Somateria spectabilis

Geographic Range

King eiders ( Somateria spectabilis ) are found in Holarctic coastal regions. They are predominantly found in North America and eastern Russia but also Scandinavia. This is a migratory species that breeds in the northern latitudes of its distribution, nesting along the coast of the Arctic Ocean from northeastern Russia and Alaska to the islands of the Northwest and Nunavut Territories of Canada, as well as the west shore of Hudson Bay and portions of Greenland.

The North American population is separated into two subpopulations distinguished by wintering area: the Atlantic (eastern) and Pacific (western). The Pacific population winters in the bays of the Bering Sea (Olyutor and Bristol Bays and the Gulf of Alaska) and along the Chukotsk, Kamchatka, and Alaska Peninsulas of Alaska and eastern Russia. The Atlantic population winters on the coasts of the eastern Canadian provinces, particularly in the Gulf of St. Lawrence, and the New England area of the United States with a sparse wintering population in Greenland. There have been rare, reported cases of king eiders venturing as far south as California and Florida and even more peculiar occurrences in inland regions, including central Canada, the United States, and continental Europe. The non-breeding range of king eiders is primarily characterized by shallow seas and low percentage of ice cover, thus greater foraging opportunity.

• Biogeographic Regions
• nearctic nearctic
  • native native
• palearctic palearctic
  • native native
• arctic ocean arctic ocean
  • native native
• pacific ocean pacific ocean
  • native native

• Other Geographic Terms
• holarctic holarctic

Habitat

King eiders are restricted to waters free of ice, compared to related species, common ( Somateria mollissima ) and spectacled ( Somateria fischeri ) eiders, which may tolerate ice obstruction of 75% or greater. If restricted by ice, king eiders may move to an area with greater forage ability. Wintering areas of king eiders are generally shallow (~37.9 m ± 3.2 m), as near shore as possible (though further from shore than S. mollissima and S. fischeri ), with low salinity and ice cover. King eiders generally occur 11.1 km ± 0.8 km from shore due to ice formation. In Norway, king eiders demonstrated a preference for cobble substrate at depths up to 40.0 m, avoiding urchin barrens and sand or rock substrate.

Nest sites of king eiders are selected based on seclusion and cover. Generally, female king eiders nest on islands, near water, with willow cover ( Salix species). Island nesting seems to be preferential to mainlandnesting and small and medium sized islands are favored (less than 0.0002 km2 and 0.002 to 0.081 km2, respectively). Nests are typically dispersed 5.8 to 62.0 m from the water. Suitable nesting sites on the tundra mainland may also be used, though island nesting king eiders demonstrate higher nest success than mainland nesters (30 to 89% and 0 to 22%, respectively). Nest site selection was hypothesized to be associated with more aggressive, nest-protecting bird species, such as terns ( Sterna species) but this is no longer thought to be true. Brood rearing takes place on land, with daily movement of hens with broods 507 meters per day ± 68.7 days prior to fledging, which occurs in salt water.

During the vulnerable molting period, king eiders exhibit unique habitat preferences for foraging sites. Alaskan molting king eiders were found foraging in coastal areas characterized by benthic regions of silt, at depths of 15 to 25 m (19.3m ± 2.5), and 6.1 km ± 0.4 from shore and moved further offshore to rest at night). Ice formation is a critical limiting factor while king eiders are unable to fly to more open foraging areas.

• Habitat Regions
• temperate temperate
• polar polar
• terrestrial terrestrial
• saltwater or marine saltwater or marine

• Terrestrial Biomes
• tundra tundra

• Aquatic Biomes
• lakes and ponds
• coastal coastal

• Other Habitat Features
• estuarine estuarine

Physical Description

King eiders are sea ducks known for their ornate plumage and are sexually dimorphic. The breeding plumage of males (late autumn through mid-summer) includes a distinguishing reddish-orange bill and an enlarged yellow frontal lobe rimmed with black. The crown, nape and eyebrows are light grayish blue, the cheeks and iridescent pale green, the mantle, breast and scapulars are white (the breast sometimes has a yellowish buff), and most of the body is black. The sides of the rump and portions of the lesser and median covert feathers are white. Very distinct are the two vertical, triangular “sails” on the back formed by long extensions of the black scapular feathers. The feet are yellow with blackish nails.

The breeding plumage of female king eiders (late summer through spring) is mostly reddish-brown. The feathers of the sides and flanks are dark brown/black in the center and outlined in tawny brown, a scalloped pattern on the breast and belly, the primaries and secondaries are blackish but the secondaries are tipped in white/light brown, and the underwing coverts and axillaries are a dull white. The bill is olive or yellowish gray with a less pronounced frontal lobe than the males. The coloration female king eiders is variable. The feet are of a dusky complexion.

The eclipse phase of male king eiders (mid-summer through early autumn) is mostly brown, similar to the female except for the white patch on the forewing and rump. The bill is pale orange and the frontal lobe is reduced in size with dark spots. The eclipse phase of the female (early summer through late summer) is similar to the breeding plumage but the head and neck are larger and more distinct.

Male king eiders in their alternative plumage can be distinguished from other male eiders by the large orange lobe and square-shaped head and less white on the upper and undersides of the wings that male common ( Somateria mollissima ) and Spectacled eiders ( S. fischeri ). King eiders are smaller than common eiders but larger than Steller’s eider. Female king eiders have a more rounded head shape, a shorter bill, and more compact body compared to female common eiders. At close ranges, king eiders have a distinctive upturned (“smiling”) gape line.

King eider hatchlings are a downy, dark grayish brown with various cryptic patterns. Juvenile plumage, which is fully developed at one month of age and similar in both sexes, is pale buffy brown with black-olive streaks along the sides, the chin and throat are gray, and the back and rump are blackish. The breast feathers are barred and the triangular “sails” are not yet developed.

King eiders are large: 1,200 to 2,100 g, and males are larger than females, though differences in body mass varies by location. Adult males and females in Alaska weigh on average 1668 and 1567 g, respectively; adult males in Greenland weigh an average of 1763 g; juvenile male and female king eiders in Alaska weigh 1573 and 1445 g, respectively. Average body measurements of adult males and females are: bill length-30.7 mm and 33.7 mm; wing length-280 mm and 275; tail length-83 mm and 81 mm; tarsus length-47.7 mm and 47.0 mm. These measurements may vary by plumage phase. The length of a king eider is from 46 to 64 cm and wingspan is from 89 to 102 cm.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger
• sexes colored or patterned differently
• male more colorful

Reproduction

Breeding kings eiders form seasonal pair bonds during the pre-breeding period, usually during or prior to the spring migