliff habitat along Portage
and Devil creeks and others draining into the south side of the proposed
Devi 1 Canyon impoundment (e.g., Cheechako Creek) might become important
to the displaced birds.
In addition to cliff habitat, the Devil Canyon impoundment would destroy
the breeding habitat of over 7000 pairs of small-and medium-sized
upland birds (Table 25), including 21 km 2 of forest habitats, which are
generally the most productive avian habitats of the region (Table 8).
The Swainson•s ·Thrush and Yellow-rumped Warbler, both forest-nesting
species, would each lose over 1100 breeding territories. A number of
other bird species are also restricted to these forest habitats for
breeding (see Table 9), as are red squirrels and porcupines.
Flooding of the fluviatile shorelines and alluvia by the Devil Canyon
impoundment would destroy the breeding habitats of the same bird species
affected by the Watana inundation--Harlequin Duck, Common Merganser,
Semipalmated Plover, Spotted Sandpiper, Wandering Tattler, Arctic Tern,
Dipper--and would similarly impact the wintering habitat of the Dipper
(open water· along fast-running tributaries and in the Susitna River
channel). Flooding would also deprive early migrant waterfowl of one of
the first sources of open water in the region--the rapidly flowing
waters of the Sus itna River--unless waters farther downstream were
available as a result of the project.
135
As with Watana, the Devil Canyon reservoir could provide habitat for
waterbirds, but the degree of utilization would depend upon the rate and
kind of development of food resources in the new lake. Because of the
l-ate spring thaw, the lake would be available only for the late-
~ligrating diving ducks, loons, and grebes; but in fall it might remain
open long enough to be used by late-migrating swans. As wi~h the other
large lakes of the region, a low level of use by breeding waterfowl
could be anticipated, provided food resources are available.
Because of the steep banks and more limited extent of drawdown compared
to the Watana impoundment, the changed shoreline at the Devil Canyon
site probably would not exert the level of impact of Watana. There
would be less waterbird nesting habitat around the impoundment's shore-
line and less drawdown area to attract migrant ~horebirds.
(b) Camp/Village Sites/Construction Zone
The impact of the Devil Canyon camp/village sites would generally be the
same as those at the Watana sites, that is, habitat destruction and
alteration compounded by disruption from human activities during and
after construction. The construction zone for the Devil Canyon facility
would impact almost three times the area of the impoundment (Plant
Ecology report, APA 1982) and would affect the breeding habitat of
17,000 pair·s of birds (Table 25). Since 45 km 2 of forest habitat would
be affected, including 24 km 2 of mixed deciduous-coniferous forest, the
impact waul d be greatest on forest-inhabiting species: Yell ow-rumped
Warbler (2500 breeding territories destr.oyed), Swainson's Thrush (2200),
Dark-eyed Junco ("1600), Varied Thrush (1214), and Ruby-crowned Kinglet
(1100). In addition, over 1000 breeding territories each of two shrub
birds would be affected, Tree Sparrow and Wilson's Warbler.
An active Golden Eagle nest site along the north side of the Susitna
··River, below the dam site, is 1.5 km from the camp site and 1.6 km from
136
the village site. In 1974, a Gyrfalcon nested in Cheechako Creek
Canyon, 2.2 km east of the village site (White 1974). This nest site
was active in 1980 (species unknown) and was inactive in 1981. It is
unlikely that either raptor site would be seriously disturbed by
activities in the Vi9inity of the proposed Devil Canyon camp/village
sites, either because of distances involved or, in the case of the eagle
nest, because of the intervening Susitna River.
No wetlands significant to waterbirds occur in this area, but air
traffic between Devil Canyon and Watana camp/village/dam sites could
adversely impact the relatively important Stephan-Murder Lake wetlands,
especially if overflights were at low elevations AGL. Landing aircraft
on lakes when swans were present would drive them from the lakes
(J. G. King and T. N. Ba"iley, USFWS, pers. comm.).
(c) Dam Site
Cheechako Creek-, the tributary canyon 1.0 km southeast of Devil Canyon
dam site and south-southeast of Borrow G contains raptor cliff habitat.
A Gyrfalcon nested here in 1974 (White 1974), and a Goshawk nested in
birch woods on the east bank in 1981. Raptors would probably be driven
from these sites by construction activities, but ·if care were taken to
avoid damage to the canyon itself, individuals could be expected to
return to nest in the area after activities subside. Human activities
associated with a proposed recreation faci 1 ity in the Cheechako Creek
area, however, would probably cause pennanent desertion of the area by
raptors.
5.3 -Borrow Areas
i'~ining of borrow areas would cause twc main types of impacts: 1) habi-
tat destruction and alterat·ion and 2) direct disturbances due to human
137
activities. The potential effects of borrow mining on the number of
breeding territories of small-and medium-sized upland birds have been
included above under the "Construction zone" discussion of the respec-
tive dam facilities and below under access road. Overall, the amounts
and types elf avian and small mammal habitat that would be impacted by
/
any and an of the possible borrow areas appear small relative to the
availability of these habitats in the region. Some borrow areas would
eventually be flooded anyway, and some (Borrow E) would eventually be
recontoured by subsequent seasonal river action.
