OCS Study MMS 2005-057 

Final Report 

Importance of the Alaskan Beaufort Sea to King Eiders (Somateria 

spectabilis) 

Principal Investigator: Abby N. Powell, Ph.D. 

Research Associate Professor 

Institute of Arctic Biology 

University of Alaska Fairbanks 

and Research Wildlife Biologist, USGS 

Alaska Cooperative Fish and Wildlife Research Unit 

Co-principal Investigator: Laura Phillips, M. S. 

Dept. Biology and Wildlife 

University of Alaska Fairbanks 

Co-principal Investigator: Eric A. Rexstad, Ph.D. 

Associate Professor 

Institute of Arctic Biology 

University of Alaska Fairbanks 

Co-principal Investigator: Eric J. Taylor, Ph.D. 

Fish and Wildlife Biologist 

U.S. Fish and Wildlife Service 

and Research Associate 

Institute of Arctic Biology 

University of Alaska Fairbanks 

Prepared by Laura Phillips

August 2005
LIST OF TABLES ........................................................................................................................ 3

LIST OF FIGURES ...................................................................................................................... 3

ABSTRACT................................................................................................................................... 5

INTRODUCTION......................................................................................................................... 6

METHODS .................................................................................................................................... 7

Trapping Sites ............................................................................................................................. 7 

Beaufort Sea................................................................................................................................ 7 

Bering Sea................................................................................................................................... 7 

Capture and Telemetry................................................................................................................ 8 

Data Analysis............................................................................................................................ 10 

Distribution and Use Areas .................................................................................................. 10 

Movements............................................................................................................................ 11 

Beaufort Sea Location Characteristics................................................................................. 11 

RESULTS .................................................................................................................................... 12

Distribution and Use Areas....................................................................................................... 12 

Movements................................................................................................................................ 18 

Beaufort Sea Location Characteristics...................................................................................... 21 

DISCUSSION .............................................................................................................................. 24

Distribution and Use Areas....................................................................................................... 24 

Movements................................................................................................................................ 25 

Beaufort Sea Location Characteristics...................................................................................... 25 

ACKNOWLEDGEMENTS ....................................................................................................... 26

STUDY PRODUCTS.................................................................................................................. 27

LITERATURE CITED .............................................................................................................. 28

2
LIST OF TABLES 

Table 1. Definitions of King Eider nonbreeding life history events as defined by satellite 

telemetry locations. ...................................................................................................... 10 

Table 2. Proportion of male and female satellite transmittered king eiders captured on the 

North Slope of Alaska located in major wing molt and wintering areas in 2002 –

2004.............................................................................................................................. 18 

Table 3. Means and ranges of dates of dispersal from breeding areas, arrival at wing molt 

sites, dispersal from wing molt sites, and arrival at subsequent breeding areas for 

60 king eiders captured on the North Slope of Alaska in 2002 – 2004. ...................... 20 

Table 4. Mean (± SE) residence time and date of first location within the Alaskan Beaufort 

Sea of transmittered king eiders during post-breeding (n = 60 eiders) and spring 

migration (n = 24 eiders), June 2002 – September 2004. ............................................ 22 

LIST OF FIGURES 

Figure 1. Post-breeding distributions of king eiders (34 male, 26 female) within the Alaskan 

Beaufort Sea, 2002 – 2004........................................................................................... 13 

Figure 2. Post-breeding and spring distributions of satellite-tagged king eiders in the Alaskan 

Beaufort Sea, June 2002 – September 2004. Distributions include locations from 

60 king eiders during post-breeding and 24 king eiders during spring........................ 14 

Figure 3. Post-breeding distributions within the Alaskan Beaufort Sea of king eiders captured 

at Kuparuk and Teshekpuk Lake on the North Slope of Alaska. Distributions 

include locations from 15 king eiders captured at Kuparuk and 12 king eiders 

captured at Teshekpuk Lake in 2004. .......................................................................... 14 

Figure 4. Staging areas of satellite transmittered king eiders during spring and wing molt 

migration. ..................................................................................................................... 15 

Figure 5. Distribution of 59 satellite transmittered king eiders during 2002 – 2004 wing molt 

periods. Areas occupied by two or more eider locations over the three years of the 

study are outlined by a dashed grey line. ..................................................................... 16 

Figure 6. Distribution of 29 satellite transmittered king eiders during 2002 – 2003 at farthest 

south wintering sites. Areas occupied by two or more eider locations over the two 

years of the study are outlined by a dashed grey line. ................................................. 17 

Figure 7. Mean number of days spent on wing molt migration and at wing molt sites for 

satellite transmittered king eiders for years 2002 – 2004. Sample sizes for the 

number of individual eiders used to calculate mean days of wing molt migration 

and duration at wing molt sites are represented respectively by the italicized 

number before and after the bar graphs. Ranges associated with dates of dispersal 

from breeding areas, arrival at wing molt sites, and dispersal from wing molt sites 

can be found in Table 3................................................................................................ 21 

3
Figure 8. Plot of residence time and standardized date of arrival within the Alaskan Beaufort 

Sea of king eiders (n = 60) during spring and post-breeding periods.......................... 23 

Figure 9. Mean residence time (days, black bar) and range (grey bars) transmittered king 

eiders were located within the Alaskan Beaufort Sea during spring and postbreeding periods........................................................................................................... 23 

4
ABSTRACT 

Alaskan-breeding king eiders (Somateria spectabilis) molt wing feathers and over winter 

in remote areas of the Bering Sea, precluding direct observation. This study employed the use of 

satellite telemetry to determine areas used by king eiders throughout the annual cycle. We 

collected location data of 60 individuals (27 females and 33 males) over three years (2002–2004) 

from satellite telemetry. More than 80% of our transmittered eiders spent more than 2 weeks 

staging offshore prior to beginning molt migration, suggesting that the sea is an important 

migration flyway and staging area for this species. During post-breeding staging and migration, 

male king eiders had much broader distributions in the Alaskan Beaufort Sea than female eiders, 

which were concentrated in Harrison and Smith Bays. Distribution of locations did not vary by 

sex during spring migration. Significant variation in residence time in the Beaufort Sea was 

explained by sex with female king eiders spending more days within the sea than males during 

post-breeding and spring migrations. Shorter residence times of eiders and deeper water depths 

at locations during spring migration suggest the Alaskan Beaufort Sea may not be as critical a 

staging area for king eiders in spring as it is post-breeding. Distributions of molt and winter 

locations did not differ by sex or among years. We recommend managers minimize disturbance 

of core use areas in Harrison and Smith Bays during post-breeding and future studies examine 

the importance of potential spring staging areas outside the Alaskan Beaufort Sea. 

