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Susitna-Watana Hydroelectric Project Document
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Title:
Waterbird migration, breeding, and habitat use, Study plan Section 10.15 :
Initial study report
SuWa 207
Author(s) – Personal:
Author(s) – Corporate:
Prepared by ABR, Inc.-Environmental Research and Services
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Draft initial study report
AEA-identified series, if specified:
Series (ARLIS-assigned report number):
Susitna-Watana Hydroelectric Project document number 207
Existing numbers on document:
Published by:
[Anchorage : Alaska Energy Authority, 2014]
Date published:
February 2014
Published for:
Alaska Energy Authority
Date or date range of report:
Volume and/or Part numbers:
Study plan Section 10.15
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Draft
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194 p. in various pagings
(including all parts)
Related work(s):
Pages added/changed by ARLIS:
Notes:
The following parts of Section 10.15 appear in separate files: Main report ; Appendices A-S.
All reports in the Susitna-Watana Hydroelectric Project Document series include an ARLIS-
produced cover page and an ARLIS-assigned number for uniformity and citability. All reports
are posted online at http://www.arlis.org/resources/susitna-watana/
Susitna-Watana Hydroelectric Project
(FERC No. 14241)
Waterbird Migration, Breeding, and Habitat Use
Study Plan Section 10.15
Initial Study Report
Prepared for
Alaska Energy Authority
Prepared by
ABR, Inc.—Environmental Research & Services
Anchorage and Fairbanks, Alaska, and Forest Grove, Oregon
February 2014 Draft
INITIAL STUDY REPORT WATERBIRD MIGRATION, BREEDING, AND HABITAT USE STUDY (10.15)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page i February 2014 Draft
TABLE OF CONTENTS
Executive Summary ...................................................................................................................... x
1. Introduction............................................................................................................................ 1
2. Study Objectives .................................................................................................................... 2
3. Study Area .............................................................................................................................. 2
4. Methods and Variances in 2013 ............................................................................................ 3
4.1. Spring and Fall Migration .............................................................................................. 3
4.1.1. Aerial Surveys ......................................................................................................... 3
4.1.2. Ground-based Surveys ............................................................................................ 5
4.2. Breeding Season ............................................................................................................. 9
4.2.1. Breeding Population Surveys .................................................................................. 9
4.2.2. Harlequin Duck Surveys ....................................................................................... 11
4.2.3. Brood Surveys ....................................................................................................... 12
4.3. Information for Mercury Study .................................................................................... 13
4.3.1. Variances............................................................................................................... 13
5. Results ................................................................................................................................... 14
5.1. Spring and Fall Migration ............................................................................................ 14
5.1.1. Aerial Surveys ....................................................................................................... 15
5.1.2. Ground-based Surveys .......................................................................................... 23
5.2. Breeding Season ........................................................................................................... 31
5.2.1. Breeding Population Surveys ................................................................................ 31
5.2.2. Harlequin Duck Surveys ....................................................................................... 35
5.2.3. Brood Surveys ....................................................................................................... 39
5.3. Information for Mercury Study .................................................................................... 40
6. Discussion ............................................................................................................................. 41
6.1. Spring and Fall Migration ............................................................................................ 41
6.1.1. Aerial Surveys ....................................................................................................... 41
6.1.2. Ground-based Surveys .......................................................................................... 43
6.2. Breeding Season ........................................................................................................... 52
6.2.1. Breeding Population Surveys ................................................................................ 52
6.2.2. Harlequin Duck Surveys ....................................................................................... 53
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Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page ii February 2014 Draft
6.2.3. Brood Surveys ....................................................................................................... 54
6.3. Information for Mercury Study .................................................................................... 55
7. Completing the Study .......................................................................................................... 56
8. Literature Cited ................................................................................................................... 56
9. Tables .................................................................................................................................... 61
10. Figures .................................................................................................................................. 87
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Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page iii February 2014 Draft
LIST OF TABLES
Table 4.1-1. Details of Aerial Surveys for Migrating and Breeding Waterbirds, 2013. ............... 61
Table 5.1-1. Status of Waterbird Species Observed during Waterbird Migration and Breeding
Surveys, 2013. ....................................................................................................................... 62
Table 5.1-2. Numbers of Waterbirds Observed on Streams and Water Bodies during Spring and
Fall Migration Surveys, 2013. ............................................................................................... 64
Table 5.1-3. Numbers and Occurrence of Waterbirds during Migration and Breeding Surveys,
2013. ...................................................................................................................................... 66
Table 5.1-4. Numbers of Waterbirds by Species-group Observed on Streams and Water Bodies
during Spring and Fall Migration Surveys, 2013. ................................................................. 68
Table 5-1-5. Seasonal Population Statistics for Water Bodies Surveyed during Spring and Fall
Migration Surveys, 1980–1981 and 2013. ............................................................................. 70
Table 5.1-6. Importance Ranks and Values of Water Bodies Surveyed for Waterbirds during
Spring and Fall Migration Surveys, 1980–1981 and 2013. ................................................... 71
Table 5.1-7. Distribution of Radar Targets Observed between 1.5 km and 6.0 km on 6-km-range
Surveillance Radar. ................................................................................................................ 72
Table 5.1-8. Flight Altitudes of Targets Observed on 1.5-km Vertical Radar. ............................ 73
Table 5.1-9. Seasonal Movement Rates and Movement Patterns of Species Groups Observed
North and South of the Visual Observation Station during Diurnal Visual Survey Periods. 74
Table 5.1-10. Post-sunset Audio-visual Observations of Birds Detected Using Binoculars and
Night-vision Goggles during Spring 2013. ............................................................................ 76
Table 5.1-11. Post-sunset Audio-visual Observations of Birds Detected Using Binoculars and
Night-vision Goggles during Fall 2013. ................................................................................ 77
Table 5.2-1. Mean Density of Waterfowl Observed during Breeding Surveys in Breeding Lake
Groups, 2013. ......................................................................................................................... 78
Table 5.2-2. Number and Density of Waterfowl Observed during Breeding Surveys of Water
Bodies, 2013. ......................................................................................................................... 80
Table 5.2-3. Numbers and Densities of Waterbirds Observed during Breeding-population
Transect Surveys, 2013. ......................................................................................................... 81
Table 5.2-4. Numbers of Harlequin Ducks Observed during Spring Migration Surveys, 2013. .. 82
Table 5.2-5. Numbers of Harlequin Ducks Observed during Pre-nesting Surveys, 2013. ........... 83
INITIAL STUDY REPORT WATERBIRD MIGRATION, BREEDING, AND HABITAT USE STUDY (10.15)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page iv February 2014 Draft
Table 5.2-6. Numbers of Harlequin Ducks Observed during Brood-rearing Surveys, 2013. ....... 84
Table 5.2-7. Numbers of Waterbird Broods Observed on Water Bodies during Brood-rearing
Surveys, 2013. ....................................................................................................................... 85
Table 5.2-8. Age Subclass1 of Duck Broods Observed during Brood-rearing Surveys, 2013. .... 86
LIST OF FIGURES
Figure 3-1. Waterbird Study Area for the Susitna–Watana Hydroelectric Project....................... 88
Figure 4.1-1. Water Bodies Surveyed for Waterbirds during Spring and Fall Migration in the
Chulitna and Gold Creek Corridors, 2013. ............................................................................ 89
Figure 4.1-2. Water Bodies Surveyed for Waterbirds during Spring and Fall Migration in the
Reservoir Inundation Zone and Vicinity, 2013. .................................................................... 90
Figure 4.1-3. Water Bodies Surveyed for Waterbirds during Spring and Fall Migration in the
Denali Corridor, 2013. ........................................................................................................... 91
Figure 4.1-4. Radar and Visual Sampling Area for Ground-based Surveys of Migration, 2013. 92
Figure 4.1-5. Water Bodies Surveyed for Breeding Waterbirds, and Streams Surveyed for
Harlequin Ducks, in the Chulitna and Gold Creek Corridors, 2013. ..................................... 93
Figure 4.1-6. Water Bodies and Transect Lines Surveyed for Breeding Waterbirds, and Streams
Surveyed for Harlequin Ducks, in the Reservoir Inundation Zone and Vicinity, 2013. ....... 94
Figure 4.1-7. Water Bodies Surveyed for Breeding Waterbirds, and Streams Surveyed for
Harlequin Ducks, in the Denali Corridor, 2013. .................................................................... 95
Figure 5.1-1. Locations and Maximum Number of Waterbirds Observed on Rivers and Water
Bodies during Spring Migration Surveys, 2013. Locations are centerpoints of water bodies
and midpoints of sections of river. ........................................................................................ 96
Figure 5.1-2. Locations and Maximum Number of Waterbirds Observed on Water Bodies
during Fall Migration Surveys, 2013. Locations are centerpoints of water bodies. .............. 97
Figure5.1-3. Spring Diurnal and Nocturnal Passage Rates by Date for Targets Detected within
the 1.5-km Radar Range. Asterisks indicate that no radar sampling occurred due to weather.
............................................................................................................................................... 98
Figure 5.1-4. Passage Rates of Targets, Grouped by Time of Day, during Spring and Fall
Migration, for Targets Detected within the 1.5-km Radar Range. ........................................ 99
INITIAL STUDY REPORT WATERBIRD MIGRATION, BREEDING, AND HABITAT USE STUDY (10.15)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page v February 2014 Draft
Figure 5.1-5. Passage Rates Relative to Hour Post-Sunset During Spring and Fall Migration,
for Targets Detected within the 1.5-km Radar Range. ........................................................ 100
Figure 5.1-6. Diurnal and Nocturnal Flight Directions of Targets Detected within the
1.5-km Radar Range. ........................................................................................................... 101
Figure 5.1-7. Radar Targets Detected >1.5 km from the Sampling Station during Spring
and Fall Migration. .............................................................................................................. 102
Figure 5.1-8. Mean Diurnal and Nocturnal Flight Altitudes of Targets during Spring
Migration, by Date for Targets Detected within the 1.5-km Radar Range. ......................... 103
Figure 5.1-9. Mean Flight Altitudes of Targets, Grouped by Time of Day, during Spring and
Fall Migration for Targets Detected within the 1.5-km Radar Range. ................................ 104
Figure 5.1-10. Mean Movement Rates of Passerines by Week of the Spring and Fall
Migration Survey Seasons. .................................................................................................. 105
Figure 5.1-11. Mean Movement Rates of Waterbirds by Week of the Spring and Fall
Migration Survey Seasons. .................................................................................................. 106
Figure 5.1-12. Mean Movement Rates of Raptors by Week of the Spring and Fall Migration
Survey Seasons. ................................................................................................................... 107
Figure 5.1-13. Mean Movement Rates of Sandhill Cranes by Week of the Spring and Fall
Migration Survey Seasons. .................................................................................................. 108
Figure 5.1-14. Mean Movement Rates of Bird Groups by Time of Day during Spring
Migration Survey Season. .................................................................................................... 109
Figure 5.1-15. Flight Altitude Categories for Species Groups Observed during Diurnal
Visual Surveys in Spring. .................................................................................................... 110
Figure 5.1-16. Ordinal Flight Directions of Bird Flocks Observed during Spring Diurnal
Visual Surveys. .................................................................................................................... 111
Figure 5.1-17. Fall Diurnal and Nocturnal Passage Rates by Date for Targets Detected within
the 1.5-km Radar Range.. .................................................................................................... 112
Figure 5.1-18. Mean Diurnal and Nocturnal Flight Altitudes of Targets during Spring
Migration, by Date for Targets Detected within the 1.5-km Radar Range. ......................... 113
Figure 5.1-19. Mean Movement Rates (birds/h) of Bird Groups by Time of Day during Fall
Migration Survey Season. .................................................................................................... 114
Figure 5.1-20. Flight Altitude Categories for Species Groups Observed during Diurnal Visual
Surveys in Fall. .................................................................................................................... 115
INITIAL STUDY REPORT WATERBIRD MIGRATION, BREEDING, AND HABITAT USE STUDY (10.15)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page vi February 2014 Draft
Figure 5.1-21. Ordinal Flight Directions of Bird Flocks Observed during Fall Diurnal Visual
Surveys. ............................................................................................................................... 116
Figure 5.2-1. Locations of Harlequin Ducks Observed during Spring Migration Surveys,
2013. .................................................................................................................................... 117
Figure 5.2-2. Locations of Harlequin Duck Observed during Pre-nesting Surveys, 2013. ........ 118
Figure 5.2-3. Locations of Harlequin Duck Observed during Brood-rearing Surveys, 2013. .... 119
Figure 5.2-4. Locations and Numbers of Waterbird Broods Observed during Brood-rearing
Surveys, 2013. ..................................................................................................................... 120
APPENDICES
Appendix A: Documentation of Consultation Among AEA, ABR, USFWS, and ADF&G
Regarding Radar and Visual Migration Sampling Protocols Proposed in the RSP.
Appendix B: Numbers of Waterbirds by Species Observed During Spring and Fall Migration
Surveys, 2013.
Appendix C: Abundance and Percentages of Birds Recorded During Diurnal Audio-Visual
Observations in Spring and Fall 2013.
Appendix D: Flight Lines for Swans Observed During Spring Diurnal Visual Surveys.
Appendix E: Flight Lines for Waterfowl Observed During Spring Diurnal Visual Surveys.
Appendix F: Flight Lines for Eagles Observed During Spring Diurnal Visual Surveys.
Appendix G: Flight Lines for Raptors Observed During Spring Diurnal Visual Surveys.
Appendix H: Flight Lines for Sandhill Cranes Observed During Spring Diurnal Visual Surveys.
Appendix I: Flight Lines for Shorebirds Observed During Spring Diurnal Visual Surveys.
Appendix J: Flight Lines for Loons and Larids Observed During Spring Diurnal Visual Surveys.
Appendix K: Flight Lines for Swans Observed During Fall Diurnal Visual Surveys.
Appendix L: Flight Lines for Waterfowl Observed During Fall Diurnal Visual Surveys.
Appendix M: Flight Lines for Eagles Observed During Fall Diurnal Visual Surveys.
Appendix N: Flight Lines for Raptors Observed During Fall Diurnal Visual Surveys.
Appendix O: Flight Lines for Sandhill Cranes Observed During Fall Diurnal Visual Surveys.
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Susitna-Watana Hydroelectric Project Alaska Energy Authority
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Appendix P: Flight Lines for Loons and Larids Observed During Fall Diurnal Visual Surveys.
Appendix Q: Relative Abundance and Peak Dates of Occurrence of Avian Species Groups from
Selected Alaska Spring Migration Studies.
Appendix R: Relative Abundance and Peak Dates of Occurrence of Avian Species Groups from
Selected Alaska Fall Migration Studies.
Appendix S: Flight Altitudes of Avian Species from Visual Observations During Selected Alaska
Migration Studies.
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LIST OF ACRONYMS, ABBREVIATIONS, AND DEFINITIONS
Abbreviation Definition
ABR ABR, Inc.—Environmental Research & Services
ADF&G Alaska Department of Fish and Game
agl above ground level
AEA Alaska Energy Authority
ANOVA Analysis of Variance
AOU American Ornithologists’ Union
APA Alaska Power Authority
CIRWG Cook Inlet Regional Working Group
CSD circular standard deviation
CUROL Clemson University Radar Ornithology Lab
CWS Canadian Wildlife Service
ESM1 Watana Camp Meteorological Station
df degrees of freedom
FERC Federal Energy Regulatory Commission
ft foot, feet
GHz gigahertz
GIS Geographic Information System
GPS Global Positioning System
GVEA Golden Valley Electric Association
h hour
ha hectares
ILP Integrated Licensing Process
ISR Initial Study Report
km kilometer
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Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page ix February 2014 Draft
Abbreviation Definition
kt knots
kW kilowatt
m meter
µsec microsecond
mi mile
min minute
mi/h miles per hour
m/s meters per second
PAD Pre-application Document
PRM Project River Mile
Project Susitna-Watana Hydroelectric Project
QA/QC Quality Assurance/Quality Control
r mean vector length
RSP Revised Study Plan
SE Standard Error
SPD Study Plan Determination
USFWS U.S. Fish and Wildlife Service
USGS U.S. Geological Survey
V volts
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Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page x February 2014 Draft
EXECUTIVE SUMMARY
Waterbird Migration, Breeding, and Habitat Use 10.15
Purpose The goal of the Waterbird Migration, Breeding, and Habitat Use Study is to
collect baseline data on waterbirds migrating through and breeding in the
Project area to enable assessment of the potential impacts of the Project and to
inform the development of appropriate protection, mitigation, and
enhancement measures.
Status The first year of data collection and analysis was completed successfully in
2013.
Study
Components
This multi-year study consists of the following components:
1. Aerial surveys of water bodies during the spring and fall migration
periods throughout a large study area;
2. Ground-based visual and radar surveys of diurnal and nocturnal avian
migration at a sampling site near the proposed Watana dam location;
3. Aerial surveys for breeding waterfowl;
4. Aerial stream surveys for Harlequin Ducks during the pre-nesting and
brood-rearing periods;
5. Aerial brood-rearing surveys for other waterbirds; and
6. Collection of tissue samples for laboratory analysis of mercury levels.
2013 Variances For aerial surveys, the number of surveys flown during migration was reduced
by three surveys during spring and two surveys during fall to maintain a 5-day
interval between surveys, each of which typically required more than one day
to complete (RSP Section 10.15.4.1.1).
The “breeding-pair survey” proposed in the Study Plan (RSP Section
10.15.4.2.1) was replaced with “breeding population survey,” which is a more
inclusive survey method.
Harlequin Duck surveys were restricted to 10 river miles beyond the study
area buffer due to logistical constraints (RSP Section 10.15.4.2.2).
After further clarification of the scope, objectives, limitations, and historical
justification of the ground-based visual and radar methodologies proposed in
the Study Plan, USFWS dropped its recommendation (which was accepted by
FERC in the February 1 Study Plan Determination) for use of four observers
for visual surveys during migration studies, so visual surveys were conducted
using a single observer, as originally described in RSP Section 10.15.4.1.2.
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The Study Plan study objective for acquiring tissue samples of piscivorous
waterbirds for laboratory analysis of mercury levels, which was based on
opportunistically finding nests during breeding aerial surveys and visiting
those nests after the nesting season to collect feather samples (RSP Section
10.15.4.3), was not met during the 2013 study season. Fewer nests of
piscivorous waterbirds were found than expected during breeding aerial
surveys in 2013.
Steps to
Complete the
Study
As explained in the cover letter to this draft ISR, AEA’s plan for completing
this study will be included in the final ISR filed with FERC on June 3, 2014.
Highlighted
Results and
Achievements
Distribution, abundance, relative use of water bodies, and timing of arrival,
nesting and departure were documented for waterbirds in the study area in
2013. Overall movement rates as well as those of focal species groups were
moderate-to-low relative to those reported for other migration studies in the
region.
INITIAL STUDY REPORT WATERBIRD MIGRATION, BREEDING, AND HABITAT USE STUDY (10.15)
Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 1 February 2014 Draft
1. INTRODUCTION
On December 14, 2012, the Alaska Energy Authority (AEA) filed with the Federal Energy
Regulatory Commission (FERC or Commission) its Revised Study Plan (RSP) for the Susitna-
Watana Hydroelectric Project No. 14241 (Project), which included 58 individual study plans
(AEA 2012). Section 10.15 of the RSP described the Waterbird Migration, Breeding, and Habitat
Use Study (Waterbird Study). This study focuses on aerial surveys of water bodies during spring
and fall migration, surveys of diurnal and nocturnal migration using visual and radar sampling,
breeding waterfowl population surveys, stream surveys for Harlequin Ducks, and brood-rearing
surveys. RSP Section 10.15 described the goals, objectives, and methods proposed for data
collection on waterbirds.
On February 1, 2013, FERC staff issued its study plan determination (February 1 SPD) for 44 of
the 58 studies, approving 31 studies as filed and 13 with modifications. RSP Section 10.15 was
one of the 13 studies approved with modifications. In its February 1 SPD, FERC recommended
the following:
FWS recommends that the study be modified to clarify that visual observation (both
diurnal and nocturnal) to be conducted along each of the four transects would done by a
separate observer during each sampling session. In other words, four observers would be
used to collect data during each sampling session. FWS also recommends that the study
be modified to clarify that the maximum number of possible 1-hour radar sampling
sessions would be conducted each night because the start and stop time is not currently
specified in the study plan.
AEA states in the study plan that the migration study (which also will provide data for the
Landbird and Shorebird Migration, Breeding and Habitat Use Study [study10.16]) would
require a crew of four biologists working day and night shifts over a period of 120 days
in 2013. While AEA’s study plan suggests that it plans to conduct the study as
recommended by FWS, the plan is not explicit. Using four biologists to concurrently
document birds observed in each direction would ensure better correlation and
interpretation of visual observations with radar data. Although the study plan does not
explicitly state the start and stop times for radar sampling sessions, the plan is clear as to
the sampling framework and that efforts are intended to maximize sampling sessions.
We recommend that AEA implement the study with FWS’ proposed modification for
clarifying the use of four observers during visual observations. No modification of the study
plan is needed regarding maximizing the number of radar sessions because AEA’s study plan
already provides for maximizing the number of radar sessions.
As described below under the radar and visual migration sampling task (see Section 4.1.2.1),
following the February 1 SPD AEA’s study team engaged in further consultation with the U.S.
Fish and Wildlife Service (USFWS) regarding FERC staff’s recommendation. This consultation
resulted in USFWS vacating its original recommendation that was adopted by FERC staff (see
Appendix A). As a result, the visual migration observations were conducted as originally
described in the RSP (Section 10.15.4.1.2).
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Susitna-Watana Hydroelectric Project Alaska Energy Authority
FERC Project No. 14241 Page 2 February 2014 Draft
Following the first study season, FERC’s regulations for the Integrated Licensing Process (ILP)
require AEA to “prepare and file with the Commission an initial study report describing its
overall progress in implementing the study plan and schedule and the data collected, including an
explanation of any variance from the study plan and schedule.” (18 CFR 5.15(c)(1)) This Initial
Study Report (ISR) on the Waterbird Study has been prepared in accordance with FERC’s ILP
regulations and details AEA’s status in implementing the study, as set forth in the FERC-
approved RSP (referred to herein as the “Study Plan”).
Following the standard practice of the American Ornithologists’ Union (AOU 1998), the names
of bird species are capitalized throughout this report.
2. STUDY OBJECTIVES
The goal of the Waterbird Study is to collect baseline data on waterbirds migrating through and
breeding in the Project area and surrounding study area to enable assessment of the potential
impacts of the Project and to inform the development of appropriate protection, mitigation, and
enhancement measures. As used here, “waterbirds” is applied broadly to include swans, geese,
ducks, loons, grebes, cranes, cormorants, herons, gulls, and terns. Shorebirds frequently are
included in the general category of waterbirds, but they are addressed separately for this Project
under the Landbird and Shorebird Migration, Breeding, and Habitat Use Study (Study 10.16)
because the ground-based survey methods for shorebirds are similar to those used for landbirds.
The Study Plan for the Waterbird Study includes breeding surveys for the Harlequin Duck, a
species of conservation concern that requires specific stream-survey techniques.
This study has three objectives, as established in RSP Section 10.15.1:
• Document the occurrence, distribution, abundance, habitat use, and seasonal timing of
waterbirds migrating through the Project area in spring and fall.
• Document the occurrence, distribution, abundance, productivity, and habitat use of
waterbirds breeding in the Project area.
• Review available information to characterize food habits and diets of piscivorous
waterbirds documented in the study area as background for the Mercury Assessment and
Potential for Bioaccumulation Study (Study 5.7).
The information gained from this study will be used to evaluate waterbird habitat loss and
alteration quantitatively, in conjunction with the separate Vegetation and Wildlife Habitat
Mapping Study and the Evaluation of Wildlife Habitat Use Study (see Studies 11.5 and 10.19,
respectively), and to estimate the number of migrating and breeding waterbirds that may be
affected by the Project.
3. STUDY AREA
As established in RSP Section 10.15.3, the study area for waterbirds encompasses lakes, ponds,
rivers, streams, and flooded wetlands within a 3-mi (4.8-km) buffer area around the proposed
Watana reservoir, the Watana Dam Site and Camp Facilities Area, and the alignments of the
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three road and transmission corridors (Figure 3-1). The 3-mi buffer includes nearly all of the
water bodies surveyed in the 1980s for the Alaska Power Authority (APA) Susitna Hydroelectric
Project (Kessel et al. 1982), most of which occur in relatively discrete groupings (e.g., see Pre-
Application Document [PAD] Figure 4.6-16; AEA 2011). The study area boundary extends
beyond 3 mi in several places to include other water bodies surveyed by Kessel et al. (1982),
such as Stephan Lake, Murder Lake, Clarence Lake, and other unnamed water bodies south of
the Susitna River between Kosina Creek and the Oshetna River, but six large lakes (Kessel’s
numbers 131–136) between the mouths of the Tyone and Maclaren rivers are not included in the
study area because they are located well upstream from the area that may be affected by the
Project.
4. METHODS AND VARIANCES IN 2013
The methods of data collection and analysis described in RSP Section 10.15.4 were followed
during the spring, summer, and fall field surveys in 2013, although some variances from the
methods proposed in the Study Plan were necessary because of survey logistics and further
consultation with the USFWS after the Commission’s February 1 SPD. The methods, variances
and justification for variances from the Study Plan are described in each relevant subsection
below.
4.1. Spring and Fall Migration
4.1.1. Aerial Surveys
AEA implemented the methods described in the Study Plan, with the exception of variances
explained below (Section 4.1.1.1).
Waterbirds use a broad range of lakes, ponds, rivers, creeks, and flooded wetlands throughout the
study area during migration. The most effective means of assessing the distribution and
abundance of waterbirds over such a large area is by aerial survey. Waterbirds often use rivers
and streams for staging during early spring when water bodies are covered by ice, so spring
surveys were flown parallel to river and stream courses, in addition to covering lakes and ponds.
In contrast, fall migration surveys included only lakes, ponds, and flooded wetlands. Because of
the distribution of water bodies in relatively discrete, irregularly spaced groupings in most of the
study area, a lake-to-lake survey pattern was the most efficient survey approach, in which the
survey path either circled or bisected each water body to allow survey personnel to count
waterbirds in the water and on the shore.
Rather than specifying a minimum water body size to be surveyed for the lake-to-lake surveys,
the survey team delineated an efficient flight path through and among water-body groups to
maximize the number of water bodies covered within the 3-mi buffer of the study area. A route
covering all water bodies in a lake group was repeated on each migration survey using Global
Positioning System (GPS) navigation. The survey route was developed by reviewing U.S.
Geological Survey (USGS) 1:63,360-scale topographic maps and high-resolution aerial or
satellite imagery. Most water bodies 5 acres (2 ha) or more in size were surveyed, as well as
many smaller ponds located between larger water bodies. This approach provided more complete
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survey coverage than would have resulted from selection of a random sample of water bodies in
the study area.
Before field surveys began, large lakes (>50 acres) and groups of smaller lakes (<50 acres each)
were allocated among various lake-survey groups and sections of rivers were assigned unique
identification numbers (Figures 4.1-1, 4.1-2, and 4.1-3). The centroids of lakes and lake groups
and the end points of river sections were used as waypoints and were loaded into a global
positioning system (GPS) receiver to aid the pilot in navigating to survey locations. The survey
team created field maps showing survey lakes and rivers on a topographic base layer and used
them, together with the GPS, to visually navigate to survey locations. Flight lines on each survey
were recorded on a GPS receiver.
To characterize the period of migration adequately and avoid missing migration peaks for
various species and species-groups of waterbirds, surveys were conducted at five-day intervals
during the spring (late April to late May) and fall (mid-August to mid-October) migration
periods, resulting in 7 surveys in spring and 11 surveys in fall (Table 4.1-1). Each survey took
one to three days to complete, depending on weather conditions and, during spring, on the extent
of open water. The first fall migration survey was combined with the second Harlequin Duck
brood-rearing survey; together, those two surveys took five days to complete. The spring
migration surveys transitioned directly into the waterfowl breeding population surveys with no
break in timing, as is described below (Section 4.2.1).
The aircraft used on all aerial surveys was a small, piston-engine helicopter (Robinson R-44).
Surveys were flown at 125–200 ft above ground level and a speed of 20–45 kt when observing
waterbirds. An experienced biologist recorded all data on a hand-held digital recorder, including
GPS waypoint number; lake group or river identification number; and the number, species, and
sex of birds. Nests and broods were recorded whenever encountered. After each survey, the
observation recordings were either transferred directly into a digital database or were transcribed
onto data sheets for later entry into the database. Observation recordings were reviewed a second
time and compared with the digital database during quality assurance/quality control (QA/QC)
review. Data were summarized by species, species group, location (water body or stream), date
of survey, and survey area. Species-groups used for data summaries included waterfowl (geese,
swans, dabbling ducks, and diving ducks), loons, grebes, cranes, gulls, terns, and jaegers. Some
closely related waterfowl species that are difficult to differentiate during aerial surveys (e.g.,
Lesser vs. Greater scaup, Common vs. Barrow’s goldeneyes) were recorded to the lowest
taxonomic level of identification possible.
During data analysis, the study team compiled data on species composition, summarized the
timing of migration, and identified water bodies that were important to migrating waterbirds. For
the latter task, the team followed the approach used to analyze migration data for the 1980s APA
Susitna Hydroelectric Project (Kessel et al.1982): a “relative importance value” was calculated
for a specific subset of water bodies to evaluate their use by waterbirds during spring and fall
migration. First, the area of water bodies sampled was measured using a geographic information
system (GIS). Next, the relative importance value of each lake was calculated as the sum of the
relative mean abundance (number of birds) from the spring or fall surveys, the relative mean
density (birds/km²), and the relative mean species richness (number of species). For the subset of
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water bodies that were sampled in both studies, the relative importance values from the 2013
surveys were compared with those reported by Kessel et al. (1982).
4.1.1.1. Variances
Fewer migration surveys were conducted during spring and fall in 2013 than were described in
RSP Section 10.15.4.1.1. A five-day interval was scheduled between successive surveys, as
stated in the RSP. However, when surveys took two or more days to complete, the five-day
interval between surveys was calculated from the ending day of one survey to the first day of the
next survey, rather than from the start of one survey to the start of the subsequent survey, as had
been done when estimating the number of surveys for the RSP. This adjustment in temporal
spacing resulted in fewer surveys. Despite this adjustment, peak movements of waterbird species
were successfully documented, and study objectives were met in 2013.
4.1.2. Ground-based Surveys
AEA implemented the methods described in the Study Plan, with the exception of variances
explained below (Section 4.1.2.1).
To obtain information on the volume and flight directions of birds migrating through the study
area near the proposed dam site, the study team conducted intensive, ground-based surveys of
bird migration in spring and fall by using a combination of visual observations and radar
monitoring. The sampling site and associated field camp for the migration surveys were
established at the peak elevation (709 m [2,325 ft]) of the benchland northwest of the proposed
Watana dam site (Figure 4.1-4). Although this study component is reported here in the Waterbird
Study ISR (ISR Study 10.15), it is important to note that the sampling design also provided
migration data on landbirds, shorebirds, and raptors, which are included in this report for
convenience, rather than being split up among this ISR and those for Studies 10.14, Surveys of
Eagles and Other Raptors, and 10.16, Landbird and Shorebird Migration, Breeding, and Habitat
Use.
Diurnal visual observations were conducted during daylight hours (sunrise to sunset) from April
20 to June 3 (spring migration) and from August 16 to October15 (fall migration) in 2013. Using
binoculars and spotting scopes, individual observers recorded data from an observation point
adjacent to the Watana Camp Meteorological Station (ESM1) during 25-minute sampling
sessions, separated by 5-minute break periods during which weather data were recorded. Data
recorded for each bird observation included date, time, species (or taxon), flock size, transect
crossed (four transect lines, oriented in each of the cardinal directions—north, east, south, west),
distance crossed (distance from observer), flight direction, flight behavior, and an estimate of
minimal flight altitude above the ground.