The specif·ic effects of borrow mining would vary somewhat at each site,
depending on the types of habitats destroyed and the types that would
remain after construction and reclamation activities. Birds and small
mammals dependent on the destroyed or altered habitats would disappear,
whereas new habitats fanned would increase populations of species that
favor the newly created habitats. Replacement shrub and forest habitats
would be slow in fanning, because of the harsh environment at the eleva-
tions of most of the proposed construction; most of the present woody'
habitats are over 100 years old. Overall impact on forest habitats
would be gt~eater than on shrub habitats, partly because of the.relative
proportions in which each occurs in the region and partly because a high
proportion of the forest habitats, which are already less extensive,
would be inundated by the proposed reservoirs and otherwise affected by
construction zone activities. Thus, the additional loss of forest
habitats·to borrow areas would have more of an impact on the avifauna
than would destruction of relatively prevalent shrub habitats.
The activity and noise surrounding the mining operations might disturb
breeding raptors/ravens at nearby cliffs. Following is a list of the
nest sites within about 1.6 km (1 mile) of the potential borrow areas
and thus potentially subject to disturbance. Any nest sites not in use
by 1 June in any year could be considered. inactive in that year
(Roseneau et al. 1981) and not subject to the impacts of construction
noises and the movement of equipment.
138
{a) Borrow Areas B and D
(i) 40 m and 200m, respectively, from an active raven nest
along Deadman Creek that would eventually be inundated
by Watana impoundment
/
{b) ]arrow Area E
{i) 50 m from Golden Eagle nest site
{ i i) 0. 5 km from two raven nest sites
(c) Borrow Area G
(i) 1.3 km from 1974 Gyrfalcon nest and 1981 Goshawk nest
(d) Borrow Area H (adjacent to Fog Creek)
(i) 0.3 km from raven nest site
(ii) 0.4 km from two unknown species of raptor/raven nest
sites
(iii) 0.8 km from three raven nest sites
(iv) 0.0 km from 1974 Goshawk nest (White 1974}
(e) Borrow Area I
(i) 0.6 km from Golden Eagle nest site
(ii) 1.7 km from a raven nest site and two unknown species of
raptorjraven nest sites in Fog Creek
139
(f) Borrow Areas J and L
{i) 1.0 km and 2.0 km, respectively, from an active raven
nest along Deadman Creek that would eventually be inun-
dated by Watana impoundment
(ii) 50-100m from two Golden Eagle nests that would even-
tually be inundated by Wa tana impoundment
{g) Borrow Area K
(i) 1.6 km from 1981 Goshawk nest and 1974 Gyrfalcon nest
5.4 -Access Route
Construction, maintenance, and use of the access route would have three
main types of impacts: 1) destruction of habitat for the roadbed itself
and alteration of habitat adjacent to the road and in borrow areas,
2) disturbances, such as noise and moving equipment, along the road, and
3) increased access to the region and therefore increased use by humans.
The effect of this last impact on birds and small mammals is undeter-
mined at this time, but would be greatest on the larger birds, including
waterfowl and raptors.
Birds and small mammals dependent on the habitats destroyed or altered
by construction would disappear from the immediate area of the road and
borrow areas, whereas new habitats formed would increase populations of
species that favor the· newly created habitats. Permanently retarded
plant successional dev~lopment, such as that found adjacent to roads and
railroads, would provide habitat for several species of shrubland
sparrows and of small mammal species generally restricted to open
herbaceous-dominant plant communities--arctic ground squirrel, tundra
vole, and meadow vole. Although borrow areas would be revegetated after
140
construction, recovery of shrub and forest habitats would be slow,
because of the harsh environment at the elevations of most of the access
route. Most of the shrub and forest habitats in the upper Susitna River
Basin are 1:>ver 100 years old, although recovery rates might be faster
along Indii:ln River, which is at lower elevations.
Known raptor/raven nest sites within 1.6 km {1 mile) of the access route
or access route borrow pits and thus subject to potential disturbance
are as fallows:
(a) Bald Eagle nest in cottonwood near the junction of Indian and
Susitna rivers is only 500 m from the access road and 100 m
from Borrow Area 1. Proposed development would certainly
cause desertion of this nest site.
(b) Gyrfalcon nest (1974) and Goshawk nest ( 1981) in Cheechako
Creek canyon, just east of Devil Canyon dam site, are about
1.6 km from access road.
(c) Two raven nest sites are within 0.5 km of access road along
Tsusena Creek.
Wetlands l'ikely to be adversely impacted by the access route are pri-
marily those along Indian River and in the Chulitna Pass area.· We have
viewed these only cursorily from the air, so cannot predict specific
impacts or levels thereof in this area. Otherwise, only WB 150
(Swimming Bear Lake), a productive alpine lake east of upper Devil
Creek, appears close enough to be seriously impacted by the northern leg
of the access route. The route, however, could be "fine-tuned 11 to avoid
serious impact to this waterbody.
141
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