 

5
INTRODUCTION 

King eiders (Somateria spectabilis) spend the majority of their annual cycle in remote 

marine habitats, precluding direct observation and contributing to an incomplete understanding 

of their life histories. King eiders perform wing molt, fall, and spring migrations during the 

nonbreeding period (Suydam 2000), and presumably this migratory behavior has evolved as an 

advantage to provide the greatest potential reproductive success for individuals (Baker 1978). 

This study was developed with two broad objectives: (1) to determine the use of the Beaufort Sea 

as a flyway and staging area, and (2) to provide an initial description of the migration ecology of 

king eiders breeding on Alaska’s North Slope. 

Alaskan-breeding king eiders disperse from nesting areas on the Arctic Coastal Plain and 

move through the Beaufort Sea to wing molt and wintering locations in the Bering Sea. 

Hundreds of thousands of king eiders use the Alaskan Beaufort Sea as a flyway, staging, or 

molting area each year (Thomson and Person 1963, Woodby and Divoky 1982, Suydam et al. 

2000). Development of offshore oil and gas resources on natural and artificial islands in the 

Beaufort Sea has prompted managers to fund baseline studies about the distribution of king 

eiders in the sea. These data are critical to model potential consequences from oil spills and to 

provide regulatory agencies with opportunities to modify proposed developments and associated 

activities to minimize impacts. Potential impacts from oil spills may include displacement of 

eiders from foraging habitat, contamination of food resources, and mortality from oiling (Flint et 

al. 1999, Stehn and Platte 2000). 

After leaving the Beaufort Sea, king eiders migrate to marine areas where they 

congregate in flocks and molt all flight feathers. During this three-to-four week flightless period, 

movements are constrained, and eiders may be vulnerable to disturbance and predation, and 

subject to higher energy demands (Salomonsen 1968, King 1974, Hohman et al. 1992). Postmolting king eiders then migrate to wintering areas that are generally characterized by short 

periods of daylight and extremes in weather conditions, temperature, and ice cover (Systad et al. 

2000, Petersen and Douglas 2004). Eiders generally form pair bonds on these wintering areas 

and migrate as pairs to breeding grounds in the spring (Anderson et al. 1992). 

The chronology of these life-history events during the nonbreeding period may be linked 

to productivity on the breeding grounds (Heitmeyer and Fredrickson 1981, Hepp 1984, Dugger 

1997), and may vary by age, sex, and habitat condition (Heitemeyer 1988). This may be 

especially true for eiders due to their heavy reliance on endogenous reserves for egg laying 

(Korschgen 1977, Kellet 1999). Concern regarding apparent population declines in recent years 

of all four eider species (Stehn et al. 1993, Suydam et al. 2000) has led to increased interest in 

location and timing of migration, definition of wing molt and wintering areas, and habitat 

characterization of these sites (U.S. Fish and Wildlife Service 1999, Sea Duck Joint Venture 

Management Board 2001). 

In this study, we obtained location data for the entire annual cycle of 33 king eiders in 

2002 and 2003. Additionally, we collected wing molt location information for 27 eiders in 2004. 

Thus, we can model the areas of the Alaskan Beaufort Sea used by king eiders during spring 

migration and post-breeding and describe the movements of king eiders throughout the 

nonbreeding period.

The original objectives of this study were to: (1) document movements and locations of 

spring, summer, and fall migrating adult female king eiders (successful and unsuccessful 

breeders) marked on breeding areas on the North Slope of Alaska; (2) describe potential staging 

6
areas used during spring and fall migration; (3) determine if adult female king eiders molt in the 

Beaufort Sea prior to migration to overwintering areas; (4) describe sea ice and open water 

conditions of the Beaufort Sea relative to observed locations of satellite implanted king eiders. 

 Due to logistical limitations on our ability to trap king eiders on breeding grounds in 

summer and the inherent low annual reproductive success of this species, we did not obtain a 

sample of female king eiders that successfully raised young to fledgings. We were also not able 

to obtain information on the nesting status of the females using transmitters prior to egg laying. 

Due to these limitations, we restrict our analyses to only unsuccessful female and male king 

eiders. 

 Satellite imagery of sea ice in the Beaufort Sea was not available at intervals frequent 

enough for useful description of conditions in the Beaufort Sea relative to king eider locations. 

However, we describe water depth and distance offshore of king eider locations within the 

Beaufort Sea and determine explanatory variables that describe variation in the number of days 

king eiders spend within the sea. 

To address the above objectives, we will examine the distribution and use areas of king 

eiders while in the Beaufort Sea, during spring and fall staging, and during wing molt and winter; 

describe the timing of migratory movements; and describe characteristics of king eider locations 

within the Beaufort Sea. 

METHODS 

Trapping Sites 

We trapped king eiders in early to mid-June of 2002, 2003, and 2004 at two sites on the 

North Slope of Alaska, Teshekpuk Lake (70°26'N, 153°08'W) and Kuparuk (70°20'N, 

149°45'W). The Kuparuk study site was located between the Colville and Kuparuk Rivers. The 

Teshekpuk Lake study site was added as a trapping location in 2004 and was located about 80 

km west of the Kuparuk study area and 10 km inland from the southeast shore of Teshekpuk 

Lake. 