Nocturnal audiovisual surveys were conducted during the first 2–3 h of nocturnal radar sampling
in both spring and fall to supplement radar data with identification of taxa composing radar
targets. These surveys consisted of 50-min sessions of visual sampling by a single observer,
concurrent with hourly radar sampling. The timing of the visual sampling period was adjusted as
day length changed during the migration periods. Observers used binoculars during crepuscular
(twilight) periods and night-vision goggles, aided by infrared spotlights to illuminate targets
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flying overhead, during dark periods. For each bird or flock of birds detected, observers collected
the following data: species or taxon, flight direction, flight altitude, flight behavior, and transect
(north, east, south, or west). Weather data recorded during each visual and/or radar sampling
session included wind direction, average wind speed, cloud cover, ceiling height, light
conditions, precipitation, air temperature, and barometric pressure. These weather data
supplemented hourly weather data summaries collected by the ESM1 station.
For radar monitoring of flight activity, the survey team set up a portable marine radar, which
functioned in both surveillance and vertical modes, near the field camp, approximately 120 m
(400 ft) north–northwest of the visual observation point. The radar was powered by a portable
generator and two 12V batteries. The radar (Furuno Model FR-1510 MKIII; Furuno Electric
Company, Nishinomiya, Japan) is a standard X-band marine radar transmitting at 9.410 GHz
through a 2-m-long slotted wave guide (antenna), with a peak power output of 12 kW. The
antenna has a beam width of 1.23° (horizontal) × 25° (vertical) and a side lobe of ±10–20°.
Range accuracy is 1 percent of the maximal range of the scale in use or 30 m (whichever is
greater) and bearing accuracy is ±1°. A pulse length of 0.07 µsec was used while operating at the
1.5-km (0.9-mi) range to sample the flight activity of small-bodied birds, such as songbirds. A
longer pulse length (0.5 µsec) was used while operating at the 6-km (3.7-mi) range to sample the
flight activity of large-bodied birds, such as waterfowl, cranes, and raptors. At shorter pulse
lengths, echo resolution is improved (giving more accurate information on target identification,
location, and distance), whereas at longer pulse lengths, echo detection is improved (increasing
the probability of detecting a target). An echo is a picture of a target on the radar monitor and a
target is one or more birds (or bats) that are flying so close together that the radar displays them
as one echo on the display monitor. The radar has a digital color display with several useful
features, including true north correction for the display screen (to evaluate flight directions),
color-coded echoes (to differentiate the strength of return signals), and on-screen plotting of a
sequence of echoes (to depict flight paths). Because targets are plotted with every sweep of the
antenna (2.5-sec intervals) and because groundspeed is directly proportional to the distance
between consecutive echoes, a hand-held scale was used to estimate ground speeds of plotted
targets to the nearest 5 km/h (3.1 mi/h) when operating at the 1.5-km range and to the nearest 20
km/h (12 mi/h) during operation at the 6-km range.
Radar data were collected in 1-h sampling sessions throughout each night (from shortly after
sunset to just before sunrise) and in 3-h blocks during the day (between sunrise and sunset).
Diurnal sampling blocks varied each day to maximize evenness of sampling effort for each hour
across the season. Each 1-h radar sampling session consisted of (1) one 10-min period to collect
weather data and adjust the radar to surveillance mode; (2) one 10-min period with the radar in
surveillance mode (1.5-km range) to collect information on migration passage rates of small-
bodied birds (e.g., passerines, shorebirds); (3) one 10-min period with the radar in surveillance
mode (1.5-km range) to collect information about flights of small-bodied birds, including
groundspeed, flight direction, tangential range (minimal perpendicular distance to the radar
laboratory), transect crossed (north, south, east, and west), and the number of individuals (if
known); (4) one 10-min period with the radar in surveillance mode (6-km range) to collect
information on both passage rates of large-bodied birds and information on their groundspeed,
flight direction, tangential range (minimal perpendicular distance to the radar), transect crossed
(north, south, east, and west), and the number of individuals (if known); (5) one 5-min period to
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adjust the radar to vertical mode; and (5) one 15-min period with the radar in vertical mode (1.5-
km range) to collect information on flight altitudes and flight behavior. All hours of radar data
were recorded using an automated image frame-recording device (Model VGA2USB, Epiphan
Systems Inc., Ottawa, Ontario), which enabled continuous collection of a record of high-quality
lossless radar images, with a resolution identical to that of the radar monitor.
Data collected in this study on flight volume, altitudes, and directions among all species and taxa
were summarized for comparison with the results of similar studies conducted in Alaska at Tok,
in the upper Tanana River valley, and Gakona, in the Copper River valley (Cooper et al. 1991a,
1991b; Cooper and Ritchie 1995);the Tanana Flats and Alaska Range foothills near Healy (Day
et al. 2007; Shook et al. 2006, 2011);and Fire Island in upper Cook Inlet (Day et al. 2005).Visual
observation analyses were differentiated among species-groups and subgroups of particular
interest (swans, cranes, and eagles). Common Ravens were excluded from analyses of passerine
species because of differences in their flight behaviors and the range of detectability for both
horizontal distances and flight altitudes. In the radar data, targets observed >1.5 km from the
radar represented larger bird species, composed primarily of raptors, cranes, and waterfowl
during diurnal sessions and waterfowl during nocturnal hours.
Data from diurnal visual surveys during spring and fall were used to calculate movement rates
based on the number of birds observed in flight from the visual observation station. Daily visual
movement rates are reported as the mean number of birds/h ±1 standard error (SE) and are not
adjusted for detectability of different size-classes of birds by distance. Flocks are used as the
summary unit for flight direction and flight altitude. When summarizing flight direction, only
birds exhibiting straight-line flight for a distance of at least 100 m were included, and directions
are reported as medians for categories of cardinal and intermediate directions (e.g. north,
northeast, east, southeast, south, southwest, west, northwest). The minimum flight altitude
observed for each individual or flock was reported. Because of limitations in the accuracy of
altitude estimates at greater distances, flight altitudes were analyzed only for those flocks
observed within 1 km (horizontal distance) of the visual observation station.
Based on previous studies, the primary axis of migration in the region was presumed to be east–
west. The cross-sectional distribution of migration across the basin was assessed by comparing
movement rates of birds crossing transect lines extending north and south of the visual
observation station. For birds with directional flight that were not observed crossing a transect,
transect crossings were estimated by extrapolating flight lines. In cases where multiple cardinal
transects were crossed, targets were assigned to a primary transect (north or south) line. To
determine if differences in movement rates north and south of the station resulted from birds
preferentially following the Susitna River channel, the numbers of flocks crossing a 1.5-km
transect line due south of the observation station (extending the full width of the river channel at
the site) were compared with the numbers crossing a 1.5-km transect line extending due north
(away from the channel).
Of primary importance in radar target identification is the elimination of insect targets. Insect
contamination was reduced by (1) omitting small targets (the size of gain specks) that only
appeared within ~500 m of the radar, as well as targets with poor reflectivity (e.g., targets that
plotted erratically or inconsistently in locations having good radar coverage); and (2) editing data
before analysis by omitting targets with corrected airspeeds <6 m/s (<13.4 mi/h). This threshold
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was based on radar studies that determined that most insects have airspeeds of <6 m/s, whereas
those of birds and bats usually are >6 m/s (Tuttle 1988, Larkin 1991, Bruderer and Boldt 2001,
Kunz and Fenton 2003). Airspeeds of surveillance-radar targets were calculated using ground
speed and flight direction, corrected for concurrent wind velocity and wind direction obtained
from the ESM1 station (see Mabee et al. 2006). Targets that had corrected airspeeds <6 m/s were
omitted from all analyses of surveillance radar. Use of the radar in vertical mode to obtain flight
altitude data results in a tradeoff between maximizing sample sizes and maximizing the number
of targets for which actual ground speeds can be discerned. To obtain adequate sample sizes for
analysis of flight altitudes, the threshold airspeed criterion was used for targets only on dates
when insects or insect-like radar targets were detected, under the assumption that all targets were
birds on dates with no insects or insect-like targets were observed.
Unlike movement rates based on visual observations of all birds observed in flight, radar passage
rates provide an index of migration densities and are reported as the mean number ± 1 SE of
targets passing along 1 km of migratory front per hour. All radar flight-altitude data are reported
in meters above ground level (m agl) relative to a horizontal plane passing through the radar-
sampling station. Actual mean altitudes may be higher than those reported because an unknown
number of birds fly above the 1.5-km range limit of the radar (Mabee and Cooper 2004). Flight-
direction data were analyzed following procedures for circular statistics with Oriana software
version 3.1 (Kovach 2009). Mean and median flight directions of radar targets were calculated,
as well as the circular standard deviation (CSD) and the mean vector length (r) to describe the
dispersion of flight directions. Mean flight directions coupled with high r values (maximum = 1)
indicate strong patterns in flight orientation, whereas mean flight directions coupled with low r
values (minimum = 0) indicate weak or no directionality in flight movements.
To assess daily patterns in migration passage rates and flight altitudes, the study team assumed
that a day began at sunrise, so that sampling nights were not split between two dates. For both
radar and visual studies, diurnal sampling periods were categorized as morning (sessions starting
<4 h post-sunrise), late afternoon (sessions starting <4 h pre-sunset), and mid-day (all other
sessions). Differences among time periods in passage rates (radar and visual) and flight altitudes
(radar only) were analyzed using one-way analysis of variance (ANOVA; SPSS 2010). For radar
surveys, one-way ANOVA also was used to examine differences among passage rates and flight
altitudes of targets during sessions occurring within 1 h after sunset and 1 h before dawn, and
during the nocturnal hours between these crepuscular hours. Repeated-measures ANOVAs,
incorporating the Greenhouse–Geisser epsilon adjustment for degrees of freedom (SPSS 2010),
were used to compare passage rates among hours during night when data were collected in the
first 4 h after sunset in the spring and the first 7 h after sunset in the fall, due to differences in the
minimum number of nocturnal hours during of each season.
In the diurnal visual surveys, the cross-sectional distribution of migration across the basin was
assessed by comparing passage rates of targets crossing transect lines north and south of the
radar sampling station. When necessary, transect crossings were assigned to targets with short,
unidirectional flight paths by extrapolating flight paths across transects. In cases where multiple
transects were crossed, targets were assigned to a primary transect (north or south) line. For
targets observed during sampling at the 1.5-km range, passage rates of targets north and south of
the station were compared using paired t-tests (SPSS 2010); the distributions of targets observed
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crossing the north and south transects >1.5 km from the radar also were compared from sampling
at the 6-km range.
Factors that decreased sample sizes of the various summaries and analyses of radar data included
insect contamination, precipitation, logistical issues, and variable numbers of hours of darkness
across the season. Therefore, sample sizes sometimes differ among summaries and analyses.
4.1.2.1. Variances
Following a meeting on March 1, 2013, the USFWS reversed its recommendation for
modification of the RSP, which had been accepted by FERC in the February 1 SPD. The
suggested modification called for the use of four visual observers during both diurnal and
nocturnal sampling periods, rather than the single observer proposed in the RSP. Through further
consultation with USFWS on March 1, however, the AEA study team provided clarification of
the scope, objectives, limitations, and historical justification of the visual and radar
methodologies proposed, as well as contingencies for alternative methods to be used in case
individual observers determined that conditions warranted modifications to increase sampling
efficiency. USFWS deemed this additional information sufficient to drop its recommendation for
four simultaneous visual observers (M. DeZeeuw, USFWS Acting CPA/Energy Coordinator,
email communication, March 22, 2013; Appendix A) and the study was conducted, meeting all
objectives, using single visual observers as originally proposed in RSP Section 10.15.4.1.2.
4.2. Breeding Season
4.2.1. Breeding Population Surveys
AEA implemented the methods described in the Study Plan, with the exception of variances
explained below (Section 4.2.1.1).
The survey team used two different survey approaches for breeding population surveys in the
study area, depending on the location of the water bodies being surveyed. In most of the study
area, the same lake-to-lake survey approach used for the migration surveys was used for the
breeding surveys, with no break in timing between the spring migration and breeding survey
periods. To increase survey efficiency, the survey effort was focused on lake groups where lakes
were tightly clustered (Figures 4.1-5, 4.1-6, and 4.1-7). A rectangular area (7×11 mi) was
delineated east of the upper end of the reservoir inundation zone (“transect block” in Figure 3-1)
in an area of low topographic relief with a high density of water bodies. The transect block was
sampled during breeding waterfowl population surveys using a transect sampling approach,
rather than attempting to cover all of the water bodies completely in a lake-to-lake pattern. The
survey team recorded data in 0.25-mi (400-m) strips along transect lines spaced at 1-mi intervals,
providing sample coverage of approximately 25 percent of the survey block.
Surveys for breeding waterfowl in the transect-survey block followed standard USFWS
protocols (USFWS 1987, USFWS and Canadian Wildlife Service [CWS] 1987). The survey
team arranged parallel survey lines to cover the greatest possible number of water bodies and
wetlands. The placement of the transect lines, which were oriented systematically along the long
axis of the survey block, was done before the field season, using USGS topographic maps and
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GIS. Waypoints were calculated at transect endpoints and at 1-mi intervals along each of the
seven transects and a GPS route file using those waypoints was created for navigation during the
survey.
As in the migration surveys, a Robinson R-44 helicopter was used as the survey platform for the
breeding surveys. Flight altitude was low (125–200 ft agl), with the lower altitude being used for
the transect surveys) to permit observation of birds without having to rely on binoculars,
although binoculars were used where necessary to confirm species identification. Transect
surveys were flown at a constant speed of 45 kt and lake-to-lake surveys at a speed of 20–45 kt.
During the lake-to-lake surveys, a single observer recorded data for the entire surface area of the
water bodies surveyed. In the transect surveys, each of two observers searched for waterbirds in
a 0.125-mi (~200 m) strip on each side of the aircraft, for a total strip width of 0.25 mi (~400 m)
while the pilot navigated along the transect lines using a GPS receiver. Data collection followed
standard USFWS protocols, grouping observations into five categories: (1) lone drake; (2)
flocked drakes (2–4 males in close association); (3) pair (male and female in close association);
(4) group (≥3 mixed-sex birds of the same species in close association which cannot be separated
into singles and pairs or ≥5 flocked males of the same species); and (5) nests. Data recorded for
each observation included a GPS waypoint number and the lake group, river, or transect number.
Observations were recorded on hand-held digital voice recorders for later transcription and
transfer to a digital database for final QA/QC and analysis.
The timing of the breeding waterfowl population surveys was scheduled by evaluating the
chronology of spring break-up and snow- and ice-melt in 2013, which were monitored
throughout the spring migration surveys. Breeding waterfowl population surveys typically are
flown in late May or early June, depending on location and elevation, when pairs are present on
territories but females are not yet spending time on nests. Survey timing can affect results
because the nesting phenology of dabbling ducks is generally earlier than that of most diving
ducks, and some dabbling duck species can be missed if the survey occurs too late, after the
cryptically colored females are on nests and the more brightly colored males have left the area.
To account for this variability among species-groups, two surveys were flown, spaced 10 days
apart (Table 4.1-1), to target the expected peak presence of pairs and males of dabbling ducks
and diving ducks, respectively, which differ in migratory timing. Each survey was conducted
during the same periods as the pre-nesting Harlequin Duck surveys, taking four to five days to
complete. Weather and visibility conditions during surveys were recorded to assess the quality of
data collection.
Survey data were used to calculate the estimated densities of each species of waterfowl and to
identify areas important to breeding waterfowl, following standard protocols (USFWS and CWS
1987, Smith 1995) to convert raw survey counts to indicated total population indices. Species-
specific correction factors (when available) were applied to the indices to derive population
estimates of each species detected in the transect-survey block.
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4.2.1.1. Variances
The term “breeding-pair survey” proposed in the Study Plan (RSP Section 10.15.4.2.1) was
replaced here with “breeding population survey,” which is a more inclusive survey method. The
breeding-pair survey is designed to estimate the number of breeding pairs in an area based on
counts of single drakes and pairs of waterfowl, whereas the breeding population survey is
designed to estimate not only the number of breeding pairs in an area but also includes grouped
birds to derive a breeding population estimate for the area. The term “breeding population
survey” accurately describes the results reported in this document on breeding waterfowl
densities and population indices in the study area. Hence, more information was gathered than
was described in the Study Plan, meeting Study Plan objectives.
4.2.2. Harlequin Duck Surveys
AEA implemented the methods described in the Study Plan, with the exception of variances
explained below (Section 4.2.2.1).
In inland areas of Alaska, Harlequin Ducks predominantly forage in mountain streams and nest
in adjacent shoreline habitats. Male Harlequin Ducks are only present on breeding streams
during a short period in spring while courting females. Accordingly, pre-nesting surveys must be
conducted in that short timing window to quantify the number of nesting pairs occupying a
stream. After hatching, successful females are visible on streams with their broods, and failed
breeders often group together.
All rivers and streams flowing through the study area buffer were surveyed for breeding
Harlequin Ducks. These stream surveys extended outside the 3-mi study-area buffer where
necessary to include suitable habitats farther upstream. The survey team flew surveys for pre-
nesting and brood-rearing Harlequin Ducks in a Robinson R-44 helicopter, using two observers
seated on the same side of the aircraft. Surveys proceeded in both upriver and downriver
directions, with the helicopter positioned over one bank to provide an unobstructed view of the
entire width of the water course. Survey altitude was 100–150 ft agl and survey speed was 20–35
kt. Surveys covered primary and secondary tributary streams within the 3-mi study area buffer
and extended up to 10 mi beyond the buffer to include contiguous suitable nesting habitat
(Figures 4.1-5, 4.1-6, and 4.1-7). The extent of suitable nesting habitat was assessed initially
during the last migration survey before the first Harlequin Duck pre-nesting survey and was
continually reassessed on each Harlequin Duck survey. Observers recorded sex of individuals,
counts of adults, and counts of young on hand-held digital recorders and marked GPS waypoints
for later transcription and transfer to a digital database for analysis. Data were summarized as the
number of pairs, males, females, and young and identified streams used by breeding Harlequin
Ducks.
To account for variability in the occurrence of peak numbers of breeding pairs and brood-rearing
females on a stream, the survey team flew two pre-nesting surveys and two brood-rearing
surveys, with 10 days intervening between each pair of surveys (Table 4.1-1). The survey timing
was adjusted to the environmental conditions and breeding phenology observed in 2013.
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4.2.2.1. Variances
Although the extent of suitable nesting habitat extended >10 mi beyond the 3-mi study area
buffer on some of the major tributaries of the Susitna River, it was not logistically feasible to
follow the entire length of tributary streams as was proposed in the Study Plan (RSP Section
10.15.4.2.2). For tributaries that had suitable habitat well beyond the 3-mi study area buffer, a
survey end point was established at 10 mi beyond the buffer. That distance was based on the
linear home range of Harlequin Ducks during the pre-nesting and brood-rearing periods
(Robertson and Goudie 1999). Calculation of linear densities of Harlequin Ducks along breeding
streams was not feasible in 2013 because of differences in the upstream extent covered among
different surveys. Additional GIS analysis in the next study season should permit calculation of
linear densities. However, the same logistical constraints will persist during the next study
season. Because the surveys flown in 2013 extended beyond the outer boundary of the study area
by a distance equal to the reported linear home range of Harlequin Ducks, the variance is
consistent with study objectives.
4.2.3. Brood Surveys
AEA implemented the methods described in the Study Plan, with no variances.
Brood surveys covered the subset of water bodies within a 1-mi buffer around the locations and
alignments of proposed Project infrastructure, including access road and transmission corridors
(Figures 4.1-1, 4.1-2, and 4.1-3). The survey team examined suitable lakes, ponds, streams, and
flooded wetland complexes to provide information on waterbirds breeding in specific areas that
may be affected by Project infrastructure or activities. Two observers conducted the brood
surveys in a Robinson R-44 helicopter, flying at 125–200 ft agl and a speed of 20–45 kt. The first
survey was conducted on July 20–22, and the second was conducted two weeks later, on August
1–5, to record the presence of adults accompanied by broods of juveniles (Table 4.1-1). . In RSP
Section 10.15.4.2.3, a third brood survey was listed as a possibility, contingent on an assessment
of the developmental stages of the juvenile waterbirds observed during the second brood survey.
In 2013, the study team concluded that the first and second brood surveys were suitably timed to
cover the variability in the development of waterbird juveniles, so a third brood survey was not
needed.
The survey team circumnavigated water bodies to search for waterbird broods, recording
observations of the number of adults and young on hand-held digital recorders and as GPS
waypoints for later transcription and transfer to a digital database. Ages of waterfowl broods
(primarily ducks) were estimated by classifying each brood into one of seven age classes, based
on chick plumage patterns (Bellrose 1976). Data were summarized by species, location, survey
area, and brood age class. Nest-initiation dates were estimated by subtracting the average
incubation period from the estimated age of young.
4.2.3.1. Variances
No variances from the methods described in the Study Plan were necessary during the 2013
study season.
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4.3. Information for Mercury Study
AEA implemented the methods described in the Study Plan, with the exception of variances
explained below (Section 4.3.1).
Scientific literature was reviewed to compile and synthesize information on the food habits and
diets of piscivorous waterbirds in freshwater aquatic systems, in support of the Mercury
Assessment and Potential for Bioaccumulation Study (Study 5.7). Review of this information
was recommended by USFWS in comments on the PAD for the Project (letter from USFWS to
AEA dated May 31, 2012).
When nests of obligate piscivorous waterbirds (e.g., loons, grebes, terns) were observed during
the breeding aerial surveys, the locations were recorded as GPS waypoints and marked on field
survey maps. The locations of broods of piscivorous waterbirds also were recorded during brood
and fall migration surveys. No nests of piscivorous waterbirds were examined on the ground.
Only one nest was found but, because it was located on Cook Inlet Regional Working Group
(CIRWG) lands, it could not be visited.
4.3.1. Variances
The study objective for acquiring tissue samples of piscivorous waterbirds for laboratory analysis
of mercury levels was based on opportunistically finding nests during breeding aerial surveys
and visiting those nests after the nesting season to collect feather samples, as described in RSP
Section 10.15.4.3. Fewer nests of piscivorous waterbirds were found than expected during
breeding aerial surveys in 2013. Only one Common Loon nest was found and no nests of other
piscivorous waterbirds were found in 2013. Lack of access to CIRWG lands prevented a visit to
look for feather samples at the Common Loon nest. However, that nest was located on an island
in the Fog Lakes area and whether a helicopter could have landed there safely was questionable.
Broods of all piscivorous waterbirds were found in the waterbird study area and lakes where they
were observed can be targeted during future surveys for nesting birds.
As an ancillary method to attempt to obtain feathers of piscivorous waterbirds, the Study Plan
proposed to supplement the collection of feathers from waterbird nests by visiting nest sites of
Peregrine Falcons located in or near the study area and collecting feathers and prey remains of
waterbirds eaten by the falcons. Peregrine Falcons are predators of a variety of birds, including
waterbirds, and examination of prey remains is a commonly used technique to investigate their
food habits, although the likelihood of obtaining feathers specifically from piscivorous species of
waterbirds is unknown and probably small. Although the study team possessed the required
federal salvage permit to collect feathers from all species of migratory birds except eagles, falcon
nests were not visited in 2013 because a permit was not obtained for salvage of eagle feathers
(see ISR Study 10.14, Surveys of Eagles and Other Raptors for more details), so the planned
sampling visit was postponed until the second study season.
Further discussion with USFWS is planned in 2014 to discuss all possible methods of tissue
collection, including feathers, feces, eggshell fragments, and eggshell swabbing, for effective
laboratory analysis of mercury levels in piscivorous waterbirds. The effectiveness of determining
mercury levels from these different kinds of tissue samples will be discussed and evaluated.
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5. RESULTS
Data developed in support of ISR 10.15, Waterbird Migration, Breeding, and Habitat Use, are
available for download at http://gis.suhydro.org/reports/isr. The data are in the following files:
• ISR_10_15_WBRD_Data_ABR.gdb/ISR_10_15_WBRD_Breeding_Transect_Lines
• ISR_10_15_WBRD_Data_ABR.gdb/ISR_10_15_WBRD_Breeding_Lake_Groups
• ISR_10_15_WBRD_Data_ABR.gdb/ISR_10_15_WBRD_Migration_Lake_Groups
• ISR_10_15_WBRD_Data_ABR.gdb/ISR_10_15_WBRD_Lakes_in_Breeding_Groups
• ISR_10_15_WBRD_Data_ABR.gdb/ISR_10_15_WBRD_Lakes_in_Migration_Groups
• ISR_10_15_WBRD_Data_ABR.gdb/ISR_10_15_WBRD_Lakes_Brood_Survey
• ISR_10_15_WBRD_Data_ABR.gdb/ISR_10_15_WBRD_HarlequinDuck_Streams
• ISR_10_15_WBRD_Data_ABR.gdb/ISR_10_15_WBRD_Migration_Streams
• ISR_10_15_WBRD_Data_ABR.gdb/ISR_10_15_WBRD_Spring_Visuals
• ISR_10_15_WBRD_Data_ABR.gdb/ISR_10_15_WBRD_Fall_Visuals
• ISR_10_15_WBRD_Breeding_Lake_2013.xlsx
• ISR_10_15_WBRD_Breeding_Transect_2013.xlsx
• ISR_10_15_WBRD_Brood_Survey_2013.xlsx
• ISR_10_15_WBRD_Harlequin_Breeding_2013.xlsx
• ISR_10_15_WBRD_Spring_Migration_2013.xlsx
• ISR_10_15_WBRD_Fall_Migration_2013.xlsx
• ISR_10_15_WBRD_NoctVisual2013.xlsx
• ISR_10_15_WBRD_Radar2013.xlsx
• ISR_10_15_WBRD_Visuals2013.xlsx.
5.1. Spring and Fall Migration
Thirty-eight species of waterbirds were observed during migration, breeding, and brood-rearing
surveys in the waterbird study area (Table 5.1-1). Representatives from nine species or species-
groups were recorded: geese (three species), swans (two species), ducks (21 species), loons (four
species), grebes (two species), Sandhill Crane, gulls (three species), Arctic Tern, and Long-tailed
Jaeger. Although shorebirds frequently are included in the general category of waterbirds, that
broad species-group was included in a separate study (Study 10.16, Landbirds and Shorebirds),
for which the results from 2013 are reported in ISR Study 10.16.
Twenty-seven species of waterbirds were confirmed as breeders in the study area, based on the
presence of a nest or brood recorded during surveys. Another three species are possible breeders
because they were observed in the study area during the breeding season and the area is within
their breeding range. Eight other species observed only during spring and fall were considered
migrants in the study area.
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5.1.1. Aerial Surveys
5.1.1.1. Spring Migration
5.1.1.1.1. Temporal and Spatial Patterns
During spring, the timing of the arrival of waterbirds and their distribution in the study area was
dependent on the availability of open water and suitable staging habitats. During the first three
migration surveys (April 23, 29, and May 5), the only open water found on water bodies were at
some beaver ponds adjacent to Indian River and at the outlets of a few large lakes, including
Clarence, Deadman, Murder, and Stephan lakes. Small numbers of waterbirds (2–20 birds) were
observed staging at each of these water bodies, with the beaver ponds adjacent to Indian River
supporting the highest number of waterbirds on each of the three surveys (Table 5.1-2). Five
species of waterbirds were recorded on these water bodies during one or more of these three
surveys: Trumpeter Swan, Mallard, Bufflehead, goldeneyes, and Common Merganser (Table
5.1-3).
On April 23 and 29, streams were mostly frozen; small open-water areas were present on the
Nenana and Susitna rivers where leads had formed and on a few tributaries where snow cover
had caved into drainages. Small stretches of open water also were found on a few streams (i.e.,
Fog Creek and the stream connecting Stephan and Murder lakes) where it is likely that a spring
was creating open water. On April 23, four waterbirds (a pair each of Trumpeter Swans and
Mallards) were found at the stream connecting Stephan and Murder lakes and eight waterbirds,
consisting of six Trumpeter Swans and two Mallards, were seen at that same location on April 29
(Table 5.1-2). The only other waterbirds observed on streams on April 29 was a flock of eight
Mallards at a lead on the Nenana River. On May 5, many streams had small sections of open
water and a total of 72 waterbirds were found occupying them. The Indian and Nenana rivers,
and the stream connecting Stephan and Murder lakes supported the highest numbers of
waterbirds on May 5. Northern Pintail, Northern Shoveler, and Mew Gull were species that were
first observed in the study area on May 5 and all three species were staging along streams (Table
5.1-3). Seven waterbirds, consisting of two Mallards, two Buffleheads, one goldeneye, and two
Mew Gulls, were observed staging on the Susitna River on May 5 at open-water leads between
the confluences of Indian River and Fog Creek (Table 5.1-2). The numbers of waterbirds staging
on water bodies and streams were similar on April 23 and 29, but by May 5, waterbirds were
found mostly on streams (69 percent) rather than water bodies (31 percent). Most waterbirds in
the study area on May 5 were found in the Chulitna and Gold Creek corridor survey areas,
followed by the Denali Corridor and Watana Reservoir survey areas.
On May 11 and 18–19, large, deep lakes remained about 98 percent ice-covered with open water
continuing to be found only at inlet and outlet areas. Lakes (Clarence, Deadman, Murder, and
Stephan lakes) that were occupied by waterbirds on earlier surveys at these small open-water
areas were occupied with a greater number of waterbirds on May 11 and 18–19 (Figure 5.1-1,
Table 5.1-2). Waterbirds also were found at other large lakes (Pistol Lake and large lakes just
north of Stephan Lake) where open water had formed since May 5 (Figure 5.1-1, Table 5.1-2).
The highest number of waterbirds recorded at one of these large lakes was 84 birds at Murder
Lake on May 11and 72 birds at Stephan Lake on May 18–19. Waterbirds also occupied some
shallow water bodies that were partially to completely thawed on May 11 and May 18–19,
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including a couple of water bodies in the Fog Lakes group and Lake 1294 along the Denali
Highway just northeast of Drashner Lake. From 200 to 250 waterbirds, including geese, swans,
ducks, and gulls, occupied Lake 1294 on both May 11 and May 18–19.
Similar to the survey on May 5, most waterbirds (>60 percent) were found on streams on May 11
and May 18–19 rather than on water bodies (Table 5.1-2). The amount of open water on streams
continued to increase considerably with each successive survey, and by May 18–19, stretches of
open-water were common on the Susitna and Nenana rivers and their tributaries. On May 11,
469 of the 1,022 waterbirds (46 percent) counted in the study area were observed staging on the
Susitna River. A similar number of those birds on the Susitna River were observed in the Gold
Creek Corridor survey area (i.e., from the railroad bridge crossing at Project River Mile (PRM)
140.0 to the proposed dam site at PRM 187.1) and in the Watana Reservoir survey area (i.e.,
from the proposed dam site to above the Oshetna River confluence at PRM 237.7; Table 5.1-2).
By May 18–19, 634 waterbirds, representing 52 percent of all waterbirds recorded in the study
area on those dates, staged at open-water leads on the Susitna River. Most (60 percent) of the
waterbirds on the Susitna River on May 18–19 were found above the proposed dam site in the
Watana Reservoir survey area (Table 5.1-2). The portion of the Nenana River within the study
area supported 109 waterbirds on May 11 and 117 waterbirds on May 18–19. Fifteen species of
waterbirds were observed staging on the Susitna River on May 18–19 and 11 species were
staging on the Nenana River. Open-water areas at the confluence of tributaries with the Nenana
and Susitna rivers were popular staging sites. Six waterbird species were observed in the study
area for the first time on May 11: Canada Goose, Bonaparte’s Gull, and four species of ducks,
including the first sighting of Harlequin Ducks on the Susitna River (Table 5.1-3). Another four
species of ducks (scaup, Red-breasted Merganser, Redhead, and Canvasback) arrived in the
study area by May 18–19.
By May 23–24, open water was present on many small water bodies <3,000 ft elevation and
along the shorelines of some of the larger lakes. The amount of open water at inlet and outlet
areas on large lakes (e.g., Clarence, Deadman, Pistol, Murder, and Stephan lakes) had increased
since May 18 but overall these lakes and other large lakes were still 95 percent ice-covered.
Waterbirds were crowded into these small open-water areas on large lakes and also were
observed throughout the study area on some of the smaller water bodies with open water (Figure
5.1-1, Table 5.1-2). The highest concentrations of waterbirds staging on lakes were at Murder,
Stephan, and Pistol lakes, and at water bodies along the Denali Highway and in the Fog Lakes
group.
Sections of some streams within the study area were mostly ice-free and flowing fast on May
23–24 (Indian and Oshetna rivers, and Portage, Fog, and Watana creeks), including the section of
the Susitna River between Jay Creek and the Oshetna River. Other streams were still mostly
snow-covered, while meltwater runoff was flowing on top of snow and ice in Deadman, Devil,
and Goose creeks. It is likely that the increase in the availability of open water on lakes and the
increase in the volume of water flowing in streams led to the distribution of waterbirds shifting
slightly from streams to water bodies on May 23–24 compared to the previous three surveys,
however the overall number of waterbirds on streams (55 percent) was still slightly higher than
on water bodies (45 percent). Of 2,299 waterbirds recorded in the study area on May 23–24, 47
percent were found on the Susitna River, and of all waterbirds recorded on streams on that
survey, 85 percent were on the Susitna River (Table 5.1-2). Most of the waterbirds on the Susitna
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River (65 percent) on May 23–24 were found below the proposed dam site in the Gold Creek
Corridor survey area. Brushkana and Seattle creeks and the Nenana River in the Denali Corridor
survey area supported between 38 and 66 waterbirds on May 23–24. Fewer than 16 waterbirds
were observed on all other streams in the study area on that survey. Snow Goose, Herring Gull,
and Horned Grebe were newly detected species in the study area on May 23–24 (Table 5.1-3).
Warm temperatures in the study area between May 23–24 and May 28–29 resulted in rapid snow
melt, high-velocity flows in streams, and most water bodies <3,000 ft elevation having some
open water. Because of these conditions, most waterbirds (78 percent) were found on water
bodies on May 28–29 rather than on streams. Streams generally were no longer suitable for
staging on May 28–29 because of their high velocity and muddy water. For example, the number
of waterbirds recorded on the Susitna River in the Gold Creek Corridor survey area on May 28–
29 was only 44 birds compared to 702 birds on the previous survey, and the number recorded on
the Susitna River in the Watana Reservoir survey area also dropped from 374 birds on May 23–
24 to 131 birds on May 28–29 (Table 5.1-2). The total number of waterbirds in the study area
was similar on surveys conducted on May 23–24 (2,299 birds) and May 28–29 (2,090 birds), and
thus it is likely that most waterbirds that had been staging on streams on May 23–24 shifted to
staging on water bodies and tributaries of the Susitna River on May 28–29 rather than leaving the
study area.
For most lakes and other water bodies in the study area, the highest number of waterbirds was
observed on May 28–29 (Figure 5.1-1). More waterbirds were counted on large lakes, like
Clarence, Murder, and Stephan lakes, on May 28–29 than on any previous spring survey, with
numbers on each lake ranging from 108–144 birds (Table 5.1-2). The Fog Lakes group and a
group of water bodies near Goose Creek and the Oshetna River also supported hundreds of
waterbirds. Lake 1294 along the Denali Highway just northeast of Drashner Lake had fewer
waterbirds on May 28–29 (175 birds) than any of the previous three surveys, however the
number of waterbirds on nearby water bodies doubled from the number on May 23–24 because
of the availability of open water. Many waterbirds, particularly American Wigeon, Mallard,
Northern Shoveler, Northern Pintail, scaup, and Harlequin Duck, were commonly seen in single
species-groups of 10–30 birds and occasionally in groups from 31–100 birds. Seven species not
previously recorded in the study area during spring 2013 were seen on May 28–29, including
Long-tailed Duck, two species of scoters, three species of loons, and Red-necked Grebe (Table
5.1-3). Five additional species (Greater White-fronted Goose, Gadwall, Black Scoter, Pacific
Loon, and Arctic Tern) of waterbirds were not detected during migration surveys, and were seen
on the first breeding survey on June 1–5.
During the two migration surveys in April, waterbirds were found only in the Denali, Chulitna,
and Gold Creek corridor survey areas, with most birds (54 percent) occurring in the Chulitna
Corridor (Table 5.1-2). For each survey in May, the Chulitna Corridor survey area had the lowest
number of waterbirds recorded among all the survey areas except for the Dam/Camp Area,
where no waterbirds were observed until May 28–29 (Figure 5.1-1). The highest number of
waterbirds recorded among the Watana Reservoir and Denali and Gold Creek corridor survey
areas during each survey in May differed from survey to survey. Most waterbirds were recorded
in the Gold Creek Corridor survey area on May 5 and May 23–24, while on May 11 most
waterbirds were found in the Denali Corridor survey area (Table 5.1-2). On May 18–19 and 28–
29, most waterbirds were recorded in the Watana Reservoir survey area. For four of the five
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survey areas, the highest number of waterbirds recorded within the survey area during spring
occurred on May 28–29: 817 birds in the Watana Reservoir, 727 birds in the Denali Corridor, 90
birds in the Chulitna Corridor, and 22 birds in the Dam/Camp Area. The Gold Creek Corridor
survey area had more birds on May 23–24 (919 birds) than on May 28–29 (427), largely because
of the drop in the number of waterbirds on the Susitna River.
5.1.1.1.2. Taxonomic Patterns
Trumpeter Swans were one of the first species to arrive in the study area during spring 2013 and
a pair of birds often occupied small open-water outlet areas of large lakes (Tables 5.1-3 and 5.1-
4). Pairs of swans were recorded at the same sites for at least four consecutive spring surveys.
Swans were also observed staging along streams, including the Indian, Nenana, and Susitna
rivers, Brushkana and Deadman creeks, and the stream connection between Stephan and Murder
lakes. Numbers of swans observed in the study area continued to increase with each spring
survey and most birds were observed as pairs or in groups of less than ten birds (Table 5.1-4).
The highest number of swans recorded in the study area during spring was 72 birds on May 23–
24, almost half of which were in the Denali Corridor survey area (Appendix B). During late
April, swans were only found in the Denali and Gold Creek corridor survey areas, with most
birds occurring in the Gold Creek Corridor (Table 5.1-4). On every spring migration survey in
May, most of the swans in the study area were observed in the Denali Corridor survey area
(range 13–35 swans), followed by the Watana Reservoir and the Gold Creek and Chulitna
corridor survey areas. No swans were recorded in the Dam/Camp Area during spring.
Most swans recorded in the study area during spring were probably local breeders and were
staging at sites near nesting territories. Four nests were found in the study area during migration
or breeding surveys, three in the Denali Corridor survey area and one in the Chulitna Corridor
survey area. The long, cold spring in 2013 may have caused some swans to forego nesting or
may have contributed to early nest failures.
Three species of geese were recorded in small numbers in the study area during spring, with the
first observations occurring on May 11 in the Watana Reservoir and Denali Corridor survey
areas (Table 5.1-4, Appendix B). Canada Geese were observed in flocks of no higher than 10
birds on May 11 and most were seen staging along leads in the Nenana River and in the lower
section of Seattle Creek in the Denali Corridor survey area (Appendix B). A few Canada Geese
were recorded in the Gold Creek Corridor survey area on May 18–19 and 23–24 on the Susitna
River and at Murder Lake, respectively. Two flocks of Snow Geese were observed in flight
during migration surveys near the Oshetna River in the Watana Reservoir survey area: a group of
80 Snow Geese on May 23–24, and a group of 10 geese on May 28–29 (Table 5.1-3). Snow
Geese were not observed staging on lakes during any spring migration survey but a few birds
were seen on lakes during the June 1–5 breeding survey in the Watana Reservoir survey area.
Greater White-fronted Geese were not observed during spring surveys, and only three birds were
observed during breeding and fall migration surveys. No goose broods were seen during brood-
rearing surveys and that coupled with the low numbers of geese seen during spring probably
indicates that most geese observed in the study area are migrants or non-breeders. Of all
observations of geese staging in the study area during spring migration, most were observed in
the Denali Corridor survey area, followed by the Gold Creek Corridor and Watana Reservoir
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survey areas (Table 5.1-4). No geese were recorded in the Chulitna Corridor survey area or the
Dam/Camp Area during spring.
Ducks were the most abundant waterbird species-group in the study area and were represented
by 21 species (Tables 5.1-1 and 5.1-4; Appendix B). Some species arrived early in the study area
and were present in small numbers during late April, including Mallard, goldeneyes, Common
Merganser, and Bufflehead (Table 5.1-3). Six more species, including four dabbling ducks and 2
diving ducks, arrived in early May, and four more diving ducks arrived by mid-May. Long-tailed
Ducks and two species of scoters were first seen in the study area in late May. Peak numbers
were counted for eight species of ducks on May 23–24 (American Wigeon, Northern Shoveler,
Northern Pintail, Green-winged Teal, Harlequin Duck, Bufflehead, goldeneyes, and Red-
breasted Merganser) and for five species on May 28–29 (Ring-necked Duck, scaup, Surf Scoter,
White-winged Scoter, and Long-tailed Duck) (Appendix B). Numbers of Mallards and Common
Mergansers were highest on May 18–19, and small numbers of Canvasback and Redhead were
seen on that survey only. Black Scoters were not seen in the study area until the breeding survey
on June 1-5.
Most ducks in the study area were found in the Chulitna Corridor survey area in late April and
early May because of the occurrence of open-water on beaver ponds. After May 5, numbers of
ducks in the Chulitna Corridor survey area increased slowly to a maximum number of 83 ducks
recorded within the survey area during spring. The number of ducks recorded in the study area
was less than 100 birds on each of the first three migration surveys, with the highest numbers of
32 and 27 ducks occurring on May 5 in the Chulitna and Gold Creek corridor survey areas,
respectively. A dramatic increase in the number of ducks in the study area occurred on May 11,
when a total of 852 birds were counted (Table 5.1-4). During that survey, the number of ducks in
the Watana Reservoir and the Denali and Gold Creek corridor survey areas ranged from 208 to
309 birds, with the highest number occurring in the Gold Creek Corridor. Ducks continued to
increase in number in the study area on May 18–19 (1,139 ducks) and reached a peak number of
2,135 ducks on May 23–24. Most of the ducks recorded in the study area on May 18–19 were
found in the Watana Reservoir survey area (37 percent) and on May 23–24, most ducks were
observed in the Gold Creek Corridor survey area (41 percent). Most of the ducks in the two
survey areas on those surveys occurred on the Susitna River (Table 5.1-2). The total number of
ducks in the study area on May 28–29 (1,961 ducks) was slightly less than the previous survey,
and most ducks were found in the Watana Reservoir survey area (40 percent). Hundreds of ducks
(from 208 to 885 ducks) were found on each survey from May 11 to May 28–29 in each of three
survey areas: the Watana Reservoir and the Denali and Gold Creek corridors survey areas. No
ducks were recorded in the Dam/Camp survey area until May 28–29 when 29 were recorded on
Tsusena Creek and some of the small water bodies (Tables 5.1-2 and 5.1-3).
Red-throated, Common, and Yellow-billed loons were observed in the study area on May 28–29
and Pacific Loons were first seen during the June 1–5 breeding survey (Table 5.1-3). A total of
12 loons were observed in the study area on May 28–29 (Table 5.1-4). Six of those 12 loons
were recorded in the Denali Corridor survey area and included sightings of all three of the
species recorded on that day (Appendix B). A total of five loons, including three Red-throated
Loons and two Common Loons, were recorded in the Gold Creek Corridor survey area and one
Red-throated Loon was found in the Watana Reservoir survey area. Most loons that were
breeders in the study area probably did not arrive until early June because many of their breeding
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lakes were inaccessible in late May. Red-throated, Pacific, and Common loons are breeders in
the study area, whereas the Yellow-billed Loon is a casual or rare migrant in the area.
Horned Grebes arrived in the study area by May 23–24 and Red-necked Grebes by May 28–29
(Table 5.1-3). A total of six grebes were observed in the study area on May 23–24 and five
grebes on May 28–29 (Table 5.1-4). Grebes were recorded in all of the survey areas during
spring except the Dam/Camp Area. The highest number of grebes occurred in the Watana
Reservoir survey area on May 23–24 when five Horned Grebes were observed (Table 5.1-4,
Appendix B). Two sightings of grebes were recorded in the Denali Corridor survey area and one
each in the Chulitna and Gold Creek Corridor survey areas.
Three species of gulls were recorded in the study area during spring (Table 5.1-1). The first
sighting of two Mew Gulls occurred on May 5, with the peak number occurring on May 11(109
birds; Table 5.1-3). Small numbers of Bonaparte’s Gulls were seen on surveys on May 11, 23–
24, and 28–29 and Herring Gulls were observed on the last two migration surveys (Appendix B).
Arctic Terns were not seen in the study area until the June 1–5 breeding survey. All four species
breed in small numbers in the study area. The highest number of gulls recorded during a spring
migration survey occurred on May 11 when 112 birds were recorded (Table 5.1-4). All sightings
of gulls on that date occurred in the Watana Reservoir and Denali and Gold Creek corridor
survey areas and the numbers in each survey area ranged from 33 to 44 birds, with the highest
number occurring in the Watana Reservoir survey area. The highest number of gulls recorded
among those three survey areas on subsequent spring surveys differed from survey to survey: 6
gulls were recorded in both the Denali and Gold Creek corridors on May 18–19, 29 gulls in the
Watana Reservoir on May 23–24, and 25 gulls in the Denali Corridor on May 28–29. Gulls were
recorded in the Chulitna Corridor survey area only on May 28–29 when three Mew Gulls were
observed. No gulls were recorded in the Dam/Camp Area during spring.
5.1.1.2. Fall Migration
5.1.1.2.1. Temporal and Spatial Patterns
Maximal numbers of waterbirds were recorded during the first fall migration survey, August 14–
18 (2,963 birds; Table 5.1-4). Numbers varied thereafter between about 2,200 and 2,800 birds
with no apparent trends until the third week of September, when totals dropped to about 1,450–
1,600 birds. Numbers again remained steady until the second week of October when totals
dropped to fewer than 600 birds. Broods from all species groups were observed during migration
surveys in August, and small groups of birds and individuals were located on water bodies of
various sizes throughout the study area. To some extent, subsequent changes in local numbers
during the fall likely represented movements of local breeding birds within the study area.
Stephan and Murder lakes, in the Gold Creek Corridor survey area, were two of the most heavily
used lakes during fall migration (Figure 5.1-2). Murder Lake is relatively small and shallow with
emergent vegetation, and is especially favored by dabbling ducks and swans. Stephan Lake is
large and deep, with shallow margins, particularly near the inlet and outlet streams. It supported
both dabbling and diving ducks, loons, grebes and swans. Also consistently used were Clarence
Lake and the southernmost Fog Lake (WB 059 in the APA study) in the Watana Reservoir
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survey area. Like Stephan Lake, these large, deep lakes supported both large numbers of birds
and a wide range of species.
In the Denali Corridor survey area, large numbers of waterbirds were found throughout the fall in
a series of shallow unnamed water bodies connected to Brushkana Creek, and to a lesser extent
in the interconnected unnamed ponds and discrete small lakes east of Cantwell (Figure 5.1-2,
Table 5.1-2). Other water bodies that supported high numbers of waterbirds at some point during
the fall included the easternmost large Fog Lake (WB 060 in the APA study), Pistol Lake,
Watana Lake, and Molar Lake in the Watana Reservoir survey area, and Big Lake and Deadman
Lake in the Denali Corridor survey area.
Parallel to the trends observed for the most abundant species, peak waterbird numbers (i.e., all
species combined) occurred between mid-August and mid-September in most survey areas
(Table 5.1-4). Ice was first observed on lakes in the study area during the September 16–18
survey, and waterbird numbers declined thereafter in the Watana Reservoir, Denali Corridor and
Chulitna Corridor survey areas. In contrast, waterbird numbers increased in the Gold Creek
Corridor survey area in late September and peaked in early October, largely due to increased use
of Stephan and Murder lakes which remained ice-free. The amount of ice cover in the study area
was variable through early October, but had increased substantially by October 10, after which
numbers declined steeply in all areas. Most birds after this date were recorded in the Gold Creek
Corridor survey area.
Cumulative numbers of ducks (i.e., all duck species across all fall surveys) were highest in the
Denali Corridor survey area. This area contained the highest number of ducks through mid-
September, followed by the Watana Reservoir survey area (Table 5.1-4). After mid-September,
the highest numbers of ducks occurred in the Gold Creek Corridor survey area, followed by the
Watana Reservoir survey area.
Cumulative fall swan numbers were very similar between the Gold Creek and Denali Corridor
survey areas. The Denali Corridor survey area contained the highest number of swans through
mid-September, followed by the Gold Creek survey area (Table 5.1-4). Relative use of the two
areas switched after mid-September, when swan numbers in the Denali Corridor dropped
slightly, but numbers in the Gold Creek Corridor increased with the arrival of groups,
particularly on Murder and Stephan lakes.
Cumulative fall loon numbers were highest in the Gold Creek Corridor survey area, primarily
due to large numbers in August. Throughout the fall, however, numbers were highest during at
least one survey in each of three other survey areas (Watana Reservoir, Chulitna Corridor, and
Denali Corridor). Cumulative grebe numbers were highest in the Watana Reservoir survey area,
followed by the Gold Creek survey area (Table 5.1-4).
5.1.1.2.2. Taxonomic Patterns
Trumpeter Swan counts were steady through mid-September and swans were found mostly in
pairs (with or without cygnets) and in small groups (Table 5.1-3, Appendix B). Swan numbers
increased between mid-September and early October as larger flocks (containing up to 76
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Trumpeter and unidentified swans) began to arrive, primarily on Murder and Stephan lakes
(Tables 5.1-2 and 5.1-4).
Scaup were by far the most numerous ducks observed during fall surveys (Table 5.1-3). Counts
were variable (possibly related to survey conditions) but showed no overall trend until early
September, after which they declined steadily until the end of the season. Similar patterns were
observed for several dabbling duck species, including American Wigeon, Northern Pintail,
Green-winged Teal and Northern Shoveler, all of which peaked between mid-August and mid-
September (Table 5.1-3, Appendix B). In contrast, Mallard numbers varied through the third
week of September before peaking in early October.
Patterns were weak for scoters and mergansers, but both groups reached maximal numbers in
late August and declined a bit thereafter (Table 5.1-3, Appendix B). The highest count of Surf
Scoters occurred in late August and a small pulse of Black Scoters was recorded in the second
week of October.
Goldeneye and Bufflehead numbers were level throughout the season, except for a pulse of
goldeneyes in early October (Table 5.1-3, Appendix B). The highest count of Long-tailed Ducks
occurred during the first fall migration survey in August, after which they steadily declined until
the end of the season. No Long-tailed Ducks were observed after the October 4–6 survey. Loons
and grebes were present throughout the fall season, but their numbers declined after the second
week of September.
5.1.1.3. Relative Importance Values of Lakes
Relative importance values were calculated for 34 lakes (or lake groups) used by waterbirds
during fall 1980 and spring 1981 by Kessel et al. (1982). In 2013, information on the mean
number of birds, density, and species richness (see Table 5.1-5) on 25 of those lakes was used to
calculate relative importance values for both spring and fall migration, following the same
method used in the 1980s (Table 5.1-6). Based on these factors and the duration of use by
waterbirds, these 25 lakes appeared to include the majority of the most important water bodies
used during spring and fall. Exceptions include the aforementioned unnamed water bodies in the
Denali Corridor survey area (heavily used during fall especially) and river habitats (important
during spring).
Similar to the earlier study, Murder Lake ranked as the most important water body in both fall
and spring, followed by Stephan Lake (except for spring 1980 when Stephan Lake ranked third).
Murder Lake has a comparatively small surface area but contained by far the highest density of
waterbirds—especially dabbling ducks—in both fall and spring (Table 5.1-5). Although Murder
Lake is shallow, stream flow from Stephan Lake keeps the lake partially open in early spring,
which contributed to the very high importance value of Murder Lake in spring 2013, when few
other water bodies were available to migrants. Murder Lake also remained partially open late in
the fall after other shallow lakes froze and became unavailable to waterbirds.
Large, deep lakes such as Stephan, Clarence, Watana, Big, Deadman, and Fog lakes remained
open throughout the fall as well, and were more heavily used by migrants during fall than spring
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(Table 5.1-2). As described earlier, many waterbirds used river habitats during spring migration,
when most lakes were ice covered.
Stephan Lake ranked second in importance in spring and fall (Table 5.1-6). It generally had a
high number of birds and wide range of species. Diving ducks, swans, loons and grebes were
observed throughout the lake and dabbling ducks were observed primarily in the shallower
margins.
Clarence Lake ranked third in importance in spring and fourth in fall 2013 (Table 5.1-6). Scaup
were the most numerous species in both seasons, but the lake also was used during both spring
and fall by other diving ducks, dabbling ducks and swans (Table 5.1-2). The range of species
was greater in the fall, and included grebes and Common Loon.
Pistol Lake ranked fourth in importance in spring 2013. A group of nine Trumpeter Swans was
observed on May 11, but the lake was otherwise unoccupied until the fourth week of May when
small numbers of several species of diving and dabbling ducks and a flock of 36 scaup were
observed. The lake ranked only eleventh in importance in the fall, primarily because of low
overall numbers and density, but it was used regularly by several species of diving and dabbling
ducks until the last two fall surveys, when no birds were present despite an abundance of open
water.
The southernmost Fog Lake (WB 059) ranked fifth in spring and third in fall 2013 (Table 5.1-6).
Scaup were the most numerous species group in both seasons, but the lake was also used during
both spring and fall by other diving ducks and dabbling ducks (Table 5.1-2). Grebes, swans and
Common Loon used the lake during fall.
Also of high apparent importance were the series of unnamed ponds connected to Brushkana
Creek in the Denali Corridor and, secondarily, the unnamed water bodies east of Cantwell
(Figure 5.1-2, Table 5.1-2). The relatively small, shallow water bodies connected to Brushkana
Creek were consistently used by very high numbers of birds (Table 5.1-2) and, like Murder Lake,
were kept open by stream flow after other shallow ponds in the area had frozen. At a higher
elevation than Murder Lake, these ponds were not available as early in the spring or as late in the
fall, but they supported high densities of birds through the second week of October. Accurate
surface area measurements are not yet available for these water bodies, and they were not
included in importance value analyses conducted in the 1980s or in 2013.
5.1.2. Ground-based Surveys
5.1.2.1. Spring Migration
The sampling effort in spring 2013 comprised 87.5 h during 122 diurnal radar sessions across 43
days, 183.6 h during 267 nocturnal radar sessions across 42 nights, and 651.4 h during 1,558
diurnal visual survey sessions across 45 days. Audiovisual survey (night-vision) sessions
conducted concurrently with the first 2–3 h of nocturnal radar sampling totaled 80.6 h across 43
nights. Radar and nocturnal visual sampling efforts were reduced on 10 days and 14 nights,
respectively, because of precipitation, logistical problems, and contamination by insect targets.
Precipitation prevented all sampling on two days and three nights. No diurnal data were collected
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during 19 visual survey sessions (1.2 percent of total) on four days because of logistical issues
during crew transitions, a rain storm, and technical problems.
5.1.2.1.1. Radar Surveys
5.1.2.1.1.1. Passage Rate
During spring, both diurnal and nocturnal radar passage rates remained low until May 9, with
higher rates occurring afterward until May 30 (Figure 5.1-3). Mean passage rates across the
spring season varied among periods of the day and night (ANOVA, F5, 157 = 4.86, P < 0.001;
Figure 5.1-4) and were highest during nocturnal hours (mean± SE = 114.4 ± 20.1 birds/km/h),
and lowest during late afternoon (19.2 ± 7.3 birds/km/h). Throughout the season, passage rates
were lower during diurnal sessions than the subsequent nocturnal sessions, regardless of the time
of day of the diurnal sampling (paired t-tests; all P < 0.03), reflecting the greater volume of
nocturnal passerine migration.
The overall mean diurnal passage rate during spring was 31.2 ± 7.8 targets/km/h (n = 42 days).
Mean daily diurnal passage rates ranged from 0 targets/km/h (morning of May 2) to 287.3 ± 9.3
targets/km/h (morning of May 21; Figure 5.1-3). Mean passage rates of diurnal targets differed
significantly among sampling periods (ANOVA, F2, 93 = 4.18, P = 0.018), being higher in the
morning than in midday or afternoon (Figure 5.1-4).
The mean nocturnal passage rate during spring migration was 98.9 ± 17.0 targets/km/h (n = 42
nights). Mean nocturnal passage rates ranged from 0.3 ± 0.2 targets/km/h on the night of April
23 to 379.6 ± 135.7 targets/km/h on May 16 (Figure 5.1-3). The mean passage rate of the
nocturnal targets tended to increase for the first 4 h after sunset, with rates more than 1 h after
sunset significantly higher than during the crepuscular period in the first hour after sunset
(ANOVA, F2, 117 = 5.51, P = 0.005; Figure 5.1-5). The rapidly shortening nocturnal period as the
spring progressed precluded analysis of nocturnal hours more than 4 h after sunset.
5.1.2.1.1.2. Flight Direction and Distribution of Targets
In the spring, flight directions of the majority of targets during both diurnal (66.3 percent) and
nocturnal (75.6 percent) survey periods were westerly (between 225° and 315°; Figure 5.1-6).
Mean spring flight directions were 255° (median = 260°; CSD = 64°; r = 0.54) for diurnal targets
and 268° (median = 270°; CSD = 54°; r = 0.65) for nocturnal targets.
Targets were categorized by whether north or south transects were crossed or would have been
crossed by extrapolation of flight paths. Daily mean passage rates for diurnal targets crossing
north (28.5 ±7.8 targets/km/h) and south (26.7±7.1 targets/km/h) of the radar station were similar
(paired t-test, t41 = 0.62, P = 0.54). Similarly, for nocturnal targets there were no differences in
passage rates of targets crossing north (93.5± 17.0 targets/km/h) and south (88.9± 15.6
targets/km/h; paired t-test, t41 = 0.72, P = 0.48) of the station.
The effectiveness of radar sampling at the 6-km range was limited by greater frequency of
precipitation clutter and high densities of smaller targets (presumably passerines) within 1.5 km;
however, it was possible to examine temporal and spatial variation of targets sampled between
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1.5 km and 6.0 km from the radar. Numbers of targets in this range (representing flocks and
individual larger birds) showed similar diurnal and nocturnal patterns, with two distinct pulses of
increased activity: between May 5 and May 10 and from May 21 until May 29 (Figure 5.1-7).
The distribution of targets >1.5 km from the radar sampling station also corroborated results of
the spatial distribution of targets from sampling at the 1.5-km range, with approximately equal
numbers of targets observed north and south of the radar during both diurnal and nocturnal
sampling. During both diurnal and nocturnal sampling, however, the distribution of targets to the
south extended slightly further from the station than that of targets north of the station (Table
5.1-7), suggesting that migratory flight paths of larger birds (e.g., waterfowl) may be more
concentrated over the central and southern portions of the sampling area than farther (>2.5 km)
north.
5.1.2.1.1.3. Flight Altitude
The overall mean flight altitude of radar targets during diurnal sampling was 349.7 ± 8.1 m agl
(n =1,375 targets), with 22.5 percent of the targets flying at or below 100 m agl (Table 5.1-8).
The overall mean flight altitude of radar targets during nocturnal sampling was 451.3 ± 3.6 m agl
(n = 6,608 targets), with 9.0 percent of the targets flying at or below 100 m agl. Daily mean
flight altitudes were highly variable through the season during both diurnal and nocturnal
sampling periods. Mean diurnal altitudes ranged from 98 to 529 m during the study, and mean
nocturnal altitudes ranged from 174 to 576 m (Figure 5.1-8). Mean flight altitudes of radar
targets were significantly higher at night than during the day (paired t-test, t26 = –5.66, P <
0.001). Mean altitudes did not differ among periods within days (ANOVA, F2, 1,372 = 0.05, P =
0.95) or nights (ANOVA, F2, 6,605 = 1.60, P = 0.20; Figure 5.1-9).
5.1.2.1.2. Diurnal Visual Surveys
5.1.2.1.2.1. Abundance and Species Composition
Diurnal visual sampling in the spring observers recorded 8,188 birds in 2,366 flocks within the
survey area (Appendix C). The most common species group recorded during visual surveys was
passerines (excluding corvids), with 3,279 birds in 1,204 flocks (40 percent of all birds).
Common Redpoll was the most abundant of these passerines observed, with 404 birds in 100
flocks (5 percent). Waterfowl were the second most common species group (2,658 birds in 229
flocks; 32 percent); of them, 1,086 birds in 72 flocks (13 percent) were swans and at least 527
birds in 29 flocks (6 percent) were scoters. Shorebirds (1,181 birds in 188 flocks; 14 percent)
were the third most common species group, with Wilson’s Snipe the most abundant species (87
birds in 64 flocks; 1 percent). Four hundred and sixty-one diurnal raptors (eagles and hawks) in
422 flocks represented 6 percent of all birds; of them, Golden Eagles (101 birds; 1 percent) were
the most common, followed by Bald Eagles (94 birds; 1 percent).
5.1.2.1.2.2. Movement Rate
The overall mean movement rate of all birds during diurnal visual sampling was 11.30 ± 2.06
birds/h (n = 45 days). Mean movement rates on individual days ranged from 0.43 birds/h on
April 27 to 81.76 birds/h on May 17. Passerines (excluding Common Ravens) had the highest
overall mean movement rate (4.00 ± 0.95 birds/h; Table 5.1-9), with rates increasing starting
May 9 (Figure 5.1-10) and peaking with the highest rates recorded on May 17 (39.92 birds/h)
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and May 23 (13.20 birds/h). Other waterfowl (excluding swans) had the second highest overall
mean movement rate (2.31 birds/h; Table5.1-9) and peaked in abundance during the last week of
May (Figure 5.1-11) with 20.00 birds/h on May 28 and 13.31 birds/h on May 29. Shorebirds and
swans also exhibited some of the higher movement rates across the season, at 1.82 ± 0.93 birds/h
and 1.80 ± 0.71 birds/h respectively (Table5.1-9). Whimbrels were the first shorebirds observed
in the spring (May 10). Several larger flocks of other shorebird species appeared a week later,
and subsequently flocks moved through the area regularly until the last week of May (Figure 5.1-
11). Swan movements began to increase at the end of April (Figure 5.1-11) and spiked during a
week-long period in early May, when large flocks of up to 200 Tundra Swans were heard and
observed. Notably, the date with the highest number of swan detections, May 3, contributed only
64 individuals to the seasonal total, due to very limited visibility throughout the day. Of the 16
swan detections on that day, 15 were auditory-only detections, and flock sizes could not be
determined. Swan observations, primarily Trumpeter Swans when identifiable, continued
throughout the remainder of the spring season, although no flocks with more than 10 individuals
were observed after May 9.
In contrast to passerines and waterbirds, eagles (0.33 ± 0.04 birds/h) and other raptors (0.37 ±
0.05 birds/h) had comparatively moderate to low movement rates (Table 5.1-9). Eagles were
consistently present throughout the spring, whereas numbers of other raptors increased in early
May and remained high throughout the remainder of the month (Figure 5.1-12). The highest rates
for eagles occurred on May 21 (1.30 birds/h), and the highest rates for other raptors occurred on
May 9 (1.37 birds/h). Sandhill Cranes first appeared on May 9 and had low movement rates
(mean < 0.1 birds/h) throughout the subsequent weeks of the spring survey season (Figure 5.1-
13).
Within days, more passerine (ANOVA, F2, 117 = 10.78, P < 0.001) and fewer raptor movements
(ANOVA, F2, 117 = 17.44, P < 0.001) occurred during the morning than other time periods;
however within-day temporal variation in movement rates were not found among other species
groups (Figure 5.1-14).
5.1.2.1.2.3. Flight Altitude
The mean minimal flight altitude of birds observed during diurnal visual sampling was 76.7 ±
3.7 m (n = 1,064 flocks), with the highest mean minimum altitudes for loons (529.0 ± 290.6 m; n
= 5 flocks), swans (248.8 ± 38.0 m, n = 21 flocks), and eagles (204.9 ± 23.3 m; n = 51 flocks;
Figure 5.1-15). Other raptors had a lower mean minimum flight altitude (104.8 ± 14.1 m; n = 101
flocks), and the lowest mean minimum altitudes were observed in passerines (excluding ravens;
50.7 ± 2.6 m; n = 677 flocks), gulls and terns (56.6 ± 9.8 m; n = 43 flocks), and shorebirds (77.4
± 10.3 m; n = 90 flocks).
5.1.2.1.2.4. Distribution and Patterns of Movement
Observers recorded flight paths of 1,944 flocks during spring diurnal visual sampling
(Appendices D–J). Most flocks (64.13 percent of 1,132 flocks exhibiting straight-line flight) flew
in an overall westerly direction (Figure 5.1-16). Species-groups showing the strongest westerly
movement included swans (70.59 percent), other passerines (70.50 percent), other raptors (68.69
percent), shorebirds (65.22 percent), and eagles (62.69 percent). Other waterfowl (non-swans;
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47.26 percent) exhibited a bimodal pattern of movement in spring (Figure 5.1-16), as most
dabbling ducks were observed flying in a westerly direction, but many flocks of diving ducks
(particularly scoters during the last week in May ) were observed flying easterly (Appendix E).
Most flocks of birds observed at all distances had flight trajectories crossing either north or south
of the observation station (n = 1,361; Table 5.1-9, Appendices D–J). Of these, 57.8 percent
crossed south of the observation station, whereas 42.2 percent crossed to the north (Table 5.1-9).
The species groups with the highest percentages of observations south of the site were cranes (91
percent) and eagles (82 percent). Most species groups, however, exhibited similar percentages of
north versus south crossing observations (i.e., shorebirds [51.3 percent north; 48.7 percent
south], larids [50.0 percent north; 50.0 percent south], and passerines [51.1 percent north; 48.9
percent south]).
To determine if greater numbers of bird movements south of the station were due to birds
preferentially following the river channel, numbers of flight tracks crossing a 1.5-km transect
line due south of the observation station (extending the full width of the river channel at the site)
were compared with numbers crossing a 1.5-km transect line extending due north from the
observation station. Limiting the comparison to birds flying over the canyon or over the
highlands to the north, 55 percent of all birds were observed over the river channel south of the
station (Table 5.1-9). Eagles (82 percent) and cranes (86 percent) had the strongest association
with movements over the river channel relative to the highlands north of the canyon.
5.1.2.1.3. Nocturnal Audiovisual Surveys
The study team conducted crepuscular and nocturnal audiovisual observations during the first 2–
3 h post-sunset during 43 nights in the spring and recorded 183 flocks (including single
individuals), with 86 percent of detections occurring during the latter half of May (Table 5.1-10).
Waterfowl, passerines, and shorebirds composed respectively 42 percent, 30 percent, and 23
percent of flocks detected. Mean audio-visual detection rates for the season were 2.76 flocks/h
during the first hour post-sunset and 1.97 flocks/h during the second and third hour post-sunset.
Audio-only detections accounted for 23 flocks recorded, including 11 detections of Wilson’s
Snipe. Other birds detected acoustically included Swainson’s Thrush (n = 5), American Robin (n
= 2), and single detections of Tundra Swan, White-crowned Sparrow, unidentified waterfowl,
unidentified shorebird, and unidentified passerine. Among visual detections all except two flocks
were observed using binoculars. One flock of Tundra Swans at an altitude of 80 m agl and one
unidentified passerine at 5 m agl were observed with night-vision goggles. Use of night-vision
goggles was discontinued after May 19 due to increasing sky brightness at night, and binoculars
provided a greater detection range for all sampling hours. No bats were visually detected during
these crepuscular/nocturnal surveys.
5.1.2.2. Fall Migration
The sampling effort in fall 2013 comprised 94.1 h during 147 diurnal radar sessions across 54
days ; 367.4 h during 575 nocturnal radar surveys across 59 nights; and 651.6 h during 1,561
diurnal visual sessions across 61 days. Audiovisual survey (night-vision) sessions conducted
concurrently with nocturnal radar sampling totaled 94.4 h across 50 nights. Precipitation,
logistical problems, and contamination by insect targets limited radar and nocturnal audiovisual
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sampling during portions of 34 days and 45 nights and precipitation prevented sampling during
all sessions on six days and two nights. No diurnal data were collected during 23 visual survey
sessions (1.5 percent of total) on seven days, due to logistical issues.
5.1.2.2.1. Radar Surveys
5.1.2.2.1.1. Passage Rate
Fall radar passage rates were variable among different periods of the day and night (ANOVA, F5,
199 = 10.90, P < 0.001; Figure 5.1-4) and were highest during nocturnal hours mean = 118.9 ±
22.5 birds/km/h), and lowest during late afternoon (1.9 ± 0.5 birds/km/h). Passage rates tended to
be lower during diurnal radar sampling than during subsequent nocturnal sessions regardless of
the time of day of the diurnal sampling (paired t-tests; all P ≤ 0.08), although nocturnal rates
were significantly higher only for days with diurnal sampling during the mid-day period (Paired
t-test, t26 = 0.43, P = 0.02).
The overall mean fall diurnal passage rate was 10.9 ± 2.4 targets/km/h (n = 53 days). Mean
diurnal passage rates fluctuated from the start of the survey season until October 4, subsequently
remaining at very low levels through the end of the survey season (Figure 5.1-17). Mean diurnal
passage rates on individual days were highly variable and ranged from 0 targets/km/h to 110.7 ±
51.8 targets/km/h (on August 18; Figure 5.1-17). As in the spring, mean passage rates of diurnal
targets in the fall differed significantly among sampling periods (ANOVA, F2, 50 = 3.51, P =
0.04), being higher in the morning than in the late afternoon (Tukey HSD test; Figure 5.1-4).
The mean nocturnal passage rate during fall migration was 95.1 ± 17.4 targets/km/h (n = 59
nights). Overall, nocturnal migration rates were highest in late August and early September,
tapering off until late September, and subsequently remaining at very low levels through the end
of the survey season (Figure 5.1-17). Mean nocturnal passage rates on individual days ranged
from 0.4 targets/km/h on October 10 to 771.1 targets/km/h on August 23. Within a night, passage
rates were much higher during middle hours of the night than either the first hour after sunset or
the final hour before sunrise (ANOVA, F2, 149 = 17.52, P < 0.001; Tukey HD test; Figure 5.1-4)
The mean passage rates of nocturnal targets increased for the first four hours after sunset and
declined subsequently (Figure 5.1-5).
5.1.2.2.1.2. Flight Direction and Distribution of Targets
In the fall, flight directions of diurnal radar targets were not strongly oriented in any direction
and somewhat bimodal towards the east (36.5 percent between 45° and 135°) and the west (32.9
percent between 225° and 315°), while flight directions of nocturnal radar targets were generally
easterly (63.4 percent between 45° and 135°; Figure 5.1-6). Mean fall flight directions were 42°
(median = 48°; CSD = 136°; r = 0.06) for diurnal targets and 88° (median = 83°; CSD = 136°; r
= 0.45) for nocturnal targets.
Daily mean passage rates for diurnal targets crossing north (9.1 ± 2.4 targets/km/h) and south
(7.9 ± 1.8 targets/km/h) of the radar station were similar (paired t-test, t52 = 1.21, P = 2.31). For
nocturnal targets, there was a non-significant trend for more targets to cross north of the station
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(89.9 ± 17.4 targets/km/h) than to the south (85.4 ± 16.7 targets/km/h; paired t-test, t58 = 1.86, P
= 0.07).
Unlike the pattern found during spring, there were no distinct peak periods of movements for
targets >1.5 km from the 6-km-range radar during the fall survey season (Figure 5.1-7). A higher
percentage of these distant targets were observed south of the radar than to the north during
diurnal sampling, but there were no differences during nocturnal sampling (Table 5.1-7). For
example, 8 percent of daytime targets >1.5 km north of the radar were at distances of >2.5 km;
whereas 43 percent of those to the south were at distances of >2.5 km. During nocturnal
sampling, similar percentages (i.e., ~20 percent of targets) to the north and south were at
distances >2.5 km.
5.1.2.2.1.3. Flight Altitude
The overall mean flight altitude of radar targets during diurnal sampling was 240.3 ± 11.6 m agl
(n = 313 targets), with 28.1 percent of the targets flying at or below 100 m agl. The overall mean
altitude of radar targets during nocturnal sampling was 402.9 ± 3.3 m agl (n = 7,114 targets),
with 12.1 percent of the targets flying at or below 100 m agl (Table 5.1-8). Mean diurnal
altitudes ranged from 136 to 486 m during the study and mean nocturnal altitudes ranged from
237 to 681 m (Figure 5.1-18).
Mean flight altitudes of radar targets during the fall were significantly higher at night than during
the day (paired t-test, t11 = –4.58, P = 0.001). For diurnal surveys, mean flight altitudes of radar
targets were lower during mid-day hours than in the morning or late afternoon (ANOVA, F2, 310
= 3.52, P = 0.03; Figure 5.1-9). During nocturnal hours, mean flight altitudes were highest
during the hour pre-dawn and lowest during the first hour post-sunset (ANOVA, F2, 7,111 = 6.51,
P = 0.001; Figure 5.1-9).
5.1.2.2.2. Diurnal Visual Surveys
5.1.2.2.2.1. Abundance and Species Composition
During diurnal visual sampling in the fall, the study team recorded 6,445 birds in 1,234 flocks
within the study area (Appendix C). The most common species group recorded during visual
sampling was passerines (excluding ravens), with 3,793 birds in 790 flocks (59 percent of all
birds). Within this species group Common Redpoll was again the most abundant species with
1,992 birds in 231 flocks (31 percent of all birds). Sandhill Cranes were the second most
common species group (1,754 birds in 33 flocks, 27 percent of all birds). Waterfowl (372 birds
in 37 flocks; 6 percent of all birds) were the third most common species group; of them, 301
birds in 30 flocks were swans (5 percent of all birds). One hundred and seventy-one diurnal
raptors (Falconiformes) in 159 flocks represented 3 percent of total birds. Bald Eagles (37
birds;0.6 percent) were the most common raptor, followed by Peregrine Falcons (25 birds; 0.4
percent of total birds).
5.1.2.2.2.2. Movement Rate
The overall mean movement rate of all birds during diurnal sampling was 9.43 ± 2.56 birds/h (n
= 59 days). The largest movement rates (for all species combined) occurred during the first two
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weeks of sampling (August 15–31, Figure 5.1-10). Mean movement rates on individual days
ranged from 0.65 birds/h (September 2) to 150.34 birds/h (September 24). Passerines (excluding
Common Ravens) had the highest overall mean movement rate (5.31 ± 0.01 birds/h) of all
species groups. Sandhill Cranes (2.86 ± 2.52 birds/h) had the second highest overall mean
movement rate with all observations occurring on three days in late September (September 23
[3.46 birds/h], September 24 [148.32 birds/h], September 25 [16.90 birds/h]; Figure 5.1-13).
Eagles and other raptors had some of the lowest overall mean movement rates at 0.09 ± 0.02
birds/h and 0.18 ± 0.03 birds/h respectively. Eagle rates were highest from late September
through the first week of October (Figure 5.1-12). Movement rates of other raptors declined
during early September as falcon and Sharp-shinned Hawk numbers declined and then increased
and peaked toward the end of the month as Buteo activity increased (Figure 5.1-12). Overall,
waterfowl movement rates were low throughout the season. The seasonal mean movement rate
of swans was 0.52 ± 0.20 birds/h (Table 5.1-9), with only a small pulse of swan activity
occurring during late September (Figure 5.1-11). Only seven small flocks of other waterfowl
species and no shorebirds were observed during the entire fall sampling period.
Within days, non-corvid passerine movement rates were lower in late afternoon than earlier in
the day (ANOVA, F2, 153 = 27.02, P < 0.001; (Figure 5.1-19). Swans tended to move through the
area later in the day (ANOVA, F2, 153 = 2.94, P = 0.06), while other waterfowl tended to occur
earlier (ANOVA, F2, 153 = 2.58, P = 0.08). Within-day temporal variation in movement rates
were not found among other species groups (Figure 5.1-19). During the three days on which they
moved through the area, Sandhill Cranes migrated almost exclusively during midday, when 30 of
the 33 flocks (91 percent) were observed (G-test with Williams' correction; Gw = 27.49, df = 2, P
< 0.001).
5.1.2.2.2.3. Flight Altitude
The mean minimal flight altitude of all birds during diurnal visual sampling was 44.0 ± 4.1 m (n
= 540 flocks), with the highest mean altitudes for cranes (335.0 ± 142.2 m; n = 5 flocks), eagles
(204.3 ± 56.4 m; n = 21 flocks), and swans (149.0 ± 80.2 m; n = 10 flocks; Figure 5.1-20). Other
waterfowl had an intermediate mean flight altitude (100.0 m; n = 1 flock), whereas the lowest
mean altitudes were seen in other passerines (26.8 ± 2.1 m; n = 401 flocks), ravens (46.68 ± 8.5
m; n = 48 flocks), and gulls and terns (50.0 ± 0.0 m; n = 2 flocks).
5.1.2.2.2.4. Distribution and Patterns of Movement
The study team recorded flight paths of 947 flocks during fall diurnal visual sampling
(Appendices K–P). Overall flight directions of birds exhibiting straight-line flight (n = 412) were
variable but the largest percentage of flights (47.82 percent) were in an easterly direction (Figure
5.1-21). Species-groups showing the strongest easterly movement included cranes (87.50
percent), eagles (78.57 percent), swans (70.37 percent), and other raptors (68.75 percent). Other
waterbirds (50 percent) and passerines (41.83 percent) exhibited a weaker easterly movement in
the fall.
Most flocks of birds had flight trajectories crossing either north or south of the observation
station (n = 474; Appendices K–P). Of these flocks, 62.2 percent crossed south of the
observation station, whereas 37.8 percent crossed to the north (Table 5.1-9). Cranes, however,
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exhibited an equal percentage (50 percent) of northerly versus southerly crossings. In contrast to
all other species groups, ravens exhibited a higher percentage of northerly crossings (58.9
percent). Limiting the comparison to birds flying over the river channel or over the highlands
within 1.5 km north of the station, more raptors, cranes, and passerines were observed over the
channel than over the highlands (Table 5.1-9). Thus, many birds in the fall (with swans as a
notable exception) appeared to preferentially fly over and potentially follow the course of the
river.
5.1.2.2.3. Nocturnal Audiovisual Surveys
In the fall, the study team conducted crepuscular and nocturnal audiovisual sampling during the
first 2–3 h post-sunset during 50 nights. Far fewer birds (44 flocks, including single individuals)
were detected during fall nocturnal audio-visual sampling (Table 5.1-11) than during spring
sampling, with 28 (64 percent) individual passerines detected on two nights (August 24 and
August 25). Altogether, passerines composed 95 percent of all flocks detected. Mean audio-
visual detection rates for the season were 0.08 flocks/h during the first hour after sunset and 0.72
flocks/h during the second and third hours after sunset. Only three detections (two single
unidentified passerines and one Wilson's Snipe) occurred during the first hour post-sunset. Only
one detection (an unidentified passerine flight call) was non-visual. No bats were visually
detected during the fall crepuscular/nocturnal surveys. Night-vision goggles were used during all
nights for sampling periods more than 1.5 h after sunset and accounted for 19 detections of
individual passerines (all flying at altitudes of 10–70 m agl).
5.2. Breeding Season
5.2.1. Breeding Population Surveys
5.2.1.1. Aerial Survey Overview
During the lake-to-lake breeding population survey (hereafter breeding survey), total waterbird
densities (by water body surface area) were highest in the Denali Corridor and Watana Reservoir
survey areas (Tables 5.2-1 and 5.2-2). Densities in the Dam/Camp survey area also were high on
the first of two surveys, but were variable and highly sensitive to small changes in abundance
due to the area’s small aggregate water body size. Scaup (including both Greater and Lesser
scaup) were by far the most abundant species during both the first (June 1-5) and second (June
14-17) surveys, followed by goldeneyes (Common and Barrow’s) and American Wigeon (Table
5.2-2). Total bird density decreased between the first and second surveys, driven by a similar
decrease in density of scaup. For individual species, perceived and real changes in density
between the two survey periods were related to timing of arrival, dispersal, staging and departure
of breeding and/or transient birds, which varied among species.
Bird densities calculated from breeding population transect surveys (hereafter transect surveys)
east of the Oshetna River cannot be compared directly to densities from the breeding surveys
conducted in the rest of the study area, primarily because of differences in how the densities
were calculated (the former being based on total survey area size including dry land, and the
latter being based on surface area of water bodies only); and secondarily because of differences
in survey methods that affect detection rates. As with the breeding surveys in the larger study
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area, scaup were the most abundant species during both surveys (June2 and 15) in the transect
block (Table 5.2-3). However, in sharp contrast to patterns in the larger study area, density of
waterbirds in the transect block increased between the first and second surveys. Indicated totals
were substantially higher during the second transect survey for scaup, Surf Scoters, Bufflehead,
and Red-breasted Mergansers. Patterns likely differed between the lake-to-lake and transect
surveys because the latter were conducted over a small area, resulting in densities that were
sensitive to minor changes in abundance and to the use of a limited set of habitat types at specific
times.
5.2.1.2. Taxonomic Patterns
Scaup were mostly paired during the first breeding survey in early June, and large groups were
found on lakes typically used by migrants (Table 5.2-2). Total numbers decreased from 1,080
birds during the first breeding survey to 761 birds during the second; the number of pairs
decreased from 456 to 201, and the number of unpaired males increased from 160 to 327. Group
sizes on large lakes decreased as birds presumably dispersed into breeding areas, and the total
number of water bodies occupied by scaup increased from 101 to 126. The ratio of males to
females increased from 57 percent to 69 percent, suggesting that some females were likely
attending nests during the second breeding survey.
Similar patterns were observed for scaup in all survey subareas except the Chulitna Corridor
survey area, where total numbers increased slightly. The largest decline in numbers and density
occurred in the Watana Reservoir survey area, where 265 scaup were grouped on three large
lakes during the first survey (Pistol and two Fog lakes) but only 98 scaup occupied the same
three lakes during the second survey. Numbers of scaup increased from 16 indicated birds during
the first survey in the transect block east of the Oshetna River to 67 indicated birds during the
second transect survey (Table 5.2-3), suggesting that some scaup may have departed the larger
lake-to-lake survey area after the first breeding survey in early June. It is also probable that
reduced detectability of dispersed breeding pairs also contributed to lower numbers during the
second breeding survey.
The first breeding survey (June 1–5) appeared to be timed appropriately to describe the breeding
distribution of American Wigeon. A near-equal mix of pairs and lone males were recorded
during that survey, whereas mostly males were recorded during the second survey. Total
numbers increased from 162 birds during the first breeding survey to 196 birds during the
second, but the number of water bodies occupied by wigeon decreased from 43 to 29, and more
males were found in groups. One exception to the pattern of decreasing pairs was in the Denali
Corridor survey area, where both the number of males and the number of pairs increased on the
second survey. The total number of birds increased from 57 to 136 birds, but the number of
occupied water bodies was nearly unchanged, and 94 (69 percent) of birds observed during the
second survey were grouped on three water bodies.
Dabbling ducks as a whole followed a similar pattern to wigeon, generally shifting from pairs
and lone males during the first breeding survey to groups composed mostly of males condensed
to fewer water bodies during the second breeding survey. Total dabbling duck numbers increased
from between the two surveys, but the number of water bodies occupied by dabblers decreased
from 116 to 72. The percentage of males was 72 and 80 percent during the first and second
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breeding surveys respectively, suggesting that some females were attending nests during each
survey. The increase in total numbers likely resulted from increased detectability of flocked
birds, but a late arrival of breeding birds or of post-breeding males from outside the study area
may also have occurred.
The pattern of increasing numbers for dabbling ducks was not evident in the Chulitna Corridor or
Dam/Camp survey areas (Table 5.2-2). Declines were observed for wigeon, mallards and teal in
the Dam/Camp Area, and for all dabbling ducks in the Chulitna Corridor survey area. In the
latter area, 64 dabbling ducks were observed during the first breeding survey, compared to only 6
birds during the second. For dabbling ducks in general, unstable numbers between the two
breeding surveys likely resulted from grouping and movement of post-breeding males after early
June.
The breeding distribution of goldeneyes appeared to be captured more effectively by the first
breeding survey than by the second. The total number of goldeneyes increased modestly between
the surveys (Table 5.2-2), but the number of occupied water bodies decreased from 59 to 41.
Few females were observed during the second breeding survey, and many males were found in
groups. In the Gold Creek Corridor, 23 water bodies were occupied by a total of 44 goldeneyes
during the first breeding survey, but only 6 water bodies were used by 25 goldeneyes during the
second survey (19 were on Stephan Lake). In contrast, the number of water bodies occupied by
goldeneyes in the adjacent Watana Reservoir survey area remained nearly constant, but the
number of birds increased from 90 to 137, due primarily to the influx of males on two large lakes
in the Fog Lake group (a total of 102 males and 10 females were grouped on two lakes during
the second breeding survey). Numbers of goldeneyes and of water bodies occupied by
goldeneyes were relatively stable in the Chulitna and Denali corridor survey areas, but density
dropped in the Dam/Camp Area, where five birds were recorded on four different lakes during
the first breeding survey, and no birds were observed during the second breeding survey.
The total number of scoters decreased between the two breeding surveys, but the number of
males dropped only slightly (from 82 to 75 males). During the first breeding survey nearly all
scoters were paired, but during the second breeding survey about half of males were
unaccompanied by females. Most scoters during both surveys were observed in the Watana
Reservoir survey area.
All White-winged Scoters were paired during the first breeding survey, and 29 of 32 pairs were
grouped on three large lakes (Stephan and two Fog lakes). Total numbers dropped by nearly 60
percent on the second breeding survey (to 12 pairs and 2 lone males) and the remaining birds
occupied only four water bodies, including the same two Fog lakes as before. These results
suggest that at least some White-winged Scoters observed during the first breeding survey were
migrating through the study area.
In contrast to White-winged Scoters, Surf Scoter numbers dropped only slightly between the two
breeding surveys (Table 5.2-2) and the number of males increased. They were dispersed over a
larger number of lakes, thus it appears they were more likely breeding in the area. A total of 75
Surf Scoters (34 pairs, 5 males and 2 females) were distributed among 25 water bodies during
the first survey, and 72 Surf Scoters (18 pairs, 28 males and 8 females) occupied 19 water bodies
during the second survey. Numbers declined between the first and second breeding surveys in
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the Dam/camp, Denali Corridor and Gold Creek Corridor survey areas; but increased in the
Watana Reservoir survey area. Surf Scoters were seen on many of the same lakes during both
breeding surveys in the Watana Reservoir survey area, and the total number of occupied lakes
was unchanged; but small groups of males and a group of females were also observed during the
second breeding survey in the Fog lake group and Clarence Lake. Surf Scoters also increased in
the transect survey area, from 6 pairs during the first survey, to 10 pairs, 6 lone males, and 6
grouped birds during the second transect survey (Table 5.2-3).
Relatively few Black Scoters were observed, and locations varied between the two breeding
surveys. The largest single group was five pairs plus seven males in Molar Lake in the Watana
Reservoir survey area during the second survey, where none had been seen during the first
survey.
Bufflehead numbers increased sharply from 63 birds during the first breeding survey to 113 birds
during the second survey (Table 5.2-2). This increase may have resulted from a late influx of
pairs, as the numbers of pairs, males and females all increased. The number of water bodies
occupied by Bufflehead increased slightly from 26 to 29, and most water bodies contained 4 or
fewer birds during both breeding surveys. During the second survey, however, five mixed-sex
groups of 12–16 birds, comprising 39 males and 28 females, were also observed. The increase in
Bufflehead numbers was concentrated in the east end of the study area. The three largest groups
were in the Watana Reservoir survey area, and two of those were in water bodies near Goose
Creek near the east end of the Watana area. Numbers also increased further east, in the transect
block east of the Oshetna River, where no Bufflehead were observed during the first transect
survey, and 9 birds (indicated total 18) were observed during the second survey (Table 5.2-3).
Long-tailed Duck numbers were similar between the two breeding surveys (Table 5.2-2) and a
mix of pairs and lone males were observed during both surveys. The total number of males
increased from 32 to 40, and the number of water bodies occupied by Long-tailed Ducks
increased slightly from 25 during the first survey to 28 during the second. Little grouping was
apparent during either survey, with most observations consisting of singles, pairs and small
groups of <5 birds. Movements may have occurred among survey areas, as suggested by changes
in density and numbers of pairs in several survey areas, but the drop in density in the Denali
Corridor (where numbers were highest) resulted from the disappearance of females; pairs were
mostly observed during the first breeding survey and lone males during the second.
Trumpeter swan numbers and densities were highest in the Denali Corridor, particularly during
the second breeding survey when a flock of 14 swans plus several pairs and singles totaling an
additional 20 birds were observed in a series of ponds and sloughs adjacent to the Nenana River
(Table 5.2-2). Nineteen swans were observed in the same area during the first breeding survey.
Flocks of 9 and 10 swans were observed in Stephan Lake in the Gold Creek corridor during the
first and second surveys, respectively. Numbers were low in the Chulitna Corridor and
Dam/Camp survey areas both surveys (one pair was observed on the same lake both surveys in
the Dam/Camp Area, and one pair was observed in the Chulitna Corridor survey area during the
second survey). Pairs and singles were sparsely scattered throughout the other three areas during
both breeding surveys, and two small groups (four and five birds) were found in the Gold Creek
Corridor survey area during the second survey.
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Some grebes may have been attending nests during the first breeding survey on June 1–5. During
that survey, a total of eight Horned Grebes (two pairs and four singles) were dispersed among six
different water bodies, and nine Red-necked Grebes (two pairs and five singles) occupied seven
water bodies. Numbers of both species dropped substantially on the second breeding survey,
when only one Horned Grebe and no Red-necked Grebes were observed (Table 5.2-2).
Patterns were difficult to detect for some species occurring in low densities. Numbers were
stable between breeding surveys for mergansers and loons, but apparent changes within survey
areas could have reflected movements among areas, variable detection rates or both. Red-
breasted Mergansers increased in the Denali Corridor survey area, from one pair and two females
on three different lakes during the first breeding survey, to three pairs and three males on a single
lake during the second survey. In the Gold Creek Corridor survey area, reduced numbers of Red-
breasted Mergansers resulted partly from the disappearance of most females, which may have
been attending nests during the second survey. Indicated numbers of Red-breasted Mergansers
increased from zero during the first transect survey in the transect block east of the Oshetna
River, to 16 during the second (four males and four pairs; Table 5.2-3). Nearly all loons were
observed as singles or pairs during both breeding surveys, and numbers of all three species were
relatively stable between surveys, but with changes in numbers within some survey areas (Table
5.2-2).
5.2.2. Harlequin Duck Surveys
5.2.2.1. Spring Migration
Harlequin Ducks were first seen in the study area on May 11 when a pair was observed on the
Susitna River in the Gold Creek Corridor survey area, between Indian River and Portage Creek
(Figure 5.2-1, Table 5.2-4). On May 18–19, a total of 22 Harlequin Ducks were counted, 20 of
which were on the Susitna River and 2 of which were on the Oshetna River. About half of the 20
Harlequin Ducks seen on May 18–19 on the Susitna River were above the proposed dam site in
the Watana Reservoir survey area and the other half were below it in the Gold Creek Corridor
survey area.
Peak numbers of Harlequin Ducks occurred on May 23–24 when 554 individuals were counted,
521 of which were on the Susitna River. Slightly more than half of those 521 Harlequin Ducks
on the Susitna River were in the Gold Creek Corridor survey area and the remainder were in the
Watana Reservoir survey area (Figure 5.2-1, Table 5.2-4). Harlequin Ducks were found on eight
other streams on May 23–24: Indian, Jack, and Nenana rivers and Brushkana, Fog, Kosina,
Portage, and Seattle creeks. Of those eight streams, Brushkana Creek supported the highest
number with 14 ducks.
By May 28–29, the total number of Harlequin Ducks recorded on streams dropped to 210 ducks
and they were distributed on 17 different streams in the study area (Figure 5.2-1, Table 5.2-4).
The portion of the Susitna River in the Watana Reservoir survey area supported the most
Harlequin Ducks on May 28–29 (67 ducks), followed by Deadman Creek (27), Brushkana Creek
(26), and the Susitna River in the Gold Creek Corridor survey area (20).
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On all spring migration surveys, Harlequin Ducks were most often seen in pairs or groups of
pairs. Groups of 10–32 ducks were common on the Susitna River, particularly on May 23–24,
when more than half of the Harlequin Ducks sightings were in groups of that size (Figure 5.2-1).
Harlequin Ducks were found staging along the entire length of the Susitna River in the study area
and were commonly found at the confluence of a tributary (Figure 5.2-1). Harlequin Ducks
occupied tributaries as stretches of open water became available on them. Some ducks probably
were able to occupy breeding territories on tributaries after staging on the Susitna River while
other ducks moved to tributaries as a secondary staging area while waiting for breeding
territories in the upper reaches of streams to become available.
5.2.2.2. Pre-nesting
Thirty streams were surveyed for Harlequin Ducks during pre-nesting surveys, which consisted
of 25 named streams and 5 unnamed streams (Figures 5.2-2, Tables 5.2-5). Three of the 30
streams were not surveyed during the June 1–5 survey because of either time constraints, strong
winds in river drainages, or because it was questionable as to whether the stream was suitable for
pre-nesting Harlequin Ducks. The Study Plan (RSP Section 10.15.4.2.2) stated that surveys for
Harlequin Ducks would follow the entire length of tributaries where suitable nesting habitat was
present. That proved not to be feasible because suitable nesting habitat likely extends to the
upper reaches of most tributaries >10 mi from the study area and possibly includes most small
secondary and tertiary tributaries within and outside the study area. During pre-nesting and
brood-rearing aerial surveys in 2013, all primary tributaries of the Susitna and Nenana rivers
were surveyed and additionally many secondary tributaries, but tertiary tributaries within or
outside of the study area were not surveyed. What was considered suitable pre-nesting and
brood-rearing habitat for Harlequin Ducks within the study area was continually evaluated
during each survey and consequently, the extent of coverage of some streams differed among
surveys.
A Harlequin Duck nest was found on June 11during the Landbird and Shorebird Study (Section
10.16) on a small tributary of Watana Creek that was not surveyed during the aerial survey
because of its small size (Figure 5.2-2). The nest was on the ground at the base of a tree next to a
stream that was only about 3 ft wide. The line-of-sight distance to Watana Creek was 1 mi and
the downstream distance from the nest site to Watana Creek was 2.7 mi.