Beaufort Sea 

During the post-breeding period (late June through mid-September), Alaskan-breeding 

king eiders move into the Beaufort Sea where they stage or begin migration to wing molt 

locations. The Beaufort Sea is part of the Arctic Ocean that lies north of Alaska from Point 

Barrow eastward to Banks Island north of the Yukon and Northwest Territories of Canada. It 

has a narrow continental shelf that extends an average of 55 km offshore to the 200 m 

bathymetric contours (Soluri and Woodson 1990). Sea ice generally covers the entire sea for 9 

to 10 months each year. Nearshore ice freezes to the seafloor in winter and ice scouring of 

benthic habitats nearshore can be severe (Barnes et al. 1984). Primary productivity is low, and 

food webs are relatively simple with secondary biological productivity peaking during the icefree summer months of June through October (Norton and Weller 1984). 

Bering Sea 

During wing molt migration (late June through mid-September), Alaskan-breeding king 

eiders generally move into the Bering Sea. The Bering Sea is characterized by a large, shallow, 

7
gently-sloping coastal shelf that is less than 200 m deep and encompasses almost half the sea’s 

total area. This shelf is broad in the east (>500 km) along the Alaskan coast and narrow (<100 

km) in the west along the Siberian coast. 

In winter, the Bering Sea is characterized by high winds, frequent storms, and complete 

ice coverage of its shallow continental shelf region (Niebauer et al. 1999). The seasonal ice pack 

persists for six to eight months each year and generally reaches its maximum southern extent by 

March or April (Fay 1974). Major polynyas occur downwind of the Chukchi Peninsula, St. 

Lawrence Island, St. Matthew Island, and the Seward Peninsula (Stringer and Groves 1991). 

The amount of available daylight in the Bering Sea decreases to between four and six hours in 

late December and early January. 

The Bering Sea is unusually productive for a high latitude body of water. A number of 

mechanisms are thought to support this high productivity, including the broad shallow coastal 

shelf, the extensive seasonal ice coverage, and the convergence of current systems rich in 

nutrients (Springer and McRoy 1993). The high density of benthic invertebrates in the Bering 

Sea is thought to be linked to its high primary productivity (Grebmeier 1993). King eiders 

probably forage on benthic and epibenthic invertebrates while in marine systems (Frimer 1997, 

Suydam 2000). 

Capture and Telemetry 

We obtained locations of king eiders throughout the nonbreeding period using 

implantable satellite transmitters. We captured king eiders on breeding grounds in early to midJune using mist net arrays and decoys. Once captured, eiders were placed in a secure, dark 

kennel and transported to an indoor facility or weatherport equipped for surgery. A 35-g satellite 

platform transmitting terminal (PTT) transmitter (Microwave Telemetry, Inc., Columbia, 

Maryland) was surgically implanted into the abdominal cavity of each eider following the 

techniques of Korschgen et al. (1996). Satellite transmitters were <3% of the average body mass 

of birds used in this study. Surgeries generally took 20 minutes to complete. We held birds until 

fully awake and recovered from anesthesia (2 – 3 h), and then released them at their capture 

sites. If both the male and female of a pair were captured simultaneously, we released the pair 

together at the capture site. At Kuparuk, transmitters were implanted into 21 (10 female, 11 

male) king eiders in 2002, 12 (3 female, 9 male) in 2003, and 15 (8 female, 7 male) in 2004. We 

fitted 12 (5 female, 7 male) king eiders with transmitters at Teshekpuk in 2004. Eiders were 

fitted with a U.S. Fish and Wildlife Service band while still under anesthesia. All methods and 

handling of birds were approved by the University of Alaska Institutional Animal Care and Use 

Committee (IACUC # 02-10). There were no fatalities within three months of surgery. 

To maximize location and duration of wing molt and location duration and timing of molt 

migration, transmitters were programmed with four duty cycles. Transmitters were on and 

transmitting location information to satellites for six hours every 48 h from June through 

September, every 84 h from October through December, every 168 h from January through 

March, and every 84 h from April until the end of the battery life. The expected battery life was 

about one year. Satellite transmitters used in this study had an average life-span of 385 ± 15 

(SE) days (n = 33, range 99 – 519 days). We received location data from Service Argos (2001). 

Error associated with satellite telemetry locations has been estimated by Service Argos (2001) to 

be < 1km for locations with a location class of at least 0 and < 150 m for locations with a class of 

3; however, a study by Britten et al. (1999) estimated an average error of 4 km for 0 class 

8
locations from small (30g) backpack-mounted satellite transmitters. There is no published 

information on the accuracy of the 35g implantable satellite transmitters used in this study. 

Location data was filtered for accuracy using PC-SAS Argos Filter V6.4 (Dave Douglas, USGS, 

Alaska Science Center, Anchorage, AK). The filtering program removed implausible locations 

based on location redundancy and tracking paths. For our analyses, the best location per 

transmission period was used based on location class to ensure independence of locations. 

Locations were plotted using ArcView GIS (ESRI 1998). Definitions used to categorize events 

throughout the annual cycle for use in analyses are included in Table 1. 

 

9
Table 1. Definitions of King Eider nonbreeding life history events as defined by satellite 

telemetry locations.

Definition 

Migration A set of sequential locations indicating movement in a single direction during 

which an individual remains in one area > 1 week (Petersen et al. 1999) 

Wing molt 

migration 

The migration period from the last day at the breeding area to the first day at 

the wing molt location 

Wing molt site An area where an eider spent > 3 weeks with lowest daily movement rates 

between June and December prior to movement toward wintering areas 

Fall migration The migration period from the last day at the wing molt site to the first day at 

the farthest south wintering location 

Wintering area An area where an eider spent > 1 week between the end of the wing molt 

period and spring migration; King Eiders may have multiple wintering areas 

Spring 

migration 

 

The period of migration from the last day at a wintering area to the first day on 

land at a subsequent breeding location; if there were no onshore locations for 

an eider during the subsequent breeding period, the first location at a June 

offshore staging area was used 

Subsequent 

breeding area 

An area onshore where an individual was located after spring migration and 

prior to fall migration 

Data Analysis 

Distribution and Use Areas 

Beaufort Sea. We used fixed kernel analysis (Seaman et al. 1998) to delineate king eider 

use areas in the Beaufort Sea. We considered the 95% utilization distribution to represent an 

estimate of total distribution, and the contour representing greater than average observed density 

as the core use area. Due to the variation in the number of locations obtained per individual in 

the Alaskan Beaufort Sea (range: 1 – 44 locations), we randomly selected a subset of locations 

based on the average number of locations received per individual within a season to ensure 

kernel distributions reflected the distribution of our sample of individuals rather than any one 

individual eider. We randomly selected 10 post-breeding locations (June – September) and 7 

spring locations (April – July) per individual to create 2 subsets of eider locations for use in 

kernel analyses. 

10
Differences in distributions of king eider locations in the Beaufort Sea were examined 

using multiresponse permutation procedures (MRPP) in BLOSSOM (USGS, Fort Collins, 

Colorado; Cade and Richards 2001). We examined differences by sex and season (spring vs. 

post-breeding), and among years. We also compared 2004 post-breeding distributions of male 

and female king eiders transmittered at Kuparuk to those captured at Teshekpuk. Because 

MRPP is sensitive to large differences in sample sizes, we randomly selected a subset of 

locations from larger samples when necessary to make sample sizes equivalent. 

Post-breeding and spring staging. Staging areas of king eiders during wing molt and 

spring migrations were described. Spring staging areas were defined as areas where eiders spent 

> 1 week during spring migration, and post-breeding staging areas were defined as areas where 

king eiders spent > 1 week during wing molt migration.

Wing molt and winter. Latitudes of wing molt and wintering sites were calculated as the 

centroid of minimum convex polygons (Hooge and Eichenlaub 1997) at these sites. Differences 

in distributions of king eiders during the wing molt and winter periods were examined using 

multiresponse permutation procedures (MRPP) in BLOSSOM (USGS, Fort Collins, Colorado, 

Cade and Richards 2001). We used the centroid of the minimum convex polygon (Hooge and 

Eichenlaub 1997) of the wing molt area and farthest south wintering area of each individual as 

the sampling unit and compared distributions by sex and among years. 

Movements 

We used two-way ANOVA to test for differences by sex and year in the timing of molt 

migration, residence at wing molt sites, fall migration, and spring migration. Significant 

differences among years were further examined using Tukey multiple comparison procedures. 

We calculated migration distance as the distance between as many subsequent locations that 

passed filtering requirements as possible per individual and corrected for curvature of the earth. 

Latitude of wing molt and wintering sites was calculated as the centroid of minimum convex 

polygons (Hooge and Eichenlaub 1997) created in ArcView GIS using Lambert Equal Area 

Azimuthal projection. 

Beaufort Sea Location Characteristics 

We used two-way ANOVA on ranked data to test for differences by sex and season in 

water depth and distance from shore of eider locations. Water depth at eider locations was 

calculated using a bathymetric shapefile with 10-m contour intervals compiled by the Alaska 

Science Center (1997). Distance from shore was calculated using ArcView GIS as the distance 

from an eider location to a 1:250,000 polyline shapefile (Soluri and Woodson 1990) of the 

Alaskan coastline. Because distance from shore and water depth were significantly correlated (rs

= 0.614, P < 0.001), we report results from water depth analysis only. 

Variation in the number of days an eider spent in the Alaskan Beaufort Sea was examined 

using multiple regression. Residence time of a king eider was calculated as the number of days 

from the first day an eider entered the sea until the date of the last location within the sea. 

Explanatory variables within the model included sex, season (post-breeding vs. spring), year, and 

standardized Julian date of an individual’s first location within Beaufort Sea. Julian date of an 

eider’s first location within the sea was standardized to allow season to be included in the 

analysis as a class variable. Standardized Julian date was calculated as the difference between 

11
the Julian day of an individual’s first location within the Beaufort Sea and the Julian day the first 

transmittered eider arrived in the sea each season. We included the first order interaction terms 

sex with season, year, and standardized Julian date. 

RESULTS 

Distribution and Use Areas 

Beaufort Sea. Distributions of king eider locations during spring did not differ among 

years (δ149 = -0.70, P = 0.16). Distributions of male locations during post-breeding did not differ 

among years (δ258 = -1.54, P = 0.079). Post-breeding distribution of female locations in 2003 

differed significantly from those in 2002 (δ58 = -6.41, P < 0.001) and 2004 (δ58 = -5.79, P = 

0.001); however, 2002 and 2004 distributions did not differ (δ60 = 0.81, P = 0.99). 

Distributions of king eider locations in the Alaskan Beaufort Sea differed by sex during 

the post-breeding period (δ516 = -26.38, P < 0.001), but not during spring migration (δ41 = -1.67, 

P = 0.068). Female locations tended to be concentrated in Harrison Bay and Smith Bay during 

post-breeding, while male locations were more widely dispersed in the Alaskan Beaufort Sea 

from Oliktok Point to Point Barrow (Figure 1). 

Spring and post-breeding distributions of eiders differed significantly (δ91 = -26.36, P < 

0.001). Spring locations were scattered from Point Barrow to the Canadian border with over 

40% of the locations found > 20 km offshore. Core use areas during the post-breeding period 

were located nearshore and distributed uniformly between the Kuparuk capture site and Point 

Barrow (Figure 2). 

The post-breeding distributions of male and female king eiders captured at Kuparuk 

differed significantly from distributions of those captured at Teshekpuk (male δ94 = -10.64, P < 

0.001, female δ86 = -17.70, P < 0.001). Females from Kuparuk were concentrated in Harrison 

Bay while core use areas of Teshekpuk females were located in Smith Bay. Locations of male 

eiders captured at Teshekpuk Lake were widely dispersed in the Beaufort Sea which resulted in a 

large core use area that covered the majority of the continental shelf from Point Barrow to 

Harrison Bay. Males captured at Kuparuk were more concentrated in small areas resulting in 

scattered dense core use areas off Oliktok Point and in Harrison and Smith Bays (Figure 3). 

Post-breeding and spring staging. Post-breeding staging areas for male and female king 

eiders included the Alaskan Beaufort Sea, Ledyard Bay, and the Chukotsk Peninsula (Figure 4). 