Harlequin Ducks were found on 20 of the 30 streams surveyed during pre-nesting and were
distributed throughout the study area, occurring in all 5 survey areas (Figure 5.2-2). A similar
number of Harlequin Ducks was recorded during the first pre-nesting survey on June 1–5 (173
ducks) and the second survey on June 14–16 (185 ducks), however, the distribution of ducks
differed within the study area between the two surveys (Table 5.2-5, Figure 5.2-2). On June 1–5,
most Harlequin Ducks were found in the Denali Corridor survey area (77 ducks) followed by the
Watana Reservoir (66), whereas on June 14–16, the Watana Reservoir had more ducks (114
ducks) than the Denali Corridor (33). Further, Harlequin Ducks were found on six streams in the
Watana Reservoir survey area on June 14–16 whereas no ducks were seen on those streams on
June 1–5. The coverage of streams on June 1–5 was not as extensive as on June 14–16, and some
of the sightings of Harlequin Ducks on the second survey were along stream sections that were
not surveyed on the first survey. In other areas where Harlequin Ducks were seen on June 14–16
and not on June 1–5, the coverage was similar. The remaining 20 percent of the Harlequin Ducks
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observed in the study area on each survey occurred in the Gold Creek Corridor, the Chulitna
Corridor, and Dam/Camp survey areas.
Of the four streams with the highest number of Harlequin Ducks on each pre-nesting survey (≥15
total ducks), three streams were the same between surveys: Deadman and Kosina creeks and the
Susitna River (Table 5.2-5). Brushkana Creek had 26 ducks on June 1–5 and the Black River had
29 on June 14–17. Most of the observations on Kosina Creek and all of the observations on the
Black River were outside of the 3-mi study area buffer (Figure 5.2-2). On other streams, like
Deadman, Brushkana, and Tsusena creeks and the Susitna River, Harlequin Ducks were found
distributed all along most of the entire length of the stream surveyed. Harlequin Ducks were seen
on a total of 15 different streams on June 1–5 and 19 different streams on June 14–16 (Table 5.2-
5).
Most of the Harlequin Ducks recorded during pre-nesting surveys were found in pairs. During
the first pre-nesting survey, 87 percent of the Harlequin Ducks were in pairs, whereas 68 percent
were in pairs on the second survey (Table 5.2-5). During June 1–5, a total of 75 pairs were
observed, with the highest numbers occurring on Deadman and Brushkana creeks (12 pairs
each), followed by the Susitna River (10 pairs), and Kosina Creek and the Jack River (7 pairs
each) (Figure 5.2-2). Groups of pairs were seen on most of these streams, which may indicate
that the location was serving as a staging site and ducks were not yet at breeding territories.
During June 14–17, a total of 63 pairs were counted with the highest number of 10 pairs
occurring on the Susitna River, followed by nine pairs on the Black River and five pairs each on
Kosina, Watana, Deadman, and Tsusena creeks (Figure 5.2-2). Pairs were distributed a little
more evenly along a stream on this survey compared to the first survey. Only four single females
were seen on the first survey and males not in pairs were seen either as singles, in groups of
males, or with pairs. Thirty-four single females and 27 males were seen on the second survey
(Table 5.2-5). A few single females were seen near pairs and males not in pairs were, like the
first survey, seen either as singles, in groups of males, or with pairs. On both surveys, Harlequin
Ducks were seen in clear and turbid waters and on sections of placid and fast-flowing streams.
Some Harlequin Ducks were found on beaver ponds in the upper stretches of tributaries.
5.2.2.3. Brood-rearing
During brood-rearing, Harlequin Ducks were found on 21 of the 28 streams surveyed (Figure
5.2-3). Some streams were not surveyed on one of the two brood-rearing survey or on both
surveys because of either time constraints, strong winds in river drainages, or because it was
determined that the stream was not suitable for brood-rearing Harlequin Ducks. One small
tributary of the Susitna River (R18) was not surveyed during either survey because it had very
little water in it during brood-rearing surveys. The Nenana River was not surveyed because it
was very turbid and was considered to be poor brood-rearing habitat. The Susitna River was
surveyed on the first brood-rearing survey but it too was very turbid and was not surveyed on the
second brood-rearing survey because it was considered to be poor brood-rearing habitat.
Broods were found on 15 of the 21 streams surveyed, with the highest number of four broods
observed on Devil Creek, followed by three broods each on Goose, Deadman, and Seattle creeks
(Table 5.2-6). Twelve broods were observed on the first brood-rearing survey on August 1–5 on
eight different streams and 27 broods were seen on the second survey on August 14–18 on 14
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different streams. For both brood-rearing surveys combined, at least 30 individual broods were
found in the entire area surveyed and just over half of the broods found on each survey were
within the 3-mi buffer of the waterbird study area (Figure 5.2-3). Broods were recorded in all
survey areas except the Dam/Camp Area.
The highest number of broods found in a survey area was 12 broods in the Watana Reservoir on
August 14–18 (Table 5.2-6). Broods were found on seven different streams in the survey area on
that survey. On August 1–5, seven broods were observed in the Watana Reservoir survey area on
four of the same streams where broods were seen on August 14–18, and additionally on Jay
Creek. Based on the age and locations of broods on each survey, the Watana Reservoir survey
area in total had 14 broods for the season: three broods on Goose Creek, at least two broods each
on Watana, Jay, Gilbert, and R21 creeks, and one each on the Black River, and Fog and R19
creeks (Figure 5.2-3). Additionally, females without young were found on Kosina and Tsisi
creeks and the Oshetna River.
In the Denali Corridor survey area, three broods were found on both Deadman and Seattle
creeks, and three and five females without young, respectively, were found on Jack River and
Brushkana Creek (Figure 5.2-3, Table 5.2-6). In the Chulitna Corridor survey area, four broods
were found on Devil Creek, two broods were found on Indian River, and one brood each on
Portage, Clark, and Tsusena creeks. Females without young on were observed on Thoroughfare
Creek. The only brood and Harlequin Duck observation in the Gold Creek survey area was on
Fog Creek.
On August 1–5, 12 of 50 females were associated with 50 young and on August 14–18, 27 of 36
females were associated with 106 young. The average brood size on the first survey was 4.2
young/brood and 3.9 young/brood on the second survey. Most broods seen on the first survey
were about 12 days old (range = approximately 8 to 26 days old) and on the second survey about
26 days old (range = approximately 8 to 39 days old). The start date of incubation was calculated
by subtracting the chick age from the survey date to obtain the hatch date and then subtracting 28
days for the incubation period (Robertson and Goudie 1999). Thus, the earliest start date of
incubation in 2013 was estimated to be June 10 and the latest was estimated to be July 9. The
Harlequin Duck broods from the early season nests were found in Jay, Fog, and R21 creeks.
These creeks had open water early in the season along some sections of the creeks and, on both
Jay and R21 creeks, Harlequin Ducks were staging on beaver ponds during pre-nesting surveys.
The average date of the start of incubation for all broods seen in the study area was June 26.
Broods with young chicks quickly took cover under overhanging branches when spotted from
the helicopter and some moved from the water into cover on shore. Because of the secretive
behavior of broods, particularly ones with young chicks, some broods probably were missed
during surveys. Other reasons that broods sometimes may not have been detected included the
dense vegetation covering some streams, sun glare on the water or reflective glare on the
helicopter window which obscured clear views of streams, and not getting bank-to-bank views of
the stream when tight sections of streams or windy conditions prevented the pilot from
maintaining a flight path parallel to the stream course.
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5.2.3. Brood Surveys
Two brood-rearing surveys were conducted during summer 2013 within a 1-mi area around and
including the Dam/Camp Area, the Watana Reservoir, and the Denali, Chulitna, and Gold Creek
corridor survey areas of the study area (Figures 4.1-1–4.1-3). A total of 499 water bodies were
surveyed on each survey, which resulted in an area of 5.7 mi2 of water bodies surveyed. The
survey team recorded broods of 24 species on the two surveys, including one species of swan, 15
species of ducks, three species of loons, two species of grebes, two species of gull, and one
species of tern (Table 5.2-7). A total of 111 broods were observed on July 20–22 and a total of
151 broods on August1–5. Between the two surveys at least 227 individual broods were found in
the waterbird brood survey area. The four most common species with broods (numbering more
than eight broods each) on each survey were scaup, goldeneyes, Green-winged Teal, and
American Wigeon, in order of abundance. For 11 of the 24 species with broods, only one brood
was observed on either or both surveys.
The Denali Corridor survey area contained most of the broods in the waterbird brood survey area
on both brood-rearing surveys; 61 percent of the broods on July 20–22 and 59 percent of the
broods on August 1–5 (Figure 5.2-4, Table 5.2-7). Broods of 18 species were observed between
the two surveys combined in the Denali Corridor survey area and a total of 68 broods were
observed on July 20–22 and 89 broods on August 1–5. Between the two surveys at least 138
individual broods were recorded, which was more than four times the number recorded in any
other survey area. The four most common species with broods in the waterbird brood survey
area—American Wigeon, Green-winged Teal, scaup, and goldeneyes—were also the most
common species with broods in the Denali Corridor survey area. Further, more than 60 percent
of the broods of American Wigeon, Green-winged Teal, and scaup were found in the Denali
Corridor survey area (Table 5.2-7).The number of broods found in the Watana Reservoir, and
Chulitna and Gold Creek corridor survey areas ranged from 9 to 19 broods on each survey. On
both surveys combined, broods of eight species were seen in the Watana Reservoir and Gold
Creek Corridor survey areas and nine species in the Chulitna Corridor survey area. Three broods
of three species were found in the Dam/Camp Area on July 20–22 and six broods of five species
on August 1–5 (Table 5.2-7).
Although the total number of broods was lower than in the Denali Corridor, the brood density
was higher in the Watana Reservoir survey area than any other survey area (40.7 broods/mi2;
Table 5.2-7). The density of broods in the Denali Corridor survey area on the first and second
was 30.5 and 39.9 broods/mi2, respectively. The Watana Reservoir survey area has the lowest
amount of water body surface area among the survey areas, except for the Dam/Camp Area, and
the number of broods relative to the amount of water is high. The Dam/Camp Area had a higher
density of broods on both surveys than the Gold Creek Corridor survey area, which had five
times the amount of water body surface area.
Broods of eight species (Trumpeter Swan, Northern Shoveler, Long-tailed Duck, Bufflehead,
Red-throated Loon, Bonaparte’s Gull, Mew Gull, and Arctic Tern) were only found in the Denali
Corridor survey area (Table 5.2-7). Seven other species were only found in one of the other four
survey areas: Red-breasted Merganser in the Dam/Camp Area, White-winged Scoter and Horned
Grebe in the Watana Reservoir survey area, Gadwall and Black Scoter in the Chulitna Corridor
survey area, and Pacific Loon and Red-necked Grebe in the Gold Creek Corridor survey area.
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Broods of three species were found in all five survey areas (Mallard, Green-winged Teal, and
goldeneyes) and broods of scaup and Common Loon were found in all survey areas except the
Dam/Camp Area.
Ten water bodies in the Denali Corridor survey area contained three or more different broods
either on one survey or both surveys combined (Figure 5.2-4). The highest number of broods
recorded on a water body on a single survey was nine broods on July 20–22. This water body
was located at the divide between the Brushkana and Deadman creek drainages. Many other
water bodies in this area supported multiple broods, including a couple of large shallow water
bodies that are connected to Brushkana Creek (Figure 5.2-4). Large numbers of scaup broods
were found in this area. Another area in the Denali Corridor survey area that supported multiple
scaup broods and the broods of four other species were a couple of lakes adjacent to the Denali
Highway (Figure 5.2-4). Additionally, lakes adjacent to lower Deadman Creek and in the
drainages just west of Deadman Mountain were important brood-rearing areas too. Within the
other four the survey areas, broods were found on lakes throughout each survey area with no
more than three broods found on one lake during a survey (Figure 5.2-4).
During brood-rearing surveys, chicks from duck broods were classified into seven different age
subclasses based on plumage development (Table 5.2-8). Class 1, which is made up of 1A, 1B,
and 1C, is a stage when chicks are downy with no visible feathers. Class 2, which is made up of
2A, 2B, and 2C, is a stage when chicks are partially feathered. In Class 3, chicks are fully
feathered. On the first brood survey on July 20–22, 80 percent of the broods were in the Class 1
category, which roughly equates to an age range of 1–20 days old. The age range related to each
subclass varies by species. On the second brood survey on August 1–5, 64 percent of the broods
were in Class 2. All the remaining broods except for one were in Class 1.
The midpoint of that age range is used to calculate hatch date by subtracting the chick age from
the survey date and then an incubation start date by subtracting the duration of the incubation
period. Dates for the start of incubation were calculated for a selection of species in which chick
ages are associated with subclass categories and where a sample of greater than five broods was
available (Gollop and Marshall 1941, Lesage et al. 1997). Northern Pintails were the earliest
nesters with a median incubation start date of 31 May (n = 12 broods), followed by Mallard with
a date of June6 (n = 9). Three species had a median incubation start date of June10, which
included American Wigeon (n = 18), Surf Scoter (n = 6), and goldeneyes (n = 29). Green-winged
Teal had a median incubation start date of June 20 (n = 36) and scaup was June 21 (n = 74).
Dabbling ducks like Northern Pintail, Mallard, American Wigeon, and Green-winged Teal are
usually considered early nesters and diving ducks like scaup, Surf Scoter and goldeneyes are
considered late nesters. Because of the delay in the availability of open water and snow-free
ground in the study area in 2013, many dabbling ducks may have started nesting later than
average. The nesting phenology of diving ducks may have been similar to an average year in the
study area.
5.3. Information for Mercury Study
A literature review conducted by the study team on the food habits of the waterbird species that
occur in the study area indicated that fish were likely to compose 40 percent or more of the diets
of these species: Common Loon, Red-throated Loon, Red-necked Grebe, Common Merganser,
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Red-breasted Merganser, Bonaparte’s Gull, and Arctic Tern. Accordingly, these seven species
were identified as the best candidate species for collection of feathers for laboratory sampling of
mercury content.
Only a single nest and few broods of these piscivorous waterbirds were found during the
breeding, brood, and fall migration waterbird aerial surveys in 2013 (those surveys focused on
locating adult birds and broods, rather than nests). One Common Loon nest was found in the
Watana Reservoir survey area, but could not be visited because it was located on CIRWG lands.
Broods of all seven species of piscivorous waterbirds were observed in 2013, but the nest
locations were not found. Loons and grebes often return to the same nest lake each year, so lakes
where broods were observed in 2013 can be targeted during aerial surveys in the next study
season to look for nests. Merganser broods were found in all five survey areas, with most broods
(nine) occurring in the Gold Creek Corridor, followed by the Denali Corridor (six), Watana
Reservoir and Gold Creek Corridor (four each), and the Dam/Camp Area (one).
Seven broods of Common Loons were found in the study area, located in all survey areas except
the Dam/Camp Area. Two Red-throated Loon broods were found in the Denali Corridor survey
area. Three broods of Red-necked Grebes and an unidentified brood of grebes were found in the
Watana Reservoir survey area. Two other unidentified grebe broods were found in the Denali
Corridor survey area and a Red-necked Grebe brood was found in the Gold Creek Corridor
survey area. All of the gull and tern broods found in 2013 were in the Denali Corridor survey
area: three broods of Bonaparte’s Gulls, two brood of unidentified gulls, and one brood of Arctic
Terns.
6. DISCUSSION
6.1. Spring and Fall Migration
6.1.1. Aerial Surveys
The data collected in 2013 during spring and fall aerial surveys fulfilled the study objectives to
document the occurrence, distribution, abundance, habitat use, and seasonal timing of waterbirds
migrating through the Project area. Spring and fall migration aerial surveys for waterbirds were
conducted at a frequency of every 5–6 days, which effectively identified important staging areas
and documented the timing of migration and the distribution and abundance of waterbirds.
Because snow and ice cover persisted much longer than average in south-central Alaska during
spring 2013, spring migration in 2013 may have been more compressed than in an average
spring. Furthermore, the arrival of peak numbers of early migrant waterbirds may have been later
than average. From late April to mid-May, very little open water was available to waterbirds in
the study area and waterbirds were concentrated at a few open-water areas on water bodies and
streams. The first open water on large lakes was at outlet and inlet areas and those locations
gradually supported more waterbirds with each successive spring survey. The amount of open
water on rivers increased more rapidly than on lakes and between the first and third week in
May, rivers supported more waterbirds than lakes. The Nenana and Susitna rivers were the most
important rivers for staging waterbirds during May because of the development of leads in river
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ice. At that time, the water in these two rivers was clear and leads served as foraging sites for
waterbirds while ice adjacent to leads provided resting sites. On the May 23–24 spring migration
survey, 47 percent of the waterbirds in the study area were staging on the Susitna River. During
late May, warm temperatures caused rapid snow melt and the breakup of rivers happened
quickly. Rivers became less suitable for staging and by the last migration survey on May 28–29,
just over three-quarters of the waterbirds were found on lakes.
In general, the pattern of use of the study area during spring in 2013 was similar to that recorded
in 1981 during the APA project (Kessel et al. 1982). Kessel et al. (1982) noted early migrants
used the Susitna River and the thawed edges of lakes, and that use of most of the water bodies
did not increase until the end of May. The Susitna River was not surveyed in the 1980s and so
the timing and the magnitude of use by waterbirds at that time is unknown. The selection of lakes
surveyed in the 1980s during spring and fall migration was considerably less compared to 2013,
but overall the species composition recorded between the two studies was similar (Kessel et al.
1982).
One interrelated study was described in the Study Plan that could potentially inform the
Waterbird Migration, Breeding and Habitat Use Study. It was anticipated that information from
the study of ice processes in the Susitna River (Study 10.7.6) would be helpful in scheduling the
start date of spring migration surveys. However, because spring breakup was delayed in the
study area in 2013, migration surveys commenced prior to availability of open water, so
information from the ice processes study was not needed.
Fall migration surveys in 2013 documented the use of water bodies by waterbirds in the study
area from mid-August to mid-October. Waterbirds were distributed throughout the study area
during most of the fall until the freeze-up of water bodies restricted birds to large lakes that still
had open water. Numbers of waterbirds were highest from mid-August until the third week of
September. Numbers remained steady from late September until the second week of October
when totals dropped to fewer than 600 birds. In general, the pattern of fall movement for most
waterbirds species in 2013 was similar to the pattern recorded in the 1980s (Kessel et al. 1982),
whereby the numbers of most dabbling ducks (except for Mallards) peaked in early fall and the
movement of swans through the study area occurred between mid-September and early October.
Some large lakes in the study area were surveyed during spring and fall in the 1980s and in 2013.
A relative importance value was determined for these lakes based on calculations that were
developed for the APA project (Kessel et al. 1982). Four of the top five lakes of relative
importance in the 1980s also ranked in the top five lakes of relative importance during spring and
fall 2013:Murder, Stephan, and Clarence lakes, and a lake in the Fog Lakes group. Counts of
waterbirds on those four lakes in 2013 during peak periods ranged from 100–200 during spring
and 100–400 during fall. The highest species diversity recorded on a single survey in 2013 was
at Stephan Lake where 17 species were found in late May and 12 species in mid-August.
The highest count of waterbirds recorded on a single survey during spring and fall in 2013 was
between 2,000 and 3,000 birds. For spring the peak count occurred in late May and for fall,
counts peaked from mid-August to mid-September. Ducks were the most abundant species group
during spring and fall, followed by swans, loons, and grebes. Geese and gulls were mostly
observed during spring. Single-species groups of 31–100 ducks were observed on every spring
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survey from early to late May and all 11 of the fall migration surveys. Large, single-species
groups of Northern Pintail and Northern Shoveler were observed only in spring and large groups
of Green-winged Teal were observed only in fall. Groups of Mallards and American Wigeon
were seen during both seasons. For diving ducks, the only species observed in large groups
during spring were scaup. During fall, large groups of scaup were common and groups of
goldeneyes and merganser also were observed occasionally. Swans were observed in pairs or
small groups during spring. During fall, a couple of groups of 53–76 swans were seen on Murder
and Stephan lakes in late September. Snow Geese were the only goose species seen in a large
group (80 birds) and that group was observed flying over the study area during late May. Snow
Geese are migrants in the study area and were not present during the breeding season. Eight
other species were recorded as migrants because they also were seen only during the migration
season. All of the other 30 species were recorded in the study area during the breeding season
and 27 of those species were confirmed breeders. Whether the large groups of ducks and swans
in the study area during spring and fall migration are migrants or local breeders is not known.
Regardless, many streams and water bodies within the study area were locally important staging
areas for waterbirds before and after the breeding season.
6.1.2. Ground-based Surveys
These studies provide the first comprehensive survey of bird migration for the Upper Susitna
River Basin. For the APA project (Kessel et al. 1982), avian surveys of the region concentrated
on breeding season studies, although aerial surveys of water bodies were conducted in spring and
fall to determine usage by migrating waterbirds. Results are also available for several other bird
migration studies in central Alaska that used methodologies similar to those described here and
provide some context for the results of this study (Appendices Q–S). Comparisons of the results
of this radar study with those of other studies are presented below.
While these comparisons are useful in providing a general context for understanding patterns of
bird migration in the region, it should be borne in mind that comparisons among these sites may
be confounded by variation in study dates, study duration, categorization of species, analytical
methods, and radar technology, as well as by extrinsic factors such as annual variation and site
characteristics that may influence detectability. For these reasons, caution is warranted when
interpreting these studies.
6.1.2.1. Species Composition and Abundance
Although the fall survey period was 16 days longer than the spring survey period, differences in
average day length resulted in equal time being sampled during both seasons. The number of
flocks observed in spring (2,366) was double the number observed in the fall (1,234). Total
numbers of individuals observed, however, were more similar between the two seasons,
indicating that mean flock sizes were larger during the fall. This result is largely due to the
prevalence of Common Redpoll flocks in the fall, as they constituted less than 5 percent of flocks
and individuals in the spring but almost 20 percent of all flocks and 30 percent of the total
number of individuals in the fall. In both spring and fall, non-corvid passerines composed the
majority of flocks observed, as well as 40 percent of individuals in the spring and 59 percent of
individuals in the fall. In the spring, waterfowl also were numerous, composing 32 percent of the
total number of birds observed; and shorebirds (14 percent) were the only other group
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representing more than 10 percent. In the fall, only Sandhill Cranes (27 percent) and passerines
represented more than 6 percent of the total observed.
The study team recorded 183 groups of birds during post-sunset periods in the spring and 44
groups during the same time of day in the fall. In the spring, passerines, ducks, and shorebirds
(primarily Wilson's Snipe) composed the majority of flocks observed at night, whereas
passerines comprised nearly all nocturnal observations in the fall. During much of the spring
season, crepuscular light conditions allowed for continued use of binoculars and unaided visual
scanning for observations of birds out to several kilometers (to the north) for 2–3 h after sunset.
In the fall, darkness precluded use of binoculars after the first hour post-sunset, and detectability
of birds was thereafter more limited by the restricted field of view and detectability distance
(e.g., limited to within ~100 m for passerine-sized birds) of night-vision goggles. Although
detectability differences contributed to the differences in numbers of birds observed in the two
seasons, relative abundances of the species groups reflected those during diurnal sampling as
well. In two studies north of the Alaska Range, fewer birds (predominantly passerines) were
observed visually after sunset in the spring than during fall migration studies (Shook et al. 2009,
2011).
6.1.2.2. Species Groups
The study team recorded 93 species of birds during the spring and fall migration periods of 2013.
A number of these were year-round residents and/or local breeders, and observations of these
likely include multiple observations on single individuals and groups. Many of these bird species
differ in flight behaviors, flock sizes, altitude and timing of flights, and seasons of use. The
following discussion presents information on four species groups that pass through the area. The
prioritization and selection of these groups was based on abundance, and/or their conservation
and protection status. Species groups discussed include waterfowl (with emphasis on Trumpeter
and Tundra swans), Sandhill Cranes, raptors (with emphasis on Bald and Golden eagles), and
passerines.
6.1.2.2.1. Swans and Other Waterbirds
Kessel et al. (1982) suggested that the Upper Susitna River Basin was not a significant flyway
for migrating waterfowl, and results of the migration surveys conducted in 2013, in comparison
with other migration studies in central Alaska (Appendices Q and R), generally support this
assertion. Waterfowl accounted for 32 percent of individual birds observed in spring, but the
total number of individuals (2,658) was lower than reported in nearly all other studies.
Waterfowl numbers in fall (372, 6 percent of all birds) were substantially lower. Results of aerial
surveys in 1981, 1982, and 2013 (Table 5.1-6) indicated that fewer waterfowl used water bodies
of the upper Susitna River basin for stopover in the spring than in the fall; however, the results of
ground-based surveys conducted in 2013 suggest that more birds fly through the region in the
spring than in the fall. During spring 2013, swans (47 percent) and scoters (23 percent)
accounted for the majority of identifiable waterfowl observed, but only accounted for 1 percent
and 8 percent, respectively, of waterfowl seen during aerial surveys of the area in spring 1981
(Kessel et al. 1982) and 4 percent and 2 percent, respectively, of waterfowl seen during aerial
surveys of the area in spring 2013 (see Aerial Survey Results, this study). These results suggest
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that some species primarily migrate through the basin without stopping-over at local water
bodies.
Swans accounted for 41 percent of waterfowl observed in the spring and 81 percent of waterfowl
observed in the fall. Trumpeter Swans breed locally, and both Trumpeter and Tundra swans
migrate through the region to and from breeding areas in western Alaska (Ely et al. 1997, Kessel
et al. 1982, Bellrose 1976). Although swans accounted for 13 percent of all species recorded
during the spring migration period, the total number observed across the season (1,086) was
lower than reported from comparable studies in the region (Appendix Q), most of which were
located north of the Alaska Range, within the Tanana River basin, a well-documented migration
corridor (see Cooper et al. 1991). Few migration studies have been done south of the Alaska
Range, however, and none have been conducted in the Talkeetna Range where the Project would
be located.
It is unlikely that the 2013 sampling season failed to encompass all of the spring migration of
swans, because extended winter weather and record late ice break up regionally also delayed
much of the spring 2013 bird migration, resulting in few swans moving through the region until
early May, two weeks after initiation of surveys. Spring swan numbers, however, were reduced
by low visibility conditions throughout the day on May 3, during which 16 different flocks of
swans, including both species, were recorded passing; but only one group of 29 birds was
observed and accurately counted. Because flocks of up to 200 individuals were observed on
subsequent days, and no more than 12 flocks were seen or heard during any other day of the
season, it seems certain that a substantial proportion of the total number of swans flew through
the survey area untallied during that single day. In contrast to the May peak reported here, other
studies observed peak dates of swans occurring more than a week earlier, during ~April 23–27
(Appendix Q).
In the fall, far fewer swans (301 birds) were observed moving through the study area than in the
spring; and the fall 2013 count also was low in comparison to other fall migration studies
(Appendix R). Given that water bodies in the region were yet unfrozen at the end of the survey
period, it is possible that additional movements of swans may have occurred after surveys ended
in mid-October. Among five central Alaskan studies with survey seasons extending later in
October, however, dates of peak swan migration ranged from September 28 to October 13
(Cooper et al. 1991), all of which are well before the final day of surveys for this study.
Swan mortality resulting from collisions with power lines and other artificial structures has been
documented across much of North America and Europe (Avery et al. 1980, Erickson et al. 2005),
although such mortality events appear rare in Alaska (Cooper et al. 1991, Ritchie and King 2000,
Shook et al. 2009). Directional, spatial, and altitudinal flight patterns are therefore important
factors in assessing potential collision risk for birds present in an area. As with most migrating
species during the survey, swan movements were strongly directional in both seasons along an
east/west axis. In both seasons, more swans were observed south of the visual observation station
than to the north. In spring, this appeared to be a result of birds concentrating along the river
channel, but in the fall more birds tracked parallel to but south of the channel (Appendices D and
K; Table 5.1-9).
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In the spring, swans generally flew at higher altitudes than most species, with a mean flock flight
height of ~250 m agl and a quarter of flocks flying less than 100 m agl. Flight altitudes in the
spring were similar to those recorded at the Eva Creek wind development near Ferry (Shook et
al. 2011), but higher than reported elsewhere along the Tanana River Valley or at Fire Island, in
Cook Inlet (Appendix S). In the fall, the mean flight altitude for swans was 150 m agl, with
almost half the flocks flying less than 100 m agl, and similar to that reported for most other
migration studies in the region (except lower than observed at Eva Creek; Appendix S). It is
possible that variability in the mean flight altitudes of swans observed during the survey, both
within and between seasons, may reflect species differences as well. Trumpeter Swans, which
breed locally, generally were observed at lower flight altitudes and constituted a greater
proportion of swans identified to species in the fall than in the spring.
Ducks accounted for 43 percent of waterfowl and 44 percent of all birds observed in the spring
but only 3 percent of waterfowl and <1 percent of all birds observed in the fall. Geese composed
12 percent of the total number of waterfowl and 4 percent of all birds in the spring, and only 6
percent of waterfowl and <1 percent of all birds in the fall. Five percent of waterfowl in the
spring and 13 percent in the fall were observed at too great a distance to determine if they were
ducks or geese. The total number of ducks observed in the spring (1,136) was intermediate
relative to numbers observed during previous migration studies in the region (Appendix Q);
however, numbers of geese seen during this study were much lower than observed during most
other spring studies. In the fall, numbers of both ducks and geese were much lower than reported
during nearly all previous fall migration studies in the region (Appendix R). For both seasons,
numbers of waterfowl were within the lower range of numbers observed during three years of
surveys at Gulkana, which is also located south of the Alaska Range, 110 mi east of the Project
site. The relatively low numbers of geese observed during this study can be attributed largely to
Greater White-fronted Goose migration being more prevalent north of the Alaska Range than to
the south (Cooper et al. 1991).
Flight directions of geese in spring were predominantly westerly; however, those of ducks were
bimodal along the east-west axis, with most flocks flying in an easterly direction. Approximately
equal numbers of dabbling duck flocks were observed flying to the east and west, but flight
directions of diving ducks, scoters in particular, were strongly easterly, suggesting that sea ducks
migrate from coastal areas to the south or west before heading to inland breeding areas.
Supporting this hypothesis further, most loons also were observed flying easterly in the spring.
Flight directions of larids, however, were bimodal along the east-west axis in the spring. Most of
the larids observed were Herring Gulls, however, which often exhibited patterns of movements
up river (easterly) in the morning and westerly (later in the day), potentially reflecting daily
transit between nocturnal roosting sites and diurnal foraging areas.
Shorebirds migrated through the area during a two-week period in mid-May, in higher numbers
than have been reported during most other migration surveys in central Alaska (except Tok in
1987 and 1989; Cooper et al. 1991; see Appendix Q). Although the species composition could
not be determined for the majority of shorebirds observed, at least 10 species were represented
among the flocks recorded. No shorebirds were observed during diurnal surveys in the fall; the
only fall observation being a single Wilson’s Snipe observed during an early evening audiovisual
survey session in early September. Few shorebirds have been observed during fall migration
studies elsewhere in the region as well (Appendix R); although these studies, as well as the
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current efforts, likely missed a large portion of the fall shorebird migration period, which
generally begins in late June.
6.1.2.2.2. Sandhill Cranes
In the spring, Sandhill Cranes appear to migrate through Interior Alaska in a broad front and are
less concentrated than they are in the fall. In the fall, birds breeding in western Alaska must fly
toward the northeast, around the northward curve of the Alaska Range, then swing to the
southeast to exit the Tanana Valley. Cooper et al. (1991) conducted several years (1987–1989) of
extensive bird migration studies during spring and fall migration at Gakona (near Gulkana) and
stated that “almost no cranes fly over the Gulkana study area during migration.” Low numbers
also were observed at Fire Island during spring (83 individuals) and fall (111 individuals)
migration (Day et al. 2005). This study recorded low numbers of Sandhill Cranes migrating
through the study area during spring (23 individuals) and fall (1,754 individuals).