Spring staging areas for king eiders in this study were located outside the Alaskan 

Beaufort Sea in the Chukchi Sea and Canadian Beaufort Sea. All transmittered eiders returning 

to the arctic coastal plain of Alaska and Canada in spring staged in Ledyard Bay in the Chukchi 

Sea prior to entering the Beaufort Sea. Female king eiders exhibited fidelity to nesting areas by 

returning to sites near the capture site. Male king eiders migrated to Russia, Alaska, and Canada 

in the spring, presumably following females to their breeding grounds. Five of 15 males 

returning to breeding areas in the spring appeared to forego breeding and staged offshore in the 

Canadian Beaufort Sea (Figure 4). 

Wing molt and winter. During wing molt, king eiders were located in areas along the 

Chukotsk, Kamchatka, and Alaska Peninsulas, as well as St. Lawrence Island, Anadyr, Olyutor, 

Karagin, Bristol and Kuskokwim Bays, the Beaufort Sea, and the coast of Russia near Khatyrka 

(Table 2, Figure 5). In 2002, one female molted wing feathers in the Alaskan Beaufort Sea prior 

12
to moving to wintering areas in the Bering Sea. MRPP did not distinguish any differences in 

distribution of wing molt locations by sex (δ59 = 0.41, P = 0.57) or year (δ59 = 0.06, P = 0.44). 

Eiders wintered along the Chukotsk, Kamchatka, and Alaska Peninsulas, Olyutor and 

Bristol Bays, and the Gulf of Alaska (Table 2, Figure 6). MRPP did not distinguish any 

differences in distribution of winter locations by sex (δ29 = -0.82, P = 0.16) or year (δ29 = 0.47, P

= 0.59). 

Figure 1. Post-breeding distributions of king eiders (34 male, 26 female) 

within the Alaskan Beaufort Sea, 2002–2004. 

20 0 20 40 60 Kilometers

20 0 20 40 60 Kilometers

CANADA

Beaufort 

Sea

Study area

Ledyard 

Bay

Bering Sea

ALASKA

MALE

FEMALE

Post-breeding 

Male core use area

Female core use area

95 % contour

Kuparuk

capture site

Teshekpuk 

Lake

Smith Bay

Oliktok Pt.

Point Barrow

Colville River

Sagavanirktok River

Teshekpuk 

capture site

Harrison Bay

Point Barrow

Teshekpuk 

capture site

Teshekpuk 

Lake

Harrison Bay

Kuparuk

capture site

Oliktok Pt.

Smith Bay

Colville River

Sagavanirktok River

BEAUFORT SEA

BEAUFORT SEA

13
Figure 2. Post-breeding and spring distributions of satellite-tagged king 

eiders in the Alaskan Beaufort Sea, June 2002 – September 2004. 

Distributions include locations from 60 king eiders during post-breeding 

and 24 king eiders during spring.

40 0 40 80 Kilometers

Kuparuk 

capture site

Smith 

Bay

Point 

Barrow

Colville River

Sagavanirktok Rive

Teshekpuk r

capture site

Harrison Bay

CANADA

BEAUFORT SEA

SEASON

Spring core use area

Spring 95 % contour

Post-breeding core use area

Post-breeding 95 % contour

Figure 3. Post-breeding distributions within the Alaskan Beaufort Sea of 

king eiders captured at Kuparuk and Teshekpuk Lake on the North Slope 

of Alaska. Distributions include locations from 15 king eiders captured at 

Kuparuk and 12 king eiders captured at Teshekpuk Lake in 2004. 

20 0 20 40 60 Kilometers

CAPTURE SITE

Teshekpuk female 

Teshekpuk male 

Kuparuk female 

Kuparuk male 

Post-breeding core use areas

Kuparuk

capture site

Teshekpuk 

Lake

Smith Bay

Oliktok Pt.

Point Barrow

Colville River

Sagavanirktok River

Teshekpuk 

capture site

Harrison Bay

BEAUFORT SEA

14
Figure 4. Staging areas of satellite transmittered king eiders during spring and wing 

molt migration. 

15
Figure 5. Distribution of 59 satellite transmittered king eiders during 2002 – 2004 

wing molt periods. Areas occupied by two or more eider locations over the three 

years of the study are outlined by a dashed grey line.

 

16
Figure 6. Distribution of 29 satellite transmittered king eiders during 2002 – 2003 at 

farthest south wintering sites. Areas occupied by two or more eider locations over the 

two years of the study are outlined by a dashed grey line. 

17
Table 2. Proportion of male and female satellite transmittered king eiders captured on 

the North Slope of Alaska located in major wing molt and wintering areas in 2002 – 

2004. 

2002 2003 2004 

Location Male Female Male Female Male Female 

WING MOLT AREA (n) (11) (10) (9) (2) (14) (13) 

Russia 

 Karagin Bay 0.18 0.10 0 0 0 0 

 Khatyrka 0 0 0 0 0.14 0.15 

 Anadyr Bay 0.18 0.10 0.44 0 0.07 0.08 

 Chukotsk Peninsula 0.18 0.50 0.33 1.00 0.43 0.46 

Alaska 

 St. Lawrence Island 0.18 0.10 0 0 0.21 0.08 

 Bristol Bay 0 0.20 0.11 0 0.07 0.15 

WINTERING AREA (n) (10) (8) (9) (2) 

Russia 

 Kamchatka Peninsula 0.30 0 0.11 0 

 Olyutor Bay 0.10 0.38 0.22 0 

 Chukotsk Peninsula 0.10 0.12 0.22 0.50 

Alaska 

 Bristol Bay 0.30 0 0 0 

 Alaska Peninsula 0.10 0.38 0.33 0.50 

 Gulf of Alaska 0.10 0.12 0 0 

Movements 

 Mean dates of dispersal from breeding areas and arrival at wing molt sites differed by sex 

(dispersal from breeding: F1, 59 = 75.28, P < 0.001; arrival at molt site: F1, 59 = 65.79, P < 0.001) 

and among years (dispersal from breeding: F2, 59 = 7.18, P < 0.01; arrival at molt site: F2, 59 = 

3.98, P = 0.02). Female eiders dispersed from breeding areas and arrived at wing molt sites later 

than males in all years (Table 3, Figure 7). 