In contrast to the study area, Sandhill Cranes appear to move in large numbers north of the
Alaska Range. The Tanana Valley is a well-known spring and fall migration corridor for the
mid-continental population of Sandhill Cranes (Kessel 1979, 1984; Cooper et al. 1991). The
number of birds moving through the region is on the order of 150,000 birds in the spring and
200,000 birds in the fall (Kessel 1984). A variety of sites north of the Alaska Range have
recorded high numbers of cranes during spring and fall (Appendices Q and R), including Tok
[(1987: 113,167; 97,988) (1988: 31,311; 43,442) (1989: 97,970; 67,776; Cooper et al. 1991)];
Eva Creek (12,757; 48,276; Shook et al. 2011); Delta Junction (31,163 spring only; Parrett et al.
2009); the Golden Valley Electric Association Northern Intertie corridor (GVEA Intertie;
30,509; 84,979; Day et al. 2011), whereas a site along the Delta River in the Alaska Range had
much lower numbers during spring and fall migration (339; 200; ABR 2010).
The timing of peak spring migration for cranes has been relatively consistent for sites in Interior
Alaska, during May 4–11 in spring (Appendix Q) and September 10–23 in fall (Appendix R).
Peak crane movements in this study fell within the spring range (May 9) and just outside the fall
range (September 24).
Mean flight altitudes of migratory cranes have varied from 76 m agl at a coastal location (Fire
Island) to 113–201 m agl (Tok) to 364 m agl at Eva Creek (Appendix S). This study only had
one Sandhill Crane observation within 1 km of the observation point, which was recorded at a
minimum flight altitude of 100 m agl; thus, it is not possible to make any broad generalizations
about crane altitudes in this study. Cranes at greater distances had significantly higher estimated
mean minimum flight altitudes (>500 m agl in both spring and fall) but altitude estimates at such
distances were probably less accurate than those made nearby.
6.1.2.2.3. Raptors
Although they accounted for only 6 percent of all birds recorded in spring and 3 percent in the
fall, raptors were second to passerines in the frequency of occurrence throughout the study and
were seen during 96 percent of survey days in the spring and 74 percent of survey days in the
fall. Of birds identified to species, Golden (25 percent) and Bald eagles (24 percent) were the
most frequently observed raptors in the spring. Together with unidentified eagles they
represented 48 percent of all raptors and 3 percent of all birds seen in the spring. Relatively
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fewer Golden Eagles (9 percent of identifiable raptors) were seen in the fall, when Bald Eagles
(24 percent of raptors), Peregrine Falcons (16 percent), and Sharp-shinned Hawks (14 percent)
were relatively more numerous.
Movement rates of raptors in the Project generally were within the range of rates observed
elsewhere in Alaska during spring and lower than rates observed elsewhere during the fall
(Appendices Q and R). As with other species groups, spring raptor migration occurred late in
2013. Peak movement rates occurred in May rather than April, as reported for previous studies in
the region (Appendix Q). The increase and peak in raptors in late September suggests that fall
raptor migration largely fell within the range of Project-wide survey dates. Mean minimum flight
altitudes observed during this study also differed from mean flight altitudes reported elsewhere,
generally being higher in the study area than observed at other locations within the region
(Appendix S). Higher movement rates of many raptors after May 15, however, may be inflated
by the presence of local breeders rather than represent late migrants, and mean flight altitudes
also may differ among migrating and local individuals. Raptor migration counts conducted at
other points within the study area overlapped temporally with the surveys reported here during
the spring period from April 20 through May 15 and during the fall from September 15 through
October 15. Further discussion of raptor migration in the study area is presented in ISR Study
10.14, Surveys of Eagles and Other Raptors.
6.1.2.2.4. Passerines
Migration routes of passerines in Interior Alaska are poorly known, but they appear to migrate
over a broad front for an extended period from early April through late May and during August
through early October (Cooper et al. 1991). The spring and fall survey periods in 2013
encompassed the peak dates of passerine migration reported elsewhere in central Alaska
(Appendices Q and R), and the seasonal patterns of daily mean movement rates during this study
suggest that the sampling period encompassed nearly all of the passerine migration period in the
spring. Diurnal visual movement rates of passerines in the fall were highest during the first week
of sampling, and 10 species observed during spring sampling were not recorded during the fall
(compared to three species in the fall that were not observed earlier in the year), suggesting that
some early season fall migration of passerines may have been missed.
Relative abundance of passerines during migratory seasons has not been studied well in the
Project area and counts of 3,369 and 3,913 during the 2013 spring and fall migration seasons,
respectively, begin to provide some baseline information. A variety of sites north of the Alaska
Range have recorded variable numbers of passerines during spring and fall including Tok [1987:
9,275, 9,318]; [1988: 7,030, 5,959]; [1989: 9,290, 7,052]; Cooper et al. 1991); Eva Creek wind
development near Ferry (493, 1,252; Shook et al. 2011); Delta Junction (911; spring only; Parrett
et al. 2009); and Delta River, a site within the Alaska Range (270, 460; ABR 2010). One site
south of the Alaska Range (Gulkana) recorded lower numbers of passerines during spring and
fall migration ([1987: 357, 866]; [1988: 912, 600]; [1989: 675, 628]; Cooper et al. 1991);
however, these results (as well as those at Tok) only included passerines observed within 100 m
of the survey station.
Peak passerine movements in this study were later in the spring (May 17) than reported for other
migration studies (ranging from April 28 to May 11) in central Alaska (Appendix Q), which
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likely corresponds to the late onset of spring-like conditions across the state in 2013. Within the
study area , the area surveyed was largely snow-covered at almost all elevations until late May in
2013. The peak dates of fall passerine movements were highly variable among different studies
and years (Appendix R), likely due to variable relative abundances of species with different
migration chronologies. Half of the studies in the region, including the survey reported here,
however, had a peak passerine migration date between September 10 and September 15.
The mean minimum flight altitude of passerines observed in the spring (51 m agl) was
significantly higher than mean altitudes reported from other spring migration studies in central
Alaska (range 16–28 m agl), while the mean for the fall migration survey at the Project (27 m
agl) was mid-way within the range (19–38 m agl) reported elsewhere (Appendix S). The higher
spring flight altitudes may be associated with the topography near the visual sampling station,
which included the river gorge. Minimum flight altitudes of birds that flew along the river
channel (particularly swallows in the spring), often were recorded as higher than 50 m agl,
although their flight heights relative to the observers were generally much lower or even
negative.
Mean flight altitudes of migratory passerines are typically the lowest among species groups
observed during terrestrial visual studies; however, these results tend to be biased by the limited
detectability range for smaller birds. Concurrent radar observations demonstrate that most
migrants, and smaller birds in particular, will not be detected by visual observers. Even within a
short horizontal distance from the observer, many, and often most individual passerines will fly
at altitudes high enough to be undetected. Although other types of studies confirm that passerines
tend to migrate over land at lower altitudes than other species groups (Kerlinger 1995), the
difficulty in observing smaller birds at greater distances and altitudes also results in mean
altitude estimates that are biased low. The flight altitude of passerines also can be biased by the
inclusion of local or foraging birds that tend to fly at lower altitudes due to the local nature of
their flights and may be difficult to distinguish from migratory flights.
6.1.2.3. Radar Passage Rates
Passage rates are an index of the number of targets (birds) flying past a location and are a
widely-used metric in studies of migration activity (Day et al. 2005, Day et al. 2011, Shook et al.
2011). Thus, passage rates allow for comparisons of bird use among different sites and regions.
In this study, target characteristics observed at the 1.5-km range as well as the relatively low
numbers of radar targets observed greater than 1.5 km from the radar (representing larger-bodied
birds and flocks) indicate that nocturnal radar passage rates primarily reflect passerine migration
rates.
Radar observations indicate that low numbers of birds migrate through the Project during diurnal
periods of spring and fall migration. The diurnal radar surveys recorded passage rates of 31 and
11 targets/km/h during spring and fall, respectively. A similar pattern was found at Eva Creek
(42 and 10 targets/km/h during spring and fall, respectively; Shook et al. 2011). No other diurnal
mean passage rates are available from Alaska for comparison.
The nocturnal radar surveys recorded passage rates of 114 and 119 targets/km/h during spring
and fall, respectively, at the Project. For comparison, spring and fall nocturnal passage rates at
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other locations in Alaska include Eva Creek (148 and 198 targets/km/h), Delta River
(approximately 27 targets/km/h during 10days of peak fall migration; ABR 2010), and Fire
Island (14 and 7 targets/km/h; Day et al. 2005). Nocturnal mean passage rates were not
calculated from studies in Tok and Gulkana (Cooper et al. 1991), but passage rate by date are
available in this report. No additional studies are available for comparison in Alaska; however,
fall radar migration rates at a continental scale are reported by Johnston et al. (2013). The lack of
additional studies for comparison in this region, highlights the general lack of information on
nocturnal migration passage rates in Alaska and the western US and warrants the cautious
interpretation of comparisons with the few studies that are available.
6.1.2.4. Flight Directions
Flight directions in both the spring and the fall were consistent with expectations during both
radar surveys and diurnal visual surveys. In the spring, the mean flight direction on radar was
255° during the day and 268° at night; during visual surveys, 83 percent of all flocks seen during
the daytime flew in a westerly direction, which is consistent with flight paths of birds migrating
to Western and Interior Alaska from their winter ranges. In the fall, the mean flight direction on
radar was 042° during the day and 088° at night; during visual surveys, with 80 percent of all
flocks seen during the daytime flying in an easterly direction. For comparison, the main axis of
the Upper Susitna River Basin in the vicinity of the survey area is essentially east–west
(90°/270°), suggesting that these birds were following the predominant orientation of the river
channel in both seasons.
6.1.2.5. Radar Flight Altitudes
Flight altitudes are critical for understanding the vertical distribution of migrants in the airspace
and have implications for collision risk assessment and other predictors of disturbance for
migrating birds. Large numbers of birds found dead at tall, human-made structures (generally
lighted and guyed communications towers; Avery et al. 1980) and the predominance of nocturnal
migrant passerines among such fatalities (Manville 2000; Longcore et al. 2005) indicate that
large numbers of these birds fly lower than 500 m agl on at least some nights. Radar studies have
confirmed that most nocturnal migration occurs below approximately 1.0–1.5 km agl (Larkin
2006, Mabee and Cooper 2004, Mabee et al. 2006, Clemson University Radar Ornithology Lab
[CUROL] 2007). Results from the vertical distribution of radar targets in this study and those
from other published studies indicate that the majority of nocturnal migrants fly below 600 m agl
(Bellrose 1971; Gauthreaux 1972, 1978, 1991; Bruderer and Steidinger 1972; Cooper and
Ritchie 1995, Kerlinger 1995).
Similar to nocturnal migration studies elsewhere in Alaska (Cooper et al. 1991; Cooper and
Ritchie 1995; Day et al. 2005; Day et al. 2011; Shook et al. 2001), large among-night variation in
mean flight altitudes occurred during the 2013 migrationsampling for this study. Daily variation
in mean flight altitudes may have reflected changes in species composition, vertical structure of
the atmosphere, and/or weather conditions. Variation among days in the flight altitudes of
migrants at other locations has been associated primarily with changes in the vertical structure of
the atmosphere. For example, birds crossing the Gulf of Mexico appear to fly at altitudes where
favorable winds minimize the energetic cost of migration (Gauthreaux 1991). Kerlinger and
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Moore (1989), Bruderer et al. (1995), and Liechti et al. (2000) have concluded that atmospheric
structure is the primary selective force determining the height at which migrating birds fly.
Diurnal mean spring and fall flight altitudes of all radar targets in this study (350 ± 8.1, 240
±11.6 m agl, respectively) were higher than those reported at Eva Creek (250 ± 14.2, 197 ± 17.0
m agl; Shook et al. 2011). Mean altitudes of passerines (57 m agl) and cranes (576 m agl) and
other groups with intermediate flight altitudes were reported from spring and fall seasons in Tok,
Alaska (Cooper and Ritchie 1995). Direct comparisons with Cooper and Ritchie (1995),
however, are hindered by the differences in radars (i.e., 5 kW units with a parabolic antenna used
by them versus 12kW units with a slotted array antenna used in all other studies).
Nocturnal mean spring flight altitudes of all birds in this study (451 ± 3.6, m agl, respectively)
were higher than those reported at Eva Creek (403 ± 6.0 m agl; Shook et al. 2011) and
potentially lower than those from Delta Junction (478 ± 17.8; Parrett and Day 2009), although
only five nights were sampled during their study. Mean altitudes (146–184 m agl) also were
reported during two years of spring migration in Tok, Alaska (Cooper et al. 1991), but direct
comparisons with this study are hindered by the differences in radar equipment (see above).
Nocturnal mean fall flight altitudes of all birds in this study (403 ± 3.3, m agl, respectively) were
lower than those reported at Eva Creek (432 ± 4.8 m agl; Shook et al. 2011). Mean altitudes
(341–426 m agl) also were reported during two years of spring migration in Tok, Alaska (Cooper
et al. 1991); but direct comparisons with this study are hindered by the differences in radar
equipment. Comparisons at a continental scale suggest that migratory flight altitudes in Alaska
are within the range of those reported in areas to the south (Johnston et al. 2013). A lack of
additional studies for comparison in this region highlights the general lack of information on
nocturnal migration rates in Alaska and the western U.S. and warrants the cautious interpretation
of comparisons with the few studies that are available.
6.1.2.6. Conclusions
The 2013 radar and visual surveys of bird movements in the vicinity of the Watana Dam site are
the most comprehensive migration surveys ever conducted for the Upper Susitna River Basin.
Radar survey results indicated that moderate numbers of nocturnal migrants flew over the study
area in predicted seasonally-appropriate directions during both spring and fall. Visual survey
results suggest that spring migration rates in the basin for waterbirds and cranes are lower than
those recorded elsewhere in central Alaska, particularly those in the Tanana River Valley, north
of the Alaska Range. Fall numbers for all non-passerine groups except cranes were significantly
lower than were spring numbers, and also were lower (including cranes) than have been reported
for fall migration elsewhere in the region. Spring shorebirds were the only group with high
numbers of individuals observed relative to most other studies.
Through the data collection efforts in 2013, the study team is on track to meet the objectives
stated in the Study Plan (RSP Section 10.15.1) for this multi-year study to “[d]ocument the
occurrence, distribution, abundance, habitat use, and seasonal timing of waterbirds migrating
through the Project area in spring and fall.” Swans were undercounted to some extent during the
spring survey because of low visibility during the day with the highest number of (audio)
detections for the season. The record-setting extension of winter weather into May 2013 delayed
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the anticipated onset of migration in the region, but it is unclear to what extent it also may have
affected migratory pathways and passage rates over the Project. What is clear is that arrival dates
of spring migrants to the study area in 2013 were likely to have been much later than in most
other years. It is likely that the survey periods encompassed the vast majority of migration for
most species groups, although water bodies remained open through the end of the survey period
on October 15; so it is possible that some swan migration may have occurred after sampling
ended. Radar and visual surveys confirmed that flight directions of most species groups were
strongly oriented in the directions expected for each season (westerly in spring and easterly in
fall), except for easterly movements of scoter flocks in late May. Radar results indicated
moderate numbers of nocturnal migrants that matched patterns in the seasonal timing of diurnal
radar passage rates and visual movement rates of passerines.
6.2. Breeding Season
The data collected in 2013 during aerial surveys for breeding and brood-rearing waterbirds,
including Harlequin Ducks, met the study objectives to document the occurrence, distribution,
abundance, productivity, and habitat use of waterbirds breeding in the Project area.
6.2.1. Breeding Population Surveys
The first waterbird breeding population survey (June 1-5) appeared to be timed appropriately to
describe the breeding distribution of dabbling ducks in the study area. Large aggregations of
migrants were not observed, and pairs and lone males were dispersed widely across the study
area. The first breeding survey also appeared to capture likely nesting areas for goldeneyes and
grebes. Some mergansers and scoters may not have been present in their nesting locations during
the first week of June, but the first survey was likely the most appropriate for those species as
well due to the reduction of occupied water bodies for mergansers, and the early stages of
grouping and decline in the number of occupied water bodies for scoters during the second
survey. The second breeding waterbird survey (June 14-17) seemed to best identify breeding
areas for scaup, Long-tailed Ducks, and Bufflehead. Swans and loons appeared to occupy known
or likely breeding areas during both surveys. The highest numbers for a given species often
occurred not during the survey when birds were dispersed into nesting areas, but rather when
they were grouped and most conspicuous (i.e. prior to dispersal into nesting areas or after
initiation of nests and departure of males from nesting areas). However, because the counts of
grouped birds may have contained migrants from outside the study area, they did not necessarily
provide the most accurate estimates of the local breeding population.
USFWS conducts an annual waterfowl breeding population survey in early June in an area
adjacent to the transect block from this study east of the Oshetna River (hereafter transect block),
using similar methods. The most recent published data from their survey is from 2011 (Nelchina
Stratum in Mallek and Groves 2011). During that survey, American Wigeon occurred at the
highest density of all waterfowl, followed by Mallards and Green-winged Teal. In the transect
block, Mallards, scaup and Ring-necked Ducks occurred at similar densities during the first
survey, and scaup were by far the most abundant species during the second survey. Compared to
the USFWS survey (Nelchina Stratum), lower densities of most dabbling ducks were observed in
the transect block, including Mallards, American Wigeon, Green-winged Teal and Northern
Pintail. Higher densities of scaup, Northern Shovelers and Long-tailed Ducks were observed in
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the transect block; and similar densities (on at least one of two surveys) of Ring-necked Ducks,
scoters, mergansers and swans. Bufflehead density in the transect block was lower than reported
for the Nelchina Stratum in the first survey, and higher during the second survey. Because the
transect block covers a smaller area and likely occurs in a more uniform habitat than the broader
USFWS survey, it is not surprising to see differences in relative abundance and density of
species between the two surveys. Data compared here were collected in different years; a more
appropriate comparison will be possible when 2013 data from the Nelchina Stratum of the
USFWS surveys become available.
6.2.2. Harlequin Duck Surveys
Harlequin Ducks form pair bonds on the wintering grounds and the pairs return together to
traditional breeding areas (Robertson et al. 1998). During the courtship period, males and
females are visible on breeding streams and defend an area where they forage and conduct
courtship activities (Robertson and Goudie 1999). The Project area is supports a large number of
Harlequin Ducks during the spring, pre-nesting and brood-rearing seasons. The Susitna River
provides good staging habitat in spring when numerous leads in the river ice allow Harlequin
Ducks a place to feed in clear-flowing waters (prior to the muddy waters of river breakup) and a
place to rest on exposed gravel bars or shore fast river ice. Over 500 ducks were recorded on the
Susitna River on May 23–24 and they were distributed all along the river within the study area.
As the amount of open water increased on nearby streams, Harlequin Ducks moved to occupy
breeding territories on them. By the May 28–29 spring survey, the number of Harlequin Ducks
on the Susitna River had dropped to 87 ducks. At other inland breeding areas in North America,
Harlequin Ducks also stage on large rivers before occupying breeding streams (Smith 1998 in
Robertson and Goudie 1999).
The occurrence of spring migration surveys at an interval of every 5–6 days documented the
importance of the Susitna River to Harlequin Ducks as a staging location prior to nesting. The
first pre-nesting survey occurred on June 1–5, just three days after the last spring migration
survey. This date of the first pre-nesting survey was changed from that stated in the Study Plan
because of late river breakup in 2013. By June 1–5, most Harlequin Ducks had moved from the
Susitna River to tributaries and therefore, the first pre-nesting survey was well-timed to
document the use of tributaries for pre-nesting activities. Some of the larger tributaries of the
Susitna and Nenana rivers, like Deadman and Brushkana creeks, may have served as secondary
staging locations for Harlequin Ducks at the time of June 1–5 survey because pairs were grouped
closely together on some streams on that survey. By the time of the June 14–17 survey,
Harlequin Ducks occupied more streams than on the first pre-nesting survey and locations of
pairs were distributed more evenly on streams. The locations of Harlequin Ducks on this survey
may have been a better representation of breeding territories on some streams. Because of a
difference across the study area in the timing of suitable stretches of open water on streams, there
is variation in when Harlequin Ducks can occupy breeding territories on tributaries. The two pre-
nesting surveys conducted in 2013 in the Project area effectively covered the window of time
that pairs are visible on breeding streams.
Streams in the Watana Reservoir and the Denali Corridor survey areas supported the highest
number of pre-nesting Harlequin Ducks in the study area. Greater than ten ducks were found on
the Susitna, Black, Oshetna, and Jack rivers, and Kosina, Goose, Watana, R21, Deadman,
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Brushkana, Tsusena, and Fog creeks. Although most Harlequin Ducks were in pairs on June 14-
17, the high number of sightings of females and males outside of pairs on that survey compared
to the first pre-nesting survey may mean that the process of nest site selection had begun for
some ducks. Only female Harlequin Ducks select the nest site, although males may accompany
female to prospective locations (Robertson and Goudie 1999). Males have been documented to
wait at the confluence of larger watersheds while females select a nest site along a smaller
tributary. The extent of a stream defended by a pair during the pre-nesting period is variable.
Some breeding Harlequin Ducks defend a stretch of stream no greater than 2 mi while other pairs
use twice that much or more (Kuchel 1977, Cassirer and Groves 1992 in Robertson and
Goudie1999). Also, Harlequin Ducks may forage and court on one part of a stream and nest on
another. In Alberta, pre-nesting females were recorded foraging 5 mi downstream from nesting
sites (MacCallum and Bugera 1998 in Robertson and Goudie 1999) and a nesting female was
documented to fly 9 mi from the nest site to a feeding site during incubation breaks (Smith 1999
in Robertson and Goudie 1999). The discovery of a Harlequin Duck nest during the Landbird
and Shorebird Study (Study 10.16) on a very small tributary of Watana Creek indicates that
Harlequin Ducks similarly may nest at sites far from main tributaries where most of their
courting and foraging activities take place.
The dates of the first brood-rearing survey (August 1–5) was determined based on the date of the
discovery of a Harlequin Duck nest in the Project area and the timing of the presence of
Harlequin Ducks on tributaries during pre-nesting. The timing was later than that stated in the
Study Plan, which was based on the assumption of an earlier seasonal phenology. Most broods
were an average age of 12 days old on the August 1–5 brood-rearing survey, which was an age
where they could be detected on rivers with females. If the survey had been conducted any
earlier, the detection of broods probably would have been very low because young broods are
very secretive. Broods on the second brood-rearing survey on August 14–18 were an average of
26 days old. The range in age on that survey was 8–34 days old, which includes broods that
hatched since the first brood-rearing survey. More than twice as many broods were seen on the
second survey (27 broods) as the first survey (12), and between the two surveys at least 30
individual broods were found in the study area. On both surveys, most broods were found in the
Watana Reservoir survey area. The stream with the highest number of broods was Devil Creek
with 4 broods, followed by Goose, Deadman, and Seattle creeks, which had three each. Some
broods probably were missed on each survey because challenging survey conditions (i.e., dense
vegetation and glare) obscured them or made them harder to detect. The use of two brood
surveys helped to detect ducks that were missed on one or the other survey, however, and
effectively covered the window of time in which broods were visible on breeding streams.
6.2.3. Brood Surveys
The two brood surveys conducted in the waterbird brood study area successfully documented the
species composition of waterbirds breeding in the study area. Broods were found for at least 24
of the 38 species recorded in the study area. The dates of the first and second brood survey were
changed from those stated in the Study Plan because of the delay in the availability of open water
and snow-free ground in the study area in 2013. The study team selected the survey dates of the
first brood survey based on the dates when ducks were observed on breeding water bodies and
the presence of female ducks during the breeding population surveys. The timing of the first
survey on July 20–22 successfully documented the start of the nesting season for ducks and the
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August 1–5 survey documented the end of the nesting season. The older broods found on the first
brood survey were ducks that started nesting early, most of which were dabbling ducks
(Northern Pintail, Mallard, and American Wigeon). Scaup were the latest-nesting ducks and
were the most abundant species in the waterbird brood study area. There was a lot of overlap in
the age of broods between dabbling and diving ducks and whether that is a result of the delayed
spring is uncertain. The presence of open water at breeding water bodies varied throughout the
study area during late spring and some areas were suitable for nesting earlier than other areas,
which may also be a reason for the variation in brood ages within a species and between species.
The results of brood surveys in 2013 are not directly comparable with survey results from the
APA project in the 1980s because the two survey areas differed substantially in size; the exact
water bodies surveyed for broods in the 1980s is not known. Brood densities in the 2013
waterbird brood study area were 2.5 to 4 times higher than those reported by Kessel et al. (1982).
However, only 28 water bodies were surveyed in 1981, compared with 499 in 2013. Long-tailed
Duck and Black Scoters were reported as the most productive waterfowl in 1981 on those 28
water bodies (Kessel et al. 1982). During surveys in 2013, scaup were the most productive
waterbird species, followed by goldeneyes, Green-winged Teal, and American Wigeon.
6.3. Information for Mercury Study
A literature review on the diet of waterbirds identified seven species of waterbirds (Common
Loon, Red-throated Loon, Red-necked Grebe, Common Merganser, Red-breasted Merganser,
Bonaparte’s Gull, and Arctic Tern) in the study area as piscivorous waterbirds, for which fish
composed 40 percent or more of their diets. During aerial surveys for waterbirds, numerous lakes
in the study area were occupied by piscivorous waterbirds, but an active nest was found only for
one pair of Common Loons. The nest was on an island in a large lake in the Fog Lakes area and
could not be inspected for feather samples because it occurred on CIRWG lands.
Fewer nests of piscivorous waterbirds were found than expected during aerial surveys in 2013.
The study objective for obtaining tissue samples of piscivorous waterbirds for analysis of
mercury levels was based on opportunistically finding nests. Common Loons on nests are the
most easily detected nesting bird of the seven piscivorous species, but some nests in the study
area probably were missed because waterbird aerial surveys conducted in 2013 focused on
locating and counting birds on the water and did not focus on surveying the lake shorelines
where loons nest. Also, based on the chick ages of Common Loon broods found during brood
surveys, most Common Loons probably did not occupy nests until after the second breeding
survey in mid-June.
Broods of all seven piscivorous species of waterbirds were found during brood and fall migration
surveys in 2013. For Common Loon, Red-throated Loon, Red-necked Grebe, Bonaparte’s Gull,
and Arctic Tern, nesting probably occurred on the same lake where the brood was observed.
These lakes where broods of Common Loon, Red-throated Loon, Red-necked Grebe,
Bonaparte’s Gull, and Arctic Tern were observed, and any additional lakes where only adults
were observed should be surveyed in the next study season for nesting birds. A survey that
specifically targets these nesting birds and is timed to detect birds on nests would be more
effective in meeting the study objectives than relying on finding nests opportunistically.
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7. COMPLETING THE STUDY
[As explained in the cover letter to this draft ISR, AEA’s plan for completing this study will be
included in the final ISR filed with FERC on June 3, 2014.]
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9. TABLES
Table 4.1-1. Details of Aerial Surveys for Migrating and Breeding Waterbirds, 2013.
Target Species Purpose Survey Date Method
Waterbirds Spring Migration April 23 Lake-to-Lake
Waterbirds Spring Migration April 29 Lake-to-Lake
Waterbirds Spring Migration May 5 Lake-to-Lake
Waterbirds Spring Migration May 11 Lake-to-Lake
Waterbirds Spring Migration May 18–19 Lake-to-Lake
Waterbirds Spring Migration May 23–24 Lake-to-Lake
Waterbirds Spring Migration May 28–29 Lake-to-Lake
Waterbirds Breeding June 1–5 Lake-to-Lake
Waterbirds Breeding June 2 Transect
Harlequin Duck Pre-nesting June 1–5 Stream
Waterbirds Breeding June 14–17 Lake-to-Lake
Waterbirds Breeding June 15 Transect
Harlequin Duck Pre-nesting June 14–17 Stream
Waterbirds Brood-rearing July 20–22 Lake-to-Lake
Waterbirds Brood-rearing August 1–5 Lake-to-Lake
Harlequin Duck Brood-rearing August 1–5 Stream
Harlequin Duck Brood-rearing August 14–18 Stream
Waterbirds Fall Migration August 14–18 Lake-to-Lake
Waterbirds Fall Migration August 23–25 Lake-to-Lake
Waterbirds Fall Migration August 29–30 Lake-to-Lake
Waterbirds Fall Migration September 4-6 Lake-to-Lake
Waterbirds Fall Migration September 10–12 Lake-to-Lake
Waterbirds Fall Migration September 16–18 Lake-to-Lake
Waterbirds Fall Migration September 22–23 Lake-to-Lake
Waterbirds Fall Migration September 27–29 Lake-to-Lake
Waterbirds Fall Migration October 4-6 Lake-to-Lake
Waterbirds Fall Migration October 10–12 Lake-to-Lake
Waterbirds Fall Migration October 17–18 Lake-to-Lake
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Table 5.1-1. Status of Waterbird Species Observed during Waterbird Migration and Breeding Surveys, 2013.
SPECIES-GROUP SPECIES-SUBGROUP Common Name Scientific Name Status
WATERFOWL
GEESE
Greater White-fronted Goose1 Anser albifrons Migrant
Snow Goose1 Chen caerulescens Migrant
Canada Goose1 Branta canadensis Migrant
SWANS
Trumpeter Swan1, Cygnus buccinator Confirmed Breeder
Tundra Swan2 Cygnus columbianus Migrant
DABBLING DUCKS
Gadwall1 Anas strepera Confirmed Breeder
American Wigeon1 Anas americana Confirmed Breeder
Mallard1 Anas platyrhynchos Confirmed Breeder
Northern Shoveler1 Anas clypeata Confirmed Breeder
Northern Pintail1 Anas acuta Confirmed Breeder
Green-winged Teal1 Anas crecca Confirmed Breeder
DIVING DUCKS
Canvasback1 Aythya valisineria Migrant
Redhead1 Aythya americana Migrant
Ring-necked Duck1 Aythya collaris Confirmed Breeder
Greater Scaup1, Aythya marila Confirmed Breeder
Lesser Scaup1, Aythya affinis Confirmed Breeder
Harlequin Duck1 Histrionicus histrionicus Confirmed Breeder
Surf Scoter1 Melanitta perspicillata Confirmed Breeder
White-winged Scoter1 Melanitta fusca Confirmed Breeder
Black Scoter1 Melanitta nigra Confirmed Breeder
Long-tailed Duck1 Clangula hyemalis Confirmed Breeder
Bufflehead Bucephala albeola Confirmed Breeder
Common Goldeneye1, Bucephala clangula Possible Breeder
Barrow’s Goldeneye Bucephalai slandica Confirmed Breeder
Common Merganser Mergus merganser Confirmed Breeder
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SPECIES-GROUP
SPECIES-SUBGROUP Common Name Scientific Name Status
Red-breasted Merganser Mergus serrator Confirmed Breeder
LOONS
Red-throated Loon1 Gavia stellata Confirmed Breeder
Pacific Loon Gavia pacifica Confirmed Breeder
Common Loon Gavia immer Confirmed Breeder
Yellow-billed Loon Gavia adamsii Migrant
GREBES
Horned Grebe1 Podiceps auritus Confirmed Breeder
Red-necked Grebe Podiceps grisegena Confirmed Breeder
CRANES
Sandhill Crane Grus canadensis Migrant
GULLS
Bonaparte’s Gull Chroicocephalus philadelphia Confirmed Breeder
Mew Gull Larus canus Confirmed Breeder
Herring Gull Larus argentatus Possible Breeder
TERNS
Arctic Tern Sterna paradisaea Confirmed Breeder
JAEGERS
Long-tailed Jaeger2 Stercorarius longicaudus Possible Breeder
1 Waterbirds identified as species of conservation and management concern in the Wildlife Data-Gap Analysis for
the Proposed Susitna–Watana Hydroelectric Project (ABR 2011).