Average number of days at wing molt sites varied by year (F2, 55 = 4.99, P = 0.01) with 

eiders spending significantly more days at wing molt sites in 2003 (74 ± 4 days) than either 2002 

(57 ± 3 days) or 2004 (53 ± 2 days). Number of days at wing molt sites did not vary by sex (F1, 

18
55 = 2.41, P = 0.13). Females dispersed from wing molt sites later than males (F1, 55 = 5.57, P = 

0.02, Table 3). Dispersal date from wing molt sites did not vary by year (F2, 55 = 1.57, P = 0.22). 

Arrival date at breeding areas the following year did not vary by sex (F1, 18 = 1.64, P = 

0.22) or year (F2, 18 = 0.01, P = 0.92). 

The year/sex interaction term was not significant in all previous two-way ANOVAs (P > 

0.10). 

19
Table 3. Mean and range of dispersal dates from breeding areas, arrival at wing molt sites, 

dispersal from wing molt sites, and arrival at subsequent breeding areas for 60 king eiders 

captured on the North Slope of Alaska in 2002 – 2004. 

Dispersal 

from 

breeding 

(n) 

Range 

Arrival

at 

molt 

(n) 

Range 

Dispersal 

from 

molt 

(n) 

Range 

Arrival 

at 

breeding 

(n) 

Range 

SEX 

Male 23 Jun 

(33) 

14 Jun – 

4 Jul 

31 Jul 

(33) 

18 Jul – 2 

Sep 

2 Oct 

(33) 

13 Sep – 

12 Nov 

12 Jun 

(12) 

7 – 24 

Jun 

 

Female 

14 Jul 

(27) 

21 Jun – 

8 Aug 

28 Aug

(27) 

5 Aug – 

13 Sep 

17 Oct 

(23) 

16 Sep – 9 

Nov 

11 Jun 

(7) 

7 – 12 

Jun 

YEAR 

2002 29 Jun 

(21) 

14 Jun – 

26 Jul 

10 Aug

(21) 

21 Jul – 8 

Sep 

5 Oct 

(19) 

16 Sep – 9 

Nov 

11 Jun 

(12) 

7 – 24 

Jun 

2003 30 Jun 

(12) 

20 Jun – 

30 Jul 

8 Aug 

(12) 

18 Jul – 4 

Sep 

15 Oct 

(11) 

23 Sep – 

12 Nov 

12 Jun 

(7) 

6 – 23 

Jun 

2004 6 Jul 

(27) 

19 Jun – 

7 Aug 

16 Aug

(27) 

27 Jul – 

12 Sep 

8 Oct 

(26) 

12 Sep – 

29 Oct NA NA 

ALL 3 Jul 

(60) 

14 Jun – 

8 Aug 

13 Aug

(60) 

18 Jul – 

13 Sep 

9 Oct 

(56) 

13 Sep – 

12 Nov 

12 Jun 

(19) 

7 – 24 

Jun 

20
150 175 200 225 250 275 300 325

Wing molt migration

Wing molt

Female Male

2002

2003

2004

2002

2003

2004

Julian date

10

9

14

10

9

14

11

3

13

11

2

12

June August October

Figure 7. Mean number of days spent on wing molt migration and at wing molt sites 

for satellite transmittered king eiders for years 2002 – 2004. Sample sizes for the 

number of individual eiders used to calculate mean days of wing molt migration and 

duration at wing molt sites are represented respectively by the italicized number on the 

left and right sides of the bars, respectively. Ranges associated with dates of dispersal 

from breeding areas, arrival at wing molt sites, and dispersal from wing molt sites are 

found in Table 3. 

Beaufort Sea Location Characteristics 

Water depth at king eider locations differed by sex (F1,548 = 16.68, P < 0.001) and season 

(F1,548 = 20.12, P < 0.001) with a significant interaction between sex and season (F1,548 = 42.65, 

P < 0.001. During the post-breeding period, females were in shallower water (11.7 ± 0.8 m) than 

males (12.6 ± 0.4). ) During spring migration, female locations were in deeper water (28.8 ± 3.1 

m) than male locations (11.1 ± 1.8). 

Significant variation in residence time of transmittered king eiders within the Beaufort 

Sea was explained by sex (t1,69 = -2.98, P = 0.004), season (t1,69 = 3.66, P < 0.001), and 

standardized Julian date of first location within the sea (t1,69 = -4.89, P < 0.001, Figure 8). Year 

(t1,69 = -0.35, P = 0.728), sex*year (t1,69 = -0.06, P = 0.956), sex*season (t1,69 = -0.88, P = 0.383), 

and sex*Julian date (t1,69 = 1.90, P = 0.062) explained little variation in residence times. Females 

moved into the Beaufort Sea almost 2 weeks later than males in the spring and 20 days later than 

males during the post-breeding periods (Table 4, Figure 9). They spent almost twice as many 

21
days on average in the sea than males in spring and more than a week longer than males during 

post-breeding (Table 4, Figure 9). 

Table 4. Mean (± SE) residence time and date of first location within the Alaskan Beaufort Sea 

of transmittered king eiders during post-breeding (n = 60 eiders) and spring migration (n = 24 

eiders), June 2002 – September 2004. 

MALE FEMALE 

Residence time 

(days) Mean Range Mean Range 

Post-breeding 18.2 ± 1.6 1 – 48 26.9 ± 2.4 14 – 62 

Spring 7.3 ± 2.9 1 – 15 13 ± 3.7 4 – 20 

Date 

Post-breeding 25 Jun 16 Jun – 4 Jul 15 Jul 18 Jun – 8 Aug 

Spring 13 May 30 Apr – 20 May 26 May 17 May – 8 Jun 

22
0

10

20

30

40

50

60

70

0 10 20 30 40 50 60

Standardized Julian date

Residence time (days)

Spring female

Post-breeding female

Spring male

Post-breeding male

Figure 8. Plot of residence time and standardized date of arrival in 

the Alaskan Beaufort Sea of king eiders (n = 60) during spring and 

post-breeding periods. 

120 140 160 180 200 220 240 260

Julian date

male

male

female

female

POST-BREEDING SPRING

May July Sept

Figure 9. Mean range of residence time (days, dark bar) and range (grey bar) 

transmittered king eiders in the Alaskan Beaufort Sea during spring and post-breeding 

periods. 

23
DISCUSSION 

Distribution and Use Areas 

Beaufort Sea. Hundreds of thousands of king eiders pass through the Beaufort Sea each 

year during post-breeding and spring migrations (Suydam et al. 2000). Every king eider we 

transmittered on the North Slope of Alaska spent at least 1 day in the Alaskan Beaufort Sea after 

the breeding season. More than 80% of our transmittered eiders spent more than 2 weeks staging 

offshore prior to beginning molt migration, suggesting that the sea is an important migration 

flyway and staging area for this species. 

Concentrations of eiders at Harrison Bay and Smith Bay in July were consistent with the 

findings of Fischer et al. (2002) and Dickson et al. (2000). During post-breeding aerial surveys 

of the central Beaufort Sea, Fischer et al. (2002) recorded their highest densities of king eiders in 

deep water (>10 m) areas of Harrison Bay in July. Stehn and Platte (2000) analyzed these same 

aerial survey data and calculated a density of 3.6 king eiders per km2

 in the deep water (>8 m) 

area from the Kogru River to Oliktok Point. Dickson et al. (2000) described Harrison and Smith 

Bays as summer staging areas for king eiders transmittered on breeding grounds at Victoria 

Island, Northwest Territories and Prudhoe Bay, Alaska. 

In this study, Smith Bay was an area used more heavily by post-breeding female eiders 

than male eiders. Troy (2003) found the area around Smith Bay to be an important use area for 

North Slope-breeding female spectacled eiders (Somateria fischeri). After leaving the breeding 

grounds, 90% of his tagged females spent over 70% of their time in and around Smith Bay prior 

to departing the Beaufort Sea. He speculated that high ice cover in Smith Bay early in the postbreeding period prevented male spectacled eiders from using this area. Severe ice conditions 

early in the summer may also have reduced the amount of time transmittered male king eiders 

spent in Smith Bay. Shore-fast ice in the Beaufort Sea generally begins to move offshore in 

early July creating open water habitat nearshore (Craig et al. 1984). The broad distribution of 

male locations in the sea after breeding may reflect high (>75%) ice cover in June which forces 

male king eiders to dispersed pockets of open water during post-breeding. 

Post-breeding and spring distribution of king eider locations in the Alaskan Beaufort Sea 

overlapped very little. Short residence times and deep water at spring locations suggest that king 

eiders may be using the Alaskan Beaufort Sea as a migration corridor rather than a staging area 

during this period. 

Post-breeding and spring staging. As mentioned above, king eiders staged more than 

two weeks on average in the Beaufort Sea after breeding. Staging areas outside the Beaufort Sea 

included Ledyard Bay in the Chukchi Sea and the Chukotsk Peninsula. Dickson et al. (2000) 

described the northern part of Ledyard Bay near Icy Cape as a fall staging area for king eiders 

transmittered in Canada migrating to wing molt sites in the Bering Sea. 

During spring migration, our transmittered king eiders that returned to breed in Alaska 

and western Canada did not appear to stage within the Alaskan Beaufort Sea. Ledyard Bay may 

be a more critical stopover area during spring migration for foraging and resting. 

Wing molt and winter. Unlike spectacled and Steller’s eiders (Polysticta stelleri) 

(Petersen 1980, Petersen et al. 1999), male and female king eiders exhibited no sexual 

segregation of wing molt sites. The apparent lack of successfully breeding females in this study 

may explain our inability to detect any sexual segregation. During the course of the study, we 

found three of our transmittered hens incubating eggs, but timing of dispersal from breeding 

24
areas suggested none successfully fledged young. There is some evidence that female eiders that 

successfully raise young to fledging may molt flight feathers closer to the breeding grounds 

(Petersen et al. 1999), possibly in terrestrial environments (Knoche 2004). The distribution of 

wintering sites also did not differ between male and female king eiders. This lack of sexual 

segregation would be predicted for waterfowl species that, like king eider, form pair bonds on 

wintering grounds (Hepp and Hair 1984) or use marine habitat during winter (Diefenbach et al. 

1988). 

Wing molt sites for king eiders in this study were similar to those found by Dickson et al. 

(2000), with the addition of molting areas located in the Alaskan Beaufort Sea, Olyutor Bay, and 

on the west side of the Kamchatka Peninsula. We found additional wintering areas in Olyutor 

Bay, at the southern most tip of the Kamchatka Peninsula, and in Anadyr Bay. Both wing molt 

and wintering sites for our sample of king eiders were widely dispersed along the coastline of the 

Bering Sea supporting the results of Pearce et al. (2003) which revealed little spatial genetic 

structure within this population. 

Movements 

For Alaskan-breeding king eiders, differences between sexes in dispersal dates from 

breeding grounds, arrival dates at wing molt sites, and departure dates from wing molt sites were 

consistent with those captured in western Canada (Dickson et al. 2000), king eiders molting 

flight feathers in Greenland (Frimer 1994), and with other eider species (Petersen 1981, Petersen 

et al. 1999). The later chronology of molt migration in 2004 suggests inter-year variation in the 

timing of wing molt in king eiders. The interrelationship of reproductive and wing molt periods 

in waterfowl has been demonstrated previously, and annual variation in the timing of nesting 

tends to affect the molt chronology of females more than males (Leafloor and Ankney 1989, 

Hohman et al. 1992). Postbreeding female waterfowl may have less time for premigratory 

fattening, potentially leading to a cascading delay in timing of arrival at wing molt, wintering, 

and breeding sites the following year (Hohman et al. 1992). 