2 Presence and identification confirmed on ground-based migration surveys.
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Table 5.1-2. Numbers of Waterbirds Observed on Streams and Water Bodies during Spring and Fall Migration Surveys, 2013.
Survey Area/
Feature Location
April May August September October
221 292
5 11 18–19 23–24 28–29 14–18 23–25 29–30 4–6 10–12 16–18 22–23 27–29 4–6 10–12 17–18
Dam/Camp Area
Stream
Tsusena Creek – 0
0 0 0 0 7 – – – – – – – – – – –
Water Body
Fog Lakes3 0 0 0 0 0 0 0 15 8 8 5 3 7 6 7 2 0 0
Unnamed Water Bodies 0 0
0 0 0 0 22 1 8 6 6 6 6 16 5 11 0 3
Dam/Camp Area Total 0 0 0 0 0 0 29 16 16 14 11 9 13 22 12 13 0 3
Watana Reservoir
Stream
Susitna River 0 –
0 249 390 374 131 – – – – – – – – – – –
Watana Creek 0 –
0 2 0 0 16 – – – – – – – – – – –
Kosina Creek 0 –
4 5 0 3 7 – – – – – – – – – – –
Oshetna River – –
0 0 4 0 5 – – – – – – – – – – –
Gilbert Creek – –
0 0 0 0 2 – – – – – – – – – – –
Stream Subtotal 0 – 4 256 394 377 161 – – – – – – – – – – –
Water Body
Fog Lakes3 0 0 0 0 32 95 231 344 168 372 303 259 279 115 172 173 24 66
Clarence Lake 0 – 2 5 12 48 113 129 66 152 133 197 148 167 118 91 6 22
Pistol Lake4 0 – 0 9 – 73 52 47 23 39 38 38 54 5 2 15 0 0
Sally Lake 0 – 0 0 0 44 34 2 1 0 0 0 0 0 1 0 2 0
Watana Lake 0 – 0 0 0 2 5 18 24 18 40 14 28 73 75 61 0 0
Molar Lake 0 0 0 0 0 0 0 62 69 40 50 54 53 38 24 11 0 0
Unnamed Water Bodies 0 0 0 0 0 110 221 338 194 196 202 252 348 80 89 98 10 12
Water Body Subtotal 0 0 2 14 44 356 666 940 545 817 766 814 910 478 481 449 42 100
Watana Reservoir Total 0 0 6 270 438 733 817 940 545 817 766 814 910 478 481 449 42 100
Denali Corridor
Stream
Nenana River – 8
18 106 110 66 109 – – – – – – – – – – –
Brushkana Creek – 0
0 14 25 48 43 – – – – – – – – – – –
Seattle Creek – –
2 0 2 38 3 – – – – – – – – – – –
Deadman Creek – 0
0 0 0 0 62 – – – – – – – – – – –
Jack River – 0
0 0 0 2 3 – – – – – – – – – – –
Stream Subtotal – 8 20 120 137 154 220 – – – – – – – – – – –
Water Body
Lake 1294 (NE of Drashner Lake) – 0 0 223 235 270 175 0 47 110 27 54 14 0 0 0 0 0
Deadman Lake – 1 2 18 4 6 0 40 58 73 53 87 77 48 67 2 0 2
Big Lake 0 0 0 0 0 0 0 27 33 17 10 14 30 28 13 165 43 7
Unnamed Water Bodies – 0 0 0 0 150 332 1,388 1,103 1074 905 1023 691 191 210 209 4 22
Water Body Subtotal – 1 2 241 239 426 507 1,455 1,241 1274 995 1178 812 267 290 376 47 31
Denali Corridor Total – 9 22 361 376 580 727 1,455 1,241 1274 995 1178 812 267 290 376 47 31
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Survey Area/
Feature Location
April May August September October
221 292
5 11 18–19 23–24 28–29 14–18 23–25 29–30 4–6 10–12 16–18 22–23 27–29 4–6 10–12 17–18
Chulitna Corridor
Stream
Indian River 0 0
21 20 0 15 4 – – – – – – – – – – –
Portage Creek 0 0
2 2 0 10 11 – – – – – – – – – – –
Devil Creek 0 –
0 0 0 4 5 – – – – – – – – – – –
Stream Subtotal 0 0 23 22 0 29 20 – – – – – – – – – – –
Water Body
Indian River Beaver Ponds 3 20 17 13 38 34 37 8 0 0 4 4 1 2 0 0 0 3
High Lake 0 0 0 0 0 0 0 0 9 3 6 3 4 0 0 0 0 0
Miami Lake 0 0 0 0 0 0 0 1 7 0 5 12 4 1 0 2 30 24
Swimming Bear Lake 0 0 0 0 0 0 0 12 11 5 11 24 3 0 0 2 0 0
Unnamed Water Bodies 0 2 0 0 0 4 33 141 100 127 104 121 78 68 5 25 9 6
Water Body Subtotal 3 20 17 13 38 38 70 162 127 135 130 164 90 71 5 29 39 33
Chulitna Corridor Total 3 20 40 35 38 67 90 162 127 135 130 164 90 71 5 29 39 33
Gold Creek Corridor
Stream
Susitna River 0 0
7 220 244 702 44 – – – – – – – – – – –
Stephan-Murder Connection 4 8
18 0 4 0 0 – – – – – – – – – – –
Fog Creek 0 0
0 0 0 3 13 – – – – – – – – – – –
Indian River 0 0
0 0 0 2 1 – – – – – – – – – – –
Stream Subtotal 4 8 25 220 248 707 58 – – – – – – – – – – –
Water Body
Murder Lake 0 0 4 84 43 122 144 0 38 116 12 78 103 240 284 116 37 35
Stephan Lake 0 0 6 49 72 72 108 153 62 114 109 112 183 229 378 382 339 303
Lakes North of Stephan Lake 0 0 1 1 12 11 62 46 52 77 91 78 89 94 105 141 50 26
Fog Lakes3 0 0 0 2 0 4 23 32 26 37 46 38 16 8 11 23 2 15
Unnamed Water Bodies 0 0 0 0 0 3 32 159 125 159 85 78 64 40 37 62 5 3
Water Body Subtotal 0 0 11 136 127 212 369 390 303 503 343 384 455 611 815 724 433 382
Gold Creek Corridor Total 4 8 36 356 375 919 427 390 303 503 343 384 455 611 815 724 433 382
All Survey Areas
Total Number on Streams 4 16
72 618 779 1,267 466 – – – – – – – – – – –
Total Number on Water Bodies 3 21 32 404 448 1,032 1,624 2,963 2,232 2,743 2,245 2,549 2,280 1,449 1,603 1,591 561 549
Total All Survey Areas 7 37 104 1,022 1,227 2,299 2,090 2,963 2,232 2,743 2,245 2,549 2,280 1,449 1,603 1,591 561 549
1 The northern part of the Denali Corridor was not surveyed because of inclement weather.
2 The eastern part of the Watana Reservoir was not surveyed because of inclement weather.
3 Fog Lakes are part of three survey areas: Dam/Camp Area, Watana Reservoir, and Gold Creek Corridor.
4 Pistol Lake was not surveyed on May18–19.
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Table 5.1-3. Numbers and Occurrence of Waterbirds during Migration and Breeding Surveys, 2013.
Spring Migration1 Breeding1 Fall Migration1
April May June August September October
Species 23 29
5 11 18–19 23–24 28–29
1–5 14–17
14–18 23–25 29–30
4–6 10–12 16–18 22–23 27–29
4–6 10–12 17–18
Trumpeter Swan 2 12
30 38 51 52 52
53 87
86 67 93
80 68 78 50 57
45 24 14
Unidentified swan2
6 12 20
10
10 14 21 76 69
65
Mallard 2 12
9 155 200 183 108
154 124
222 138 169
145 137 117 105 209
331 86 131
Unidentified goldeneye 2 6
9 64 88 158 95
186 201
183 117 165
132 159 148 165 181
328 97 72
Common Merganser 1 2
5 14 26 20 23
0 2
8 19
7
Bufflehead
5
14 14 42 114 33
63 113
25 36 27
28 41 58 43 43
51 53 26
Northern Pintail
26 163 152 263 151
109 121
192 93 219
100 152 138 25 49
56
26
Northern Shoveler
9 70 69 111 66
85 95
64 16 35
38 28 33 1
3 20
Mew Gull
2 109 13 28 46
3
1
American Wigeon
180 177 217 165
162 196
336 359 351
306 394 298 159 234
150 15 29
Green-winged Teal
114 48 122 114
86 132
324 184 139
124 337 270 4 32
32 4 11
Unidentified teal 43 15 7
Unidentified dabbler 8 77 30 8 31
Canada Goose
14 12 21 3
4
Ring-necked Duck
14 42 48 62
142 42
118 95 98
45 42 77 49 15
44 20 2
Unidentified duck 11 33 48 18 65 62 13 7 29 1 1
Bonaparte's Gull
3
4 7
2
2
Harlequin Duck
2 20 553 186
Unidentified scaup
124 190 662
1,080 761
1,006 787 1,080
1,021 953 892 622 580
418 97 188
Red-breasted Merganser
5 54 30
15 18
33 52 61
39 40 27 10 28
14 1 2
Unidentified merganser
15 17 3
1 0
3
22
7 36 3
4 53
Redhead
4
Canvasback
2
4
Snow Goose3
80 10
15
Herring Gull
9 3
2
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Spring Migration1 Breeding1 Fall Migration1
April May June August September October
Species 23 29
5 11 18–19 23–24 28–29
1–5 14–17
14–18 23–25 29–30
4–6 10–12 16–18 22–23 27–29
4–6 10–12 17–18
Unidentified gull
24 1
2
1
Horned Grebe
6 4
8 1
2
1
4 4 4 1 4
4
3
Long-tailed Duck
101
58 53
85 73 67
57 44 27 10 11
9
Surf Scoter
73
75 72
77 35 87
49 72 29 38 39
4 29 12
White-winged Scoter
63
64 26
18 8 15
18 17 20 13 12
13 9 24
Unidentified scotr 1 2 7 10 1
Red-throated Loon
8
14 10
8 8 6
1 2 2
Common Loon
3
22 21
24 24 25
13 18 11 1 3
3
2
Red-necked Grebe
1
9
5 18 1
1 6 1
4 3
Unidentified grebe 5 2 12
Unidentified diver 4 2 1 2 1 2
Yellow-billed Loon
1
Greater White-fronted
Goose
4
1
Gadwall
2
Black Scoter
14 22
12 10 26
12 11 8 9 15
16 49
Pacific Loon
11 13
19 8 21
12 9 5 2
1
1
Arctic Tern
21
2
Sandhill Crane
16
Number of Birds 7 37 104 1,022 1,227 2,379 2,100 2,443 2,133 2,963 2,232 2,743 2,245 2,549 2,280 1,449 1,603 1,591 561 547
Number of Species 4 5 8 14 17 19 26 26 21 26 20 20 22 20 20 18 17 18 14 16
1 Blank cells indicate no birds observed; intentionally left blank for easy recognition of the occurrence of species in the study area.
2 Some unidentified swans may have been Tundra Swans because groups were observed during spring and fall on the ground-based migration study.
3 Snow Geese observed on May 23–24 and 28–29 were in flight over the Oshetna River area.
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Table 5.1-4. Numbers of Waterbirds by Species-group Observed on Streams and Water Bodies during Spring and Fall Migration Surveys, 2013.
Survey Area Species-Group
Spring Fall
April May August September October 231 292 5 11 18–19 23–24 28–29 14–18 23–25 29–30 4–6 10–12 16–18 22–23 27–29 4–6 10–12 17–18 Dam/Camp Area
Geese 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Swans 0 0 0 0 0 0 0 2 2 0 0 0 2 0 0 0 0 0
Ducks 0 0 0 0 0 0 29 13 12 8 9 9 11 22 12 13 0 3
Loons 0 0 0 0 0 0 0 1 2 6 2 0 0 0 0 0 0 0
Grebes 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Cranes 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Gulls/Terns 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Subtotal 0 0 0 0 0 0 29 16 16 14 11 9 13 22 12 13 0 3
Watana Reservoir
Geese 0 0 0 4 0 0 0 1 0 0 0 0 0 0 0 0 0 0
Swans 0 0 2 14 15 23 15 19 10 8 12 8 16 12 21 8 5 3
Ducks3 0 0 4 208 422 676 783 895 524 788 746 797 888 466 454 436 36 95
Loons 0 0 0 0 0 0 1 15 6 14 4 4 4 0 3 2 0 0
Grebes 0 0 0 0 0 5 1 7 5 7 4 5 2 0 3 3 1 2
Cranes 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Gulls/Terns 0 0 0 44 1 29 17 3 0 0 0 0 0 0 0 0 0 0
Subtotal 0 0 6 270 438 733 817 940 545 817 766 814 910 478 481 449 42 100
Denali Corridor
Geese 0 0 0 10 7 19 3 0 0 0 0 0 0 0 0 0 0 0
Swans 0 1 13 18 30 35 27 40 47 57 46 45 47 28 24 30 4 7
Ducks4 0 8 9 300 333 512 664 1,407 1,172 1,211 949 1,126 762 239 249 346 43 22
Loons 0 0 0 0 0 0 6 5 11 6 0 5 2 0 0 0 0 0
Grebes 0 0 0 0 0 0 2 1 11 0 0 2 0 0 1 0 0 2
Cranes 0 0 0 0 0 0 0 0 0 0 0 0 0 0 16 0 0 0
Gulls/Terns 0 0 0 33 6 14 25 2 0 0 0 0 0 0 0 0 0 0
Subtotal 0 9 22 361 376 580 727 1,455 1,241 1,274 995 1,178 811 267 290 376 47 31
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Survey Area
Species-Group
Spring Fall
April May August September October 231 292 5 11 18–19 23–24 28–29 14–18 23–25 29–30 4–6 10–12 16–18 22–23 27–29 4–6 10–12 17–18 Chulitna Corridor
Geese 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Swans 0 5 8 0 2 4 3 5 4 4 7 2 2 2 2 6 0 0
Ducks 3 15 32 35 36 62 83 148 112 124 115 149 82 67 3 22 39 31
Loons 0 0 0 0 0 0 0 9 11 7 8 11 6 2 0 1 0 2
Grebes 0 0 0 0 0 1 1 0 0 0 0 2 0 0 0 0 0 0
Cranes 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Gulls/Terns 0 0 0 0 0 0 3 0 0 0 0 0 0 0 0 0 0 0
Subtotal 3 20 40 35 38 67 90 162 127 135 130 164 90 71 5 29 39 33
Gold Creek Corridor
Geese 0 0 0 0 5 2 0 0 0 0 0 0 0 0 0 0 0 0
Swans 2 6 7 12 16 10 7 20 14 24 25 27 32 84 79 66 15 4
Ducks 2 2 27 309 348 885 402 339 275 453 304 347 414 524 736 656 415 375
Loons 0 0 0 0 0 0 5 21 10 19 12 9 6 1 0 1 0 1
Grebes 0 0 0 0 0 0 1 4 4 7 1 1 3 1 0 1 3 2
Cranes 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
Gulls/Terns 0 0 2 35 6 22 12 6 0 0 1 0 0 1 0 0 0 0
Subtotal 4 8 36 356 375 919 427 390 303 503 343 384 455 611 815 724 433 382
All Survey Areas
Geese 0 0 0 14 12 21 3 1 0 0 0 0 0 0 0 0 0 0
Swans 2 12 30 44 63 72 52 86 77 93 90 82 99 126 126 110 24 14
Ducks 5 25 72 852 1,139 2,135 1,961 2,802 2,091 2,584 2,121 2,427 2,156 1,318 1,453 1,473 533 524
Loons 0 0 0 0 0 0 12 51 40 52 26 29 18 3 3 4 0 3
Grebes 0 0 0 0 0 6 5 12 20 14 5 10 5 1 4 4 4 6
Cranes 0 0 0 0 0 0 0 0 0 0 0 0 0 0 16 0 0 0
Gulls/Terns 0 0 2 112 13 65 57 11 0 0 1 0 0 1 0 0 0 0
Total Number 7 37 104 1,022 1,227 2,379 2,100 2,963 2,232 2,743 2,245 2,549 2,280 1,449 1,603 1,591 561 549
1 The northern part of the Denali Corridor was not surveyed because of inclement weather.
2 The eastern part of the Watana Reservoir was not surveyed because of inclement weather.
3 Includes 11 observations of unidentified divers which could have been diving ducks, loons, or grebes.
4 Includes 1 observation of an unidentified diver which could have been a diving duck, loon, or grebe.
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Table 5-1-5. Seasonal Population Statistics for Water Bodies Surveyed during Spring and Fall Migration Surveys, 1980–1981 and 2013.
Spring 19811 Fall 19801 Spring 2013 Fall 2013
Water Bodies2 Size (mi2) Mean no. birds
Mean
density (no./mi2) Mean no. species Mean no. birds
Mean
density (no./mi2) Mean no. species Mean no. birds
Mean
density (no./mi2) Mean no. Species Mean no. birds
Mean
density (no./mi2) Mean no. species
WB 107 0.06 51.3 876.0 5.0 39.0 665.9 4.3 60.1 931.8 5.3 96.3
1,644.3 4.5
(Murder Lake)
WB 106 1.38 99.7 72.2 7.3 156.0 112.9 9.5 35.4 29.7 4.6 214.2 155.1 8.8
(Stephan Lake)
WB 145 0.58
54.7 93.6 7.0 103.8 177.6 7.0 28.3 48.4 2.9 111.7 191.1 5.7
(Clarence Lake)
WB 059 0.58 21.3 36.4 4.7 72.8 124.5 6.5 18.7 32.0 1.4 123.4 211.0 6.3
(in Fog Lake group)
WB 0673 0.343 85.0 250.5 6.0 19.0 40.5 4.0 16.9 49.7 2.4 26.9 57.4 3.0
(Pistol Lake)
WB 1054 0.21 4.4 20.9 1.9 40.8 192.2 4.8
(near Stephan Lake)
WB 1304 0.62 2.1 3.4 0.9 46.1 74.2 2.6
(Deadman Lake)
WB 0604 0.43 7.1 16.7 1.3 55.8 130.3 5.6
(in Fog Lake group)
WB 148 0.48 21.3 44.6 3.0 95.8 200.5 3.8 0.7 1.5 0.3 31.0 64.9 4.3
(Watana Lake)
1 Data from APA Susitna Hydroelectric Project study (Kessel et al. 1982).
2 Water body designations follow Kessel et al. 1982.
3 Includes water bodies 064–067 for fall 1980 and fall 2013 analyses (water body size = 0.47 mi²). Statistics are based on this lake grouping for fall surveys
only.
4 Population statistics not available for 1980–1981 surveys.
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Table 5.1-6. Importance Ranks and Values of Water Bodies Surveyed for Waterbirds during Spring and Fall Migration Surveys, 1980–1981 and 2013.
Importance Rank1 (Value2)
Water Bodies3 Survey Area Spring 19814 Fall 19804 Spring 2013 Fall 2013
WB 107 (Murder Lake) Gold Creek Corridor 1 (21.5) 1 (19.7) 1 (136.3) 1 (63.9)
WB 106 (Stephan Lake) Gold Creek Corridor 3 (9.0) 2 (18.7) 2 (43.7) 2 (41.3)
WB 145 (Clarence Lake) Watana Reservoir 4 (7.7) 3 (15.0) 3 (34.9) 4 (26.3)
WB 059 (in Fog Lake group) Watana Reservoir 8 (3.8) 4 (12.7) 5 (19.8) 3 (29.0)
WB 067 (Pistol Lake) Denali Corridor 2 (11.9) 9 5 (6.0) 4 (24.7) 115 (10.0)
WB 105 (near Stephan Lake) Gold Creek Corridor 10 (3.5) 6 (10.3) 6 (12.6) 6 (17.0)
WB 130 (Deadman Lake) Denali Corridor 6 (4.3) 7 (7.0) 8 (6.6) 10 (11.1)
WB 060 (in Fog Lake group) Watana Reservoir 9 (3.8) 13 (1.8) 7 (11.2) 5 (18.1)
WB 148 (Watana Lake) Watana Reservoir 11 (3.0) 5 (12.0) 11 (1.8) 9 (11.5)
1 Rank of importance value within the season. Includes water bodies that were among the six highest importance
value ratings in at least one season. For 1980 and 1981, rankings are restricted to the lakes also surveyed in
2013.
2 Single metric combining abundance, density, and species diversity to describe relative use (“importance”) of
water bodies by birds (see text for equation). Importance values are relative to a specific dataset and cannot be
compared among seasons or analyses.
3 Water body designations follow Kessel et al. 1982.
4 Importance values were approximated from figures in Kessel et al. 1982.
5 Includes water bodies 064–067, which were grouped for the fall analyses (“Pistol Lake Group”).
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Table 5.1-7. Distributions of Radar Targets Observed between 1.5 km and 6.0 km on 6-km-range Surveillance Radar.
Diurnal Nocturnal
Season Minimum distance (m)
Transect crossed Transect crossed
North South North South
Spring n = 71 n = 77 n = 236 n = 212
1,501–2,000 45.1% 41.6% 45.8% 39.6%
2,001–2,500 21.1% 13.0% 25.8% 20.3%
2,501–3,000 18.3% 11.7% 7.6% 9.4%
3,001–3,500 8.5% 13.0% 5.5% 10.4%
3,501–4,000 2.8% 13.0% 6.4% 8.5%
4,001–4,500 2.8% 3.9% 3.0% 6.6%
4,501–5,000 1.4% 2.6% 3.0% 2.4%
5,001–5,500 0.0% 1.3% 2.5% 2.8%
5,501–6,000 0.0% 0.0% 0.4% 0.0%
Fall n = 13 n = 30 n = 96 n = 156
1,501–2,000 61.5% 43.3% 72.9% 67.3%
2,001–2,500 30.8% 13.3% 11.5% 13.5%
2,501–3,000 0.0% 23.3% 8.3% 3.2%
3,001–3,500 7.7% 13.3% 3.1% 4.5%
3,501–4,000 0.0% 0.0% 2.1% 8.3%
4,001–4,500 0.0% 3.3% 0.0% 0.6%
4,501–5,000 0.0% 3.3% 0.0% 0.0%
5,001–5,500 0.0% 0.0% 1.0% 1.9%
5,501–6,000 0.0% 0.0% 1.0% 0.6%
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Table 5.1-8. Flight Altitudes of Targets Observed on 1.5-km Vertical Radar.
Spring Fall
Survey period Flight altitude (m agl) n Category%
Cumulative % n Category%
Cumulative %
Diurnal 1–100 310 22.5 22.5 88 28.1 28.1
101–200 249 18.1 40.7 76 24.3 52.4
201–300 208 15.1 55.8 67 21.4 73.8
301–400 160 11.6 67.4 33 10.5 84.3
401–500 99 7.2 74.6 15 4.8 89.1
501–600 81 5.9 80.5 15 4.8 93.9
601–700 80 5.8 86.3 4 1.3 95.2
701–800 36 2.6 88.9 3 1.0 96.2
801–900 39 2.8 91.8 6 1.9 98.1
901–1,000 48 3.5 95.3 4 1.3 99.4
1,001–1,100 35 2.5 97.8 1 0.3 99.7
1,101–1,200 13 0.9 98.8 1 0.3 100.0
1,201–1,300 7 0.5 99.3 0 0.0 100.0
1,301–1,400 9 0.7 99.9 0 0.0 100.0
1,401–1,500 1 0.1 100.0 0 0.0 100.0
Total 1,375 313
Nocturnal 1–100 592 9.0 9.0 863 12.1 12.1
101–200 893 13.5 22.5 1,119 15.7 27.9
201–300 914 13.8 36.3 1,077 15.1 43.0
301–400 893 13.5 49.8 912 12.8 55.8
401–500 777 11.8 61.6 886 12.5 68.3
501–600 693 10.5 72.1 691 9.7 78.0
601–700 583 8.8 80.9 542 7.6 85.6
701–800 398 6.0 86.9 370 5.2 90.8
801–900 304 4.6 91.5 253 3.6 94.4
901–1,000 224 3.4 94.9 147 2.1 96.4
1,001–1,100 118 1.8 96.7 88 1.2 97.7
1,101–1,200 100 1.5 98.2 79 1.1 98.8
1,201–1,300 76 1.2 99.3 48 0.7 99.5
1,301–1,400 31 0.5 99.8 30 0.4 99.9
1,401–1,500 12 0.2 100.0 9 0.1 100.0
Total 6,608 7,114
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Table 5.1-9. Seasonal Movement Rates and Movement Patterns of Species Groups Observed North and South of the Visual Observation Station during Diurnal Visual Survey Periods.
Season/Avian Group
Mean ± SE daily movement rates
(birds/h)
Flocks observed crossing north or south transects
All distances1 Within 1.5 km of station2
n Percent crossing north transect
Percent crossing south transect n Crossing north transect (N of canyon) Crossing south transect (over Susitna River canyon)
Spring
Swans 1.80 ± 0.71 51
33.3 66.7
41 34.1 65.9
Other waterfowl 2.31 ± 0.61 139 36.0 64.0 77 28.6 71.4
Loons 0.03 ± 0.01 20 40.0 60.0 10 40.0 60.0
Bald Eagle 0.14 ± 0.02 47 14.9 85.1 24 12.5 87.5
Golden Eagle 0.15 ± 0.02 73 20.5 79.5 41 22.0 78.0
Unidentified eagles 0.03 ± 0.01 9 11.1 88.9 3 0.0 100.0
Other raptors 0.37 ± 0.05 148 30.4 69.6 103 36.9 63.1
Cranes 0.03 ± 0.02 11 9.1 90.9 7 14.3 85.7
Shorebirds 1.82 ± 0.93 119 51.3 48.7 88 52.3 47.7
Larids 0.46 ± 0.14 82 50.0 50.0 50 48.0 52.0
Ravens 0.13 ± 0.02 39 33.3 66.7 27 37.0 63.0
Other passerines 4.00 ± 0.95 617 51.1 48.9 458 53.5 46.5
Unknown/other birds 0.02 ± 0.01 6 16.7 83.3 3 66.7 33.3
Spring Total 11.30 ± 2.06 1,361 42.2 57.8 932 44.8 55.2
Fall
Swans 0.52 ± 0.20 25 44.0 56.0 16 56.3 43.8
Other waterfowl 0.12 ± 0.09 6 50.0 50.0 2 50.0 50.0
Loons 0.01 ± 0.01 2 50.0 50.0 1 100.0 0.0
Bald Eagle 0.06 ± 0.02 24 45.8 54.2 13 30.8 69.2
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Season/Avian Group
Mean ± SE daily movement rates
(birds/h)
Flocks observed crossing north or south transects
All distances1 Within 1.5 km of station2
n Percent crossing
north transect
Percent crossing
south transect n Crossing north
transect (N of canyon)
Crossing south transect
(over Susitna River canyon)
Golden Eagle 0.02 ± 0.01 13 15.4 84.6 7 28.6 71.4
Fall (continued)
Other raptors 0.18 ± 0.03 65 27.7 72.3 45 33.3 66.7
Cranes 2.86 ± 2.52 26 50.0 50.0 5 20.0 80.0
Shorebirds 0.00 0 -- -- 0 -- --
Larids 0.01 ± 0.01 2 50.0 50.0 0 -- --
Ravens 0.33 ± 0.08 56 58.9 41.1 44 59.1 40.9
Other passerines 5.31 ± 0.73 255 33.7 66.3 224 37.1 62.9
Unknown/other birds 0.01 ± 0.01 1 0.0 100.0 0 -- --
Fall Total 9.43 ± 2.56 476 37.6 62.4 358 39.7 60.3
1 Includes all non-local movements with extrapolated flight paths that cross the north or south cardinal transects.
2 Includes all non-local movements with flight paths that cross the north or south cardinal transects within 1.5 km of visual observation station.
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Table 5.1-10. Post-sunset Audio-visual Observations of Birds (Number of Flocks) Detected Using Binoculars and Night-vision Goggles during Spring 2013.
Species-group1 Common Name
Week Starting
Apr 20 Apr 27 May 4 May 11 May 18 May 25 June 1 Total2
Waterfowl 1 2 7 0 17 46 3 76 (31/45)
Unidentified geese 1 1 2 (2/0)
Tundra Swan 2 1 3 (1/2)
Mallard 1 1 (1/0)
Northern Shoveler 1 1 (0/1)
White-winged Scoter 1 1 (0/1)
Unidentified scoters 3 3 (1/2)
Red-breasted Merganser 1 1 (1/0)
Unidentified ducks 1 3 9 39 3 55 (24/31)
Unidentified waterfowl 1 7 1 9 (1/8)
Loons 0 0 0 0 0 1 0 1 (1/0)
Unidentified loons 1 1 (1/0)
Raptors 0 0 1 1 2 4 0 8 (6/2)
Peregrine Falcon 1 1 2 (1/1)
Short-eared Owl 1 2 3 6 (5/1)
Shorebirds 0 0 0 0 16 25 1 42 (18/24)
Pectoral Sandpiper 2 2 (0/2)
Long-billed Dowitcher 1 1 (1/0)
Wilson’s Snipe 9 23 1 33 (13/20)
Unidentified shorebirds 4 2 6 (4/2)
Larids 0 0 0 0 0 2 0 2 (1/1)
Herring Gull 1 1 (1/0)
Unidentified gulls 1 1 (0/1)
Passerines 0 0 2 5 25 20 2 54 (39/15)
Swainson’s Thrush 5 5 (1/4)
American Robin 1 2 4 7 (6/1)
Varied Thrush 1 1 (0/1)
Unidentified thrushes 5 1 6 (5/1)
White-crowned Sparrow 1 1 (1/0)
Unidentified passerines 1 3 14 15 1 34 (26/8)
Total spring flocks 1 2 10 6 60 98 6 183 (96/87)
1 Numbers in bold are subtotals of individual species within species-groups.
2 Numbers in parentheses are numbers of flocks seen during first hour post-sunset compared to number of flocks
seen during later hours of the night.
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Table 5.1-11. Post-sunset Audio-visual Observations of Birds (Number of Flocks) Detected Using Binoculars and Night-vision Goggles during Fall 2013.
Species-group1 Common Name
Week Starting
Aug 16 Aug 23 Aug 30 Sep 6 Sep 13 Sep 20 Sep 27 Oct 4 Oct 11 Total2
Waterfowl 0 0 0 0 0 0 0 1 0 1 (0/1) Unidentified swans 1 1 (0/1)
Shorebirds 0 0 1 0 0 0 0 0 0 1 (1/0) Wilson’s Snipe 1 1 (1/0)
Passerines 3 28 1 7 3 0 0 0 0 42 (2/40) Unidentified passerines 3 28 1 7 3 42 (2/40)
Total fall flocks 3 28 2 7 3 0 0 1 0 44 (3/41)
1 Numbers in bold are subtotals of individual species within species-groups.
2 Numbers in parentheses are numbers of flocks seen during the first hour post-sunset compared to number of flocks seen during later hours of the night.
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Table 5.2-1. Mean Density of Waterfowl Observed during Breeding Surveys in Breeding Lake Groups, 2013.