Beaufort Sea Location Characteristics 

The earlier timing of male king eiders in the Beaufort Sea relative to females is consistent 

with previous eider studies (Petersen et al. 1999, Dickson et al. 2000, Troy 2003). Male king 

eiders disperse from breeding grounds at the onset of incubation, while female timing is probably 

dependent on her success or failure as a breeder. Males spent fewer days staging in the Beaufort 

Sea post-breeding than females. Female king eiders may need to remain in the Beaufort Sea 

longer than males prior to molt migration to replenish fat stores depleted during egg-laying and 

incubation. Female eiders rely on endogenous reserves for egg-laying and forage very little 

while incubating (Korschgen 1977, Kellet 1999). King eiders nesting at Karrak Lake, Northwest 

Territories lost 32% of their pre-incubation body mass during incubation (Kellet 1999). 

We found no apparent trend of residence time with date of arrival for male king eiders 

and the opposite trend for females. Timing of female staging and migration in the Beaufort Sea 

may be constrained by subsequent life history events. Female ducks with longer reproductive 

efforts may have limited time to replenish diminished fat stores before beginning molt migration, 

especially in the high arctic where advancing winter weather could reduce forage quality or 

entrap flightless birds in advancing ice at wing molt sites (Salomonsen 1968, Hohman et al. 

25
1992). In spring, early arrival on breeding grounds may provide reproductive advantages to 

nesting female waterfowl (Johnson et al. 1992). Timing of male molt migration appears to be 

highly synchronized in most waterfowl (Hohman et al. 1992), and this is supported by the 

behavior of our transmittered male eiders after breeding. 

ACKNOWLEDGEMENTS 

Financial support for this research was provided by Coastal Marine Institute (University 

of Alaska, Fairbanks) and Minerals Management Service. Additional support was provided by 

ConocoPhillips, Alaska, Inc., the North Slope Borough, U.S.G.S. Alaska Cooperative Fish and 

Wildlife Research Unit, Sea Duck Joint Venture, UA Foundation- Angus Gavin grant, Institute 

of Arctic Biology, and U.S. Fish and Wildlife Service. We would like to acknowledge the 

valuable input and technical assistance provided by C. Monnett, J. Gleason, B. Anderson, P. 

Martin, T. Obritschkewitsch, C. Rea, A. Lazenby, L. McDaniel, J. Harth, D. Douglas, R. 

Suydam, D. Troy, P. Howey, B. Griffith, F. Huettmann, and C. MacIntyre. For assistance 

trapping eiders, we would like to thank E. Duran, L. Guildehaus, A. Prevel, K. Roby, R. Acker, 

S. Backensto, C. Adler, R. McGuire, and M. Knoche. L. Dickson, J. Gleason and an anonymous 

reviewer provided helpful comments on this paper. We are also grateful to our veterinarian C. 

Scott and veterinary technicians K. Adams and M. Carlson for performing the surgeries. Use of 

brand names within this report does not imply endorsement by U.S.G.S. 

26
STUDY PRODUCTS 

Presentations:

Phillips, L., A. Powell, E. Taylor. 2005. Use of the Beaufort Sea by king eiders. 10th Annual 

MMS Information Transfer Meeting, Anchorage, AK. 

Powell, A. N., E. Rexstad, E. Taylor, and L. Phillips. 2005. Importance of the Beaufort Sea to 

king eiders (Somateria spectabilis). CMI Annual Review, University of Alaska, Fairbanks, 

AK (L Phillips, presenter). 

Phillips, L. and A. N. Powell. 2005. Large-scale movements and habitat use of king eiders 

throughout the nonbreeding season. Annual Meeting, Pacific Seabird Group/Waterbird 

Society Meeting, 19–23 January, Portland, OR. 

Phillips, L., A. N. Powell, and E. Taylor. 2004. Molt migration and ecology of king eiders. 

Annual Meeting, American Ornithologists Union, 16–21 August, Quebec City, QC, 

Canada. 

Phillips. L. A., A. N. Powell, and E. Taylor. 2004. Migration ecology of king eiders. Alaska 

Forum on the Environment, Anchorage, AK. 

Phillips, L., A. N. Powell, and E. Taylor. 2004. Migration ecology of king eiders. CMI Annual 

Review, University of Alaska, Fairbanks, AK. 

Phillips, L., R. McGuire, and M. Knoche. 2004. Alaska's eiders. Presentation at Alaska Bird 

Observatory’ seminar series. 

Phillips, L., A. N. Powell, and E. Taylor. 2003. Importance of the Beaufort Sea to King Eiders. 

CMI Annual Review, University of Alaska, Fairbanks, AK. 

Phillips, L. M., A. N. Powell, and E. J Taylor. 2002. Importance of the Alaskan Beaufort Sea to 

king eiders during fall migration. Poster; North American Sea Duck Conference, 6–10 

November 2002, Victoria, B.C. 

Powell, A. N. 2002. Ecology of King Eiders on Alaska's North Slope. MMS Information 

Transfer Seminar, Anchorage, AK. 

 

Reports:

Phillips, L. M. 2005. Migration ecology and distribution of king eiders. M.S. Thesis, 

University of Alaska, Fairbanks, AK. 

Powell, A. N., L. M. Phillips. E. A. Rexstad, and E. J. Taylor. 2004. Importance of the Alaskan 

Beaufort Sea to king eiders (Somateria spectabilis). Annual Report, CMI, University of 

Alaska, Fairbanks, AK. 

Powell, A. N., E. Taylor, E. Rexstad, and L. Phillips. 2004. Importance of the Alaskan Beaufort 

Sea to King Eiders. Report to the Sea Duck Joint Venture. 

http://www.seaduckjv.org/ssna.html 

Powell, A. N., L. M. Phillips. E. A. Rexstad, and E. J. Taylor. 2003. Importance of the Alaskan 

Beaufort Sea to king eiders (Somateria spectabilis). Annual Report, CMI, University of 

Alaska, Fairbanks, AK. 

Powell, A. N., E. Taylor, E. Rexstad, and L. Phillips. 2003. Importance of the Alaskan Beaufort 

Sea to king eiders. Report to the Sea Duck Joint Venture. 

http://www.seaduckjv.org/ssna.html 

Powell, A. N., L. M. Phillips. E. A. Rexstad, and E. J. Taylor. 2002. Importance of the Alaskan 

Beaufort Sea to king eiders (Somateria spectabilis). Annual Report, CMI, University of 

Alaska, Fairbanks, AK. 

27
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