Survey Area Breeding Lake Group
No. of Birds Density (birds/mi2)
Water Body Area Surveyed (mi2)
June 1–5 June 14–17 June 1–5 June 14–17 June 1–5 June 14–17
Dam/Camp Area
Fog Lakes1 9 4 278.7 97.4 0.03 0.04
Lower Tsusena2 58 29
181.7 92.8
0.32 0.31
Dam/Camp Area Total 67 33
190.6 93.3
0.35 0.35
Watana Reservoir
Clarence Lake Area 71 128
109.3 197.0
0.65 0.65
East Lower Watana 32 10
293.5 91.7
0.11 0.11
East Upper Watana 23 17
426.0 327.9
0.05 0.05
Fog Lakes1 402 370
232.0 214.3
1.73 1.73
Goose 55 32
370.4 225.0
0.15 0.14
Molar Lake 18 104
52.0 300.5
0.35 0.35
North Kosina 58 51
562.8 493.4
0.10 0.10
Oshetna 76 67
206.4 182.0
0.37 0.37
Pistol Lake3 193 54
395.1 112.8
0.49 0.48
South Kosina 12 17
275.4 254.0
0.04 0.07
Watana Lake 16 22
33.5 46.0
0.48 0.48
Watana Mt 11 14
291.0 383.5
0.04 0.04
West Lower Watana 59 21
667.3 237.5
0.09 0.09
West Upper Watana 15 8
389.9 210.1
0.04 0.04
Watana Reservoir Total 1,041 915
222.2 195.4
4.69 4.68
Denali Corridor
Big Lake 7 24
4.3 14.6
1.64 1.64
Brushkana 139 165
308.9 436.3
0.45 0.38
Deadman East 40 –
276.8 –
0.14 –
Deadman Lake 42 37
64.2 56.9
0.65 0.65
Deadman North 0 9
0.0 243.3
0.04 0.04
Deadman Pass 102 68
828.2 1,038.0
0.12 0.07
Deadman South 24 42
127.9 171.7
0.19 0.24
Deadman West 60 44
732.2 589.3
0.08 0.07
Lower Big Lake 8 20
59.9 149.8
0.13 0.13
Nenana East 127 210
643.1 1,063.4
0.20 0.20
Nenana West 223 175
689.4 526.7
0.32 0.33
Pistol Lake3 2 3 19.3 28.9 0.10 0.10
Upper Tsusena4 51 – 2,341.6 – 0.02 –
Denali Corridor Total 825 797
201.1 206.5
4.10 3.86
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Survey Area Breeding Lake Group
No. of Birds Density (birds/mi2)
Water Body Area Surveyed (mi2)
June 1–5 June 14–17 June 1–5 June 14–17 June 1–5 June 14–17
Chulitna Corridor
Devil North 23 27
31.0 40.4
0.74 0.67
Indian5 63 35
107.2 58.9
0.59 0.59
Lower Tsusena2 18 5
1,527.7 424.3
0.01 0.01
Miami Lake 3 1
13.9 4.6
0.22 0.22
Portage6 19 24
24.5 28.9
0.78 0.83
Upper Tsusena4 2 2
4.5 4.5
0.44 0.44
Chulitna Corridor Total 128 94
46.1 34.0
2.77 2.76
Gold Creek Corridor
Devil North 4 4 449.9 449.9 0.01 0.01
Devil South 5 8
36.5 57.3
0.14 0.14
Fog Lakes1 25 3 31.8 29.4 0.79 0.78
Indian5 11 2 159.8 30.8 0.07 0.06
Lake Group 10 7 –
203.2 –
0.03 –
Lake Group 14 9 –
125.1 –
0.07 –
Lake Group 146 5 3 66.7 33.9 0.07 0.09
Murder Lake 73 4
1,246.5 68.3
0.06 0.06
Portage6 44 25 51.4 31.3 0.86 0.80
Stephan Lake 157 146
113.5 105.6
1.38 1.38
Stephan North 42 79
58.6 110.2
0.72 0.72
Gold Creek Corridor Total 382 294
91.0 72.7
4.20 4.04
Total All Survey Areas 2,443 2,133
151.7 135.8
16.11 15.70
1 Fog Lakes breeding lake group was divided between three survey areas: Dam/Camp Area, Watana Reservoir,
and Gold Creek Corridor.
2 Lower Tsusena breeding lake group was divided between two survey areas: Dam/Camp Area and Chulitna
Corridor.
3 Pistol Lake breeding lake group was divided between two survey areas: Watana Reservoir and Denali Corridor.
4 Upper Tsusena breeding lake group was divided between two survey areas: Denali and Chulitna corridors
5 Indian breeding lake group was divided between two survey areas: Chulitna and Gold Creek corridors.
6 Portage breeding lake group was divided between two survey areas: Chulitna and Gold Creek corridors.
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Table 5.2-2. Number and Density1 (birds/mi²) of Waterfowl Observed during Breeding Surveys of Water Bodies, 2013.
Dam/Camp Area2 Watana Reservoir2 Denali Corridor2 Chulitna Corridor2 Gold Creek Corridor2 Total Density2
Species June 1–5 June 14–17 June 1–5 June 14–17 June 1–5 June 14–17 June 1–5 June 14–17 June 1–5 June 14–17 June 1–5 June 14–17
Greater White-fronted Goose 0 (0) 0 (0) 0 (0) 0 (0) 1 (0.2) 0 (0) 0 (0) 0 (0) 3 (0.7) 0 (0) 4 (0.2) 0 (0)
Snow Goose 0 (0) 0 (0) 15 (3.2) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 15 (0.9) 0 (0)
Canada Goose 1 (2.8) 0 (0) 2 (0.4) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 1 (0.2) 0 (0) 4 (0.2) 0 (0)
Trumpeter Swan 2 (5.7) 2 (5.7) 11 (2.3) 12 (2.6) 29 (7.1) 49 (12.7) 0 (0) 2 (0.7) 11 (2.6) 22 (5.4) 53 (3.3) 87 (5.5)
Gadwall 0 (0) 0 (0) 0 (0) 0 (0) 2 (0.5) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 2 (0.1) 0 (0)
American Wigeon 5 (14.2) 1 (2.8) 62 (13.2) 32 (6.8) 57 (13.9) 136 (35.2) 13 (4.7) 1 (0.4) 25 (6.0) 26 (6.4) 162 (10.1) 196 (12.6)
Mallard 8 (22.8) 0 (0) 43 (9.2) 41 (8.8) 55 (13.4) 58 (15.0) 33 (11.9) 5 (1.8) 15 (3.6) 20 (4.9) 154 (9.6) 124 (7.9)
Northern Shoveler 0 (0) (5.6) 51 (10.9) 29 (6.2) 24 (5.8) 55 (14.2) 4 (1.4) 0 (0) 6 (1.4) 9 (2.2) 85 (5.3) 95 (6.0)
Northern Pintail 0 (0) 0 (0) 26 (5.5) 57 (12.2) 70 (17.1) 57 (14.8) 6 (2.2) 0 (0) 7 (1.7) 7 (1.7) 109 (6.8) 121 (7.7)
Green-winged Teal 2 (5.7) 0 (0) 22 (4.7) 72 (15.4) 39 (9.5) 41(10.6) 6 (2.2) 0 (0) 17 (4.1) 19 (4.7) 86 (5.3) 132 (8.4)
Canvasback 0 (0) 0 (0) 1 (0.2) 0 (0) 3 (0.7) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 4 (0.2) 0 (0)
Ring-necked Duck 9 (25.6) 4 (11.3) 67 (14.3) 22 (4.7) 40 (9.8) 14 (3.6) 4 (1.4) 0 (0) 22 (5.2) 2 (0.5) 142 (8.8) 42 (2.7)
Unidentified scaup 17 (48.4) 13 (36.8) 478 (102.0) 304 (64.9) 375 (91.4) 279 (72.3) 37 (13.3) 45 (16.3) 173 (41.2) 120 (29.7) 1,080 (67.0) 761 (48.5)
Surf Scoter 6 (17.1) 0 (0) 49 (10.5) 61 (13.0) 8 (1.9) 4 (1.0) 0 (0) 0 (0) 12 (2.9) 7 (1.7) 75 (4.7) 72 (4.6)
White-winged Scoter 0 (0) 0 (0) 56 (11.9) 26 (5.6) 0 (0) 0 (0) 2 (0.7) 0 (0) 6 (1.4) 0 (0) 64 (4.0) 26 (1.7)
Black Scoter 0 (0) 0 (0) 5 (1.1) 17 (3.6) 6 (1.5) 0 (0) 0 (0) 0 (0) 3 (0.7) 5 (1.2) 14 (0.9) 22 (1.4)
Unidentified scoter 0 (0) 0 (0) 1 (0.2) 1 (0.2) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 1 (0.2) 1 (0.1) 2 (0.1)
Long-tailed Duck 0 (0) 5 (14.1) 19 (4.0) 23 (4.9) 31 (7.6) 18 (4.7) 1 (0.4) 6 (2.2) 7 (1.7) 1 (0.2) 58 (3.6) 53 (3.4)
Bufflehead 7 (19.9) 3 (8.5) 18 (3.8) 62 (13.2) 27 (6.6) 24 (6.2) 2 (0.7) 16 (5.8) 9 (2.1) 8 (2.0) 63 (3.9) 113 (7.2)
Common Goldeneye 0 (0) 0 (0) 1 (0.2) 0 (0) 0 (0) 0 (0) 3 (1.1) 0 (0) 0 (0) 0 (0) 4 (0.2) 0 (0)
Barrow’s Goldeneye 4 (11.4) 0 (0) 53 (11.3) 0 (0) 7 (1.7) 0 (0) 10 (3.6) 0 (0) 30 (7.2) 0 (0) 104 (6.5) 0 (0)
Unidentified goldeneye 1 (2.8) 0 (0) 36 (7.7) 137 (29.2) 27 (6.6) 27 (7.0) 0 (0) 12 (4.3) 14 (3.3) 25 (6.2) 78 (4.8) 201 (12.8)
Common Merganser 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 1 (0.3) 0 (0) 0 (0) 0 (0) 1 (0.2) 0 (0) 2 (0.1)
Red-breasted Merganser 0 (0) 0 (0) 0 (0) 5 (1.1) 4 (1.0) 9 (2.3) 2 (0.7) 0 (0) 9 (2.1) 4 (1.0) 15 (0.9) 18 (1.1)
Unidentified merganser 0 (0) 0 (0) 0 (0) 0 (0) 1 (0.2) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 1 (0.1) 0 (0)
Red-throated Loon 0 (0) 0 (0) 2 (0.4) 2 (0.4) 7 (1.7) 2 (0.5) 2 (0.7) 2 (0.7) 3 (0.7) 4 (1.0) 14 (0.9) 10 (0.6)
Pacific Loon 5 (14.2) 3 (8.5) 4 (0.8) 2 (0.4) 1 (0.2) 0 (0) 0 (0) 2 (0.7) 1 (0.2) 6 (1.5) 11 (0.7) 13 (0.8)
Common Loon 0 (0) 0 (0) 9 (1.9) 9 (1.9) 5 (1.2) 2 (0.5) 3 (1.1) 3 (1.1) 5 (1.2) 7 (1.7) 22 (1.4) 21 (1.3)
Horned Grebe 0 (0) 0 (0) 6 (1.3) 1 (0.2) 2 (0.5) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 8 (0.5) 1 (0.1)
Red-necked Grebe 0 (0) 0 (0) 3 (0.6) 0 (0) 3 (0.7) 0 (0) 0 (0) 0 (0) 3 (0.7) 0 (0) 9 (0.7) 0 (0)
Bonaparte’s Gull 0 (0) 0 (0) 1 (0.2) 0 (0) 1 (0.2) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 2 (0.1) 0 (0)
Area (mi²) of Lakes Surveyed 0.3 0.3 4.7 4.7 4.1 3.9 2.8 2.8 4.2 4.0 16.1 15.7
Total Number (Total Density) 67 (190.6) 33 (93.3) 1,041(222.1) 915 (195.4) 825 (201.1) 797 (206.5) 128 (46.1) 94 (34.0) 382 (91.0) 294 (72.7) 2,443(151.7) 2,133(135.8)
1 Density calculated as the number of birds/lake area surveyed in each corridor.
2 Density is presented in parentheses.
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Table 5.2-3. Numbers and Densities of Waterbirds Observed during Breeding-population Transect Surveys, 2013.
Date Species Males1 Pairs Grouped Birds2
Indicated Total No. Birds3
Visibility Correction Factor4
Corrected Total No. Birds5
Density6 (birds/ mi²)
Composition (% of total)
June 2
Snow Goose7 0 0 26 26 1 26 1.4 12
Canada Goose 0 1 0 2 1 2 0.1 1
Trumpeter Swan7 1 5 0 11 1 11 0.6 5
American Wigeon 0 1 0 2 3.65 7 0.4 3
Mallard 2 2 0 8 3.57 29 1.5 13
Northern Shoveler 0 1 0 2 3.35 7 0.3 3
Northern Pintail 1 0 0 2 2.51 5 0.3 2
Green-winged Teal 1 0 0 2 8.88 18 0.9 8
Ring-necked Duck7 3 2 0 7 4.02 28 1.5 13
Unidentified scaup7 4 6 0 16 1.82 29 1.5 14
Surf Scoter 0 6 0 12 1.08 13 0.7 6
Long-tailed Duck 0 1 0 2 1.99 4 0.2 2
Barrow’s Goldeneye 0 2 0 4 3.61 14 0.8 7
Red-throated Loon7 1 2 0 5 3.3 17 0.9 8
Common Loon7 0 3 0 6 1 6 0.3 3
Total 13 32 26 107 216 11.4 100
June 15
Trumpeter Swan7 5 5 0 15 1 15 0.8 4
American Wigeon 2 3 0 10 3.65 37 1.9 10
Mallard 0 1 0 2 3.57 7 0.4 2
Northern Shoveler 2 0 0 4 3.35 13 0.7 4
Ring-necked Duck7 5 0 0 5 4.02 20 1.0 5
Unidentified scaup7 14 22 9 67 1.82 122 6.3 33
Surf Scoter 6 10 6 38 1.08 41 2.1 11
Long-tailed Duck 1 2 0 6 1.99 12 0.6 3
Bufflehead 5 4 0 18 1.86 33 1.7 9
Unidentified goldeneye 0 1 0 2 3.61 7 0.4 2
Red-breasted Merganser 4 4 0 16 1.27 20 1.1 5
Red-throated Loon7 5 1 0 7 3.3 23 1.2 6
Common Loon7 1 0 0 1 1 1 0.1 0
Horned Grebe7 0 2 0 4 5.4 22 1.1 6
Total 50 55 15 195 373 19.4 100
1 Includes single birds of unknown sex for geese, swans, loons, and grebes.
2 Grouped birds are those that occurred in flocks with >4 males and for which no assumptions were made as to
the number of pairs.
3 Indicated Total No. Birds = (number of males in groups [<5 males] x 2) + (number of pairs x 2) + number of
birds in groups.
4 Visibility Correction Factor developed by USFWS (as reported in Mallek and Groves 2011 for most species;
Conant et al. 1991 for loons and grebes).
5 Corrected Total No. Birds = Indicated Total No. Birds x Visibility Correction Factor.
6 Density based on corrected total number of birds in a 19.25-square-mile (mi²) sample area.
7 Males and single birds not doubled in calculating indicated total number of birds.
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Table 5.2-4. Numbers of Harlequin Ducks Observed during Spring Migration Surveys, 2013.
Survey Area Stream May 11 May 18–19 May 23–24 May 28–29
Dam/Camp Area
Tsusena Creek 0 0 0 3
Dam/Camp Area Total 0 0 0 3
Watana Reservoir
Susitna River 0 11 235 67
Kosina Creek 0 0 3 7
Oshetna River 0 0 0 4
Watana Reservoir Total 0 11 238 78
Denali Corridor
Deadman Creek 0 0 0 27
Brushkana Creek 0 0 4 26
Nenana River 0 0 14 6
Seattle Creek 0 0 2 0
Denali Corridor Total 0 0 20 59
Chulitna Corridor
Portage Creek 0 0 4 6
Indian Creek 0 0 2 4
Devil Creek 0 0 0 2
Chulitna Corridor Total 0 0 6 12
Gold Creek Corridor
Susitna River 2 9 286 20
Fog Creek 0 0 3 13
Indian River 0 0 0 1
Gold Creek Corridor Total 2 9 289 34
Outside 3-mile Buffer
Jack River 0 0 1 10
Oshetna River 0 2 0 7
Indian River 0 0 0 4
Gilbert Creek 0 0 0 3
Outside 3-mile Buffer Total 0 2 1 24
Total All Survey Areas 2 22 554 210
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Table 5.2-5. Numbers of Harlequin Ducks Observed during Pre-nesting Surveys, 2013.
June 1–51 June 14–171
Survey Area Stream2
Single Male Single Female Pairs Total Birds3
Single Male Single Female Pairs Total Birds3
Dam/Camp Area
Deadman Creek 2 0 0 2
0 2 0 2
Susitna River 0 0 0 0
0 0 1 2
Tsusena Creek 0 0 0 0
0 0 0 0
Dam/Camp Area Total 2 0 0 2
0 2 1 4
Watana Reservoir
Black River 0 0 0 0
5 6 9 29
Fog Creek 0 0 0 0
1 0 0 1
Gilbert Creek 1 0 2 5
1 1 1 4
Goose Creek 2 0 5 12
0 1 1 3
Jay Creek 0 0 0 0
0 0 4 8
Kosina Creek 1 0 7 15
2 5 5 17
Oshetna River 1 0 5 11
0 1 1 3
R12 0 0 0 0
1 0 1 3
R18 0 0 0 0
0 0 0 0
R19 0 0 0 0
0 0 0 0
R21 0 0 0 0
0 2 4 10
Susitna River 3 0 5 13
1 1 5 12
Tsisi Creek 2 0 4 10
1 2 3 9
Watana Creek 0 0 0 0
4 1 5 15
Watana Reservoir Total 10 0 28 66
16 20 39 114
Denali Corridor
Brushkana Creek 1 1 12 26
0 2 2 6
Deadman Creek 6 2 12 32
4 3 5 17
Jack River 0 0 7 14
0 2 3 8
Nenana River 0 0 0 0
0 0 0 0
Seattle Creek 0 0 1 2
0 0 1 2
Wells Creek 0 0 0 0
0 0 0 0
Denali Corridor Total 7 3 32 74
4 7 11 33
Chulitna Corridor
Clark Creek 0 0 0 0
0 0 0 0
Devil Creek 0 0 1 2
0 1 0 1
Indian River 0 0 2 4
0 0 1 2
Portage Creek 0 1 1 3
0 0 0 0
R9 0 0 0 0
0 0 0 0
Thoroughfare Creek – – – –
0 0 0 0
Tsusena Creek 0 0 1 2
2 1 5 13
Chulitna Corridor Total 0 1 5 11
2 2 6 16
Gold Creek Corridor
Cheechako Creek 0 0 0 0
0 0 0 0
Chinook Creek – – – –
0 0 0 0
Fog Creek 0 0 5 10
0 0 0 0
Gold Creek – – – –
0 0 0 0
Indian River 0 0 0 0
0 1 0 1
Susitna River 0 0 5 10
5 0 6 17
Gold Creek Corridor Total 0 0 10 20
5 1 6 18
Total All Survey Areas 19 4 75 173
27 32 63 185
1 Dashed lines indicate stream was not surveyed.
2 Indian and Susitna rivers and Deadman, Fog, and Tsusena creeks occur in multiple survey areas.
3 Total = (number of single males) + (number of single females) + (number of pairs x 2).
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Table 5.2-6. Numbers of Harlequin Ducks Observed during Brood-rearing Surveys, 2013.
August 1–51 August 14–181
Survey Area
Stream2
Females
Young
Total
Birds
No. Broods
Females
Young
Total
Birds
No. Broods
Dam/Camp Area
Deadman Creek 0 0 0 0 0 0 0 0
Susitna River 0 0 0 0 – – – –
Tsusena Creek 0 0 0 0 0 0 0 0
Dam/Camp Area Total 0 0 0 0 0 0 0 0
Watana Reservoir
Black River 2 4 6
1
1 2 3
1
Fog Creek 0 0 0
0
1 6 7
1
Gilbert Creek 2 4 6
1
3 9 12
2
Goose Creek 2 0 2
0
3 13 16
3
Jay Creek 2 5 7
2
0 0 0
0
Kosina Creek 7 0 7
0
1 0 1
0
Oshetna River 0 0 0
0
3 0 3
0
R12 0 0 0 0 0 0 0 0
R18 – – – – – – – –
R19 – – –
–
1 6 7
1
R21 4 5 9
1
3 9 12
2
Susitna River 0 0 0 0 – – – –
Tsisi Creek 3 0 3
0
0 0 0
0
Watana Creek 5 10 15
2
3 10 13
2
Watana Reservoir Total 27 28 55
7
19 55 74
12
Denali Corridor
Brushkana Creek 5 0 5
0
0 0 0
0
Deadman Creek 5 4 9
1
3 9 12
3
Jack River 3 0 3
0
0 0 0
0
Nenana River – – – – – – – –
Seattle Creek 2 7 9
2
3 8 11
3
Wells Creek – – – – 0 0 0 0
Denali Corridor Total 15 11 26
3
6 17 23
6
Chulitna Corridor
Clark Creek 0 0 0
0
1 4 5
1
Devil Creek 0 0 0
0
4 12 16
4
Indian River 2 11 13
2
3 3 6
1
Portage Creek 1 0 1
0
1 4 5
1
R9 0 0 0 0 0 0 0 0
Thoroughfare Creek 2 0 2
0
0 0 0
0
Tsusena Creek 1 0 1
0
1 5 6
1
Chulitna Corridor Total 6 11 17
2
10 28 38
8
Gold Creek Corridor
Cheechako Creek 0 0 0 0 0 0 0 0
Chinook Creek 0 0 0 0 0 0 0 0
Fog Creek 2 0 2
0
1 6 7
1
Gold Creek 0 0 0 0 0 0 0 0
Indian River 0 0 0 0 0 0 0 0
Susitna River 0 0 0 0 – – – –
Gold Creek Corridor Total 2 0 2
0
1 6 7
1
Total All Survey Areas 50 50 100
12
36 106 142
27
1 Dashed lines indicate stream was not surveyed.
2 Indian and Susitna rivers and Deadman, Fog, and Tsusena creeks occur in multiple survey areas.
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Table 5.2-7. Numbers of Waterbird Broods Observed on Water Bodies during Brood-rearing Surveys, 2013.
Species
Dam/Camp Area Watana Reservoir Denali Corridor Chulitna Corridor Gold Creek Corridor Total Broods
Jul 20–22 Aug 1–5 Jul 20–22 Aug 1–5 Jul 20–22 Aug 1–5 Jul 20–22 Aug 1–5 Jul 20–22 Aug 1–5 Jul 20–22 Aug 1–5
Trumpeter Swan 0 0 0 0 1 2 0 0 0 0 1 2
Gadwall 0 0 0 0 0 0 0 1 0 0 0 1
American Wigeon 0 0 0 0 9 9 0 1 0 0 9 10
Mallard 0 1 2 0 2 0 1 2 1 0 6 3
Northern Shoveler 0 0 0 0 1 1 0 0 0 0 1 1
Northern Pintail 0 0 0 1 3 7 1 0 0 0 4 8
Green-winged Teal 1 0 2 2 12 14 2 0 2 2 19 18
Unidentified dabbler 0 0 0 0 2 1 1 0 0 0 3 1
Ring-necked Duck 0 1 0 0 1 0 0 0 0 0 1 1
Unidentified scaup 0 0 9 9 23 37 0 3 1 7 33 56
Surf Scoter 1 1 0 0 1 1 0 0 3 3 5 5
White-winged Scoter 0 0 1 1 0 0 0 0 0 0 1 1
Black Scoter 0 0 0 0 0 0 1 0 0 0 1 0
Long-tailed Duck 0 0 0 0 4 3 0 0 0 0 4 3
Bufflehead 0 0 0 0 1 1 0 0 0 0 1 1
Unidentified goldeneye 1 2 2 4 2 5 3 11 2 4 10 26
Red-breasted Merganser 0 1 0 0 0 0 0 0 0 0 0 1
Unidentified merganser 0 0 0 0 0 1 0 0 0 0 0 1
Unidentified duck 0 0 0 1 0 0 0 0 0 0 0 1
Red-throated Loon 0 0 0 0 1 0 0 0 0 0 1 0
Pacific Loon 0 0 0 0 0 0 0 0 1 1 1 1
Common Loon 0 0 1 0 0 1 0 1 2 0 3 2
Horned Grebe 0 0 2 1 0 0 0 0 0 0 2 1
Red-necked Grebe 0 0 0 0 0 0 0 0 0 1 0 1
Bonaparte’s Gull 0 0 0 0 1 2 0 0 0 0 1 2
Mew Gull 0 0 0 0 1 3 0 0 0 0 1 3
Unidentified gull 0 0 0 0 2 1 0 0 0 0 2 1
Arctic Tern 0 0 0 0 1 0 0 0 0 0 1 0
Total Broods 3 6 19 19 68 89 9 19 12 18 111 151
Number of Species 3 5 7 6 16 14 5 6 7 6 21 21
Density (broods/mi2) 8.1 16.1 40.7 40.7 30.5 39.9 11.1 23.4 7.0 9.7 19.5 26.3
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Table 5.2-8. Age Subclass1 of Duck Broods Observed during Brood-rearing Surveys, 2013.
July 20–22 August 1–5
Species 1A 1B 1C 2A 2B 2C Brood Total 1A 1B 1C 2A 2B 2C 3 Brood Total
Gadwall 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1
American Wigeon 0 0 4 4 1 0 9 0 0 0 7 2 1 0 10
Mallard 0 2 2 0 2 0 6 0 0 0 1 1 1 0 3
Northern Shoveler 1 0 0 0 0 0 1 0 0 0 0 1 0 0 1
Northern Pintail 0 0 0 0 2 2 4 0 0 0 0 1 6 1 8
Green-winged Teal 5 6 5 2 1 0 19 0 0 3 6 4 5 0 18
Unidentified dabbler 1 1 1 0 0 0 3 0 0 1 0 0 0 0 1
Ring-necked Duck 0 1 0 0 0 0 1 0 0 1 0 0 0 0 1
Unidentified scaup 10 22 1 0 0 0 33 1 9 25 18 3 0 0 56
Surf Scoter 0 4 1 0 0 0 5 0 0 0 5 0 0 0 5
White-winged Scoter 1 0 0 0 0 0 1 0 0 1 0 0 0 0 1
Black Scoter 0 0 0 0 1 0 1 0 0 0 0 0 0 0 0
Long-tailed Duck 0 1 0 3 0 0 4 0 0 1 0 2 0 0 3
Bufflehead 0 0 0 1 0 0 1 0 0 0 0 1 0 0 1
Unidentified goldeneye 3 6 0 1 0 0 10 0 3 1 14 4 4 0 26
Red-breasted Merganser 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1
Unidentified merganser 0 0 0 0 0 0 0 0 0 1 0 0 0 0 1
Unidentified duck 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1
Total 21 43 14 11 7 2 98 1 13 35 52 19 17 1 138
1 Age span for each subclass differs among species; however, for all species, Class 1 chicks are downy and there are no visible feathers. Class 2 chicks are
partially feathered, and Class 3 chicks are fully feathered.
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10. FIGURES
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Figure 3-1. Waterbird Study Area for the Susitna–Watana Hydroelectric Project.
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Figure 4.1-1. Water Bodies Surveyed for Waterbirds during Spring and Fall Migration in the Chulitna and Gold Creek Corridors, 2013.
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Figure 4.1-2. Water Bodies Surveyed for Waterbirds during Spring and Fall Migration in the Reservoir Inundation Zone and Vicinity, 2013.
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Figure 4.1-3. Water Bodies Surveyed for Waterbirds during Spring and Fall Migration in the Denali Corridor, 2013.
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Figure 4.1-4. Radar and Visual Sampling Area for Ground-based Surveys of Migration, 2013.
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Figure 4.1-5. Water Bodies Surveyed for Breeding Waterbirds, and Streams Surveyed for Harlequin Ducks, in the Chulitna and Gold Creek Corridors, 2013.
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Figure 4.1-6. Water Bodies and Transect Lines Surveyed for Breeding Waterbirds, and Streams Surveyed for Harlequin Ducks, in the Reservoir Inundation Zone and Vicinity, 2013.
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Figure 4.1-7. Water Bodies Surveyed for Breeding Waterbirds, and Streams Surveyed for Harlequin Ducks, in the Denali Corridor, 2013.
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Figure 5.1-1. Locations and Maximum Number of Waterbirds Observed on Rivers and Water Bodies during Spring Migration Surveys, 2013. Locations are centerpoints of water bodies and midpoints of sections of river.
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Figure 5.1-2. Locations and Maximum Number of Waterbirds Observed on Water Bodies during Fall Migration Surveys, 2013. Locations are centerpoints of water bodies.
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Figure5.1-3. Spring Diurnal and Nocturnal Passage Rates (mean ± SE) by Date for Targets Detected within the 1.5-km Radar Range. Asterisks indicate that no radar sampling occurred due to weather.
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Figure 5.1-4. Passage Rates (mean ± SE) of Targets, Grouped by Time of Day, during Spring and Fall Migration, for Targets Detected within the 1.5-km Radar Range.
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Figure 5.1-5. Passage Rates (mean ± SE) Relative to Hour Post-Sunset During Spring and Fall Migration, for Targets Detected within the 1.5-km Radar Range.
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Figure 5.1-6. Diurnal and Nocturnal Flight Directions of Targets Detected within the 1.5-km Radar Range.
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Figure 5.1-7. Radar Targets Detected >1.5 km from the Sampling Station during Spring and Fall Migration.
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Figure 5.1-8. Mean Diurnal and Nocturnal Flight Altitudes (m agl) of Targets during Spring Migration, by Date for Targets Detected within the 1.5-km Radar Range. Asterisks (*) indicate that no radar sampling occurred (due to weather), and blanks indicate dates with sample sizes too small (<5 targets) to calculate meaningful values.
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Figure 5.1-9. Mean Flight Altitudes (m agl) of Targets, Grouped by Time of Day, during Spring and Fall Migration for Targets Detected within the 1.5-km Radar Range.
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Figure 5.1-10. Mean Movement Rates (birds/h) of Passerines by Week of the Spring and Fall Migration Survey Seasons.
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Figure 5.1-11. Mean Movement Rates (birds/h) of Waterbirds by Week of the Spring and Fall Migration Survey Seasons.
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Figure 5.1-12. Mean Movement Rates (birds/h) of Raptors by Week of the Spring and Fall Migration Survey Seasons.
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Figure 5.1-13. Mean Movement Rates (birds/h) of Sandhill Cranes by Week of the Spring and Fall Migration Survey Seasons.
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Figure 5.1-14. Mean Movement Rates (birds/h) of Bird Groups by Time of Day during Spring Migration Survey Season.
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Figure 5.1-15. Flight Altitude Categories for Species Groups Observed during Diurnal Visual Surveys in Spring.
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Figure 5.1-16. Ordinal Flight Directions of Bird Flocks Observed during Spring Diurnal Visual Surveys.
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Figure 5.1-17. Fall Diurnal and Nocturnal Passage Rates (targets/km/h) by Date for Targets Detected within the 1.5-km Radar Range. Asterisks indicate that no radar sampling occurred due to weather.
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Figure 5.1-18. Mean Diurnal and Nocturnal Flight Altitudes (m agl) of Targets during Spring Migration, by Date for Targets Detected within the 1.5-km Radar Range. Asterisks (*) indicate that no radar sampling occurred (due to
weather), and blanks indicate dates with sample sizes too small (<5 targets) to calculate meaningful values.
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Figure 5.1-19. Mean Movement Rates (birds/h) of Bird Groups by Time of Day during Fall Migration Survey Season.
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Figure 5.1-20. Flight Altitude Categories for Species Groups Observed during Diurnal Visual Surveys in Fall.
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Figure 5.1-21. Ordinal Flight Directions of Bird Flocks Observed during Fall Diurnal Visual Surveys.
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Figure 5.2-1. Locations of Harlequin Ducks Observed during Spring Migration Surveys, 2013.
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Figure 5.2-2. Locations of Harlequin Duck Observed during Pre-nesting Surveys, 2013.
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Figure 5.2-3. Locations of Harlequin Duck Observed during Brood-rearing Surveys, 2013.
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Figure 5.2-4. Locations and Numbers of Waterbird Broods Observed during Brood-rearing Surveys, 2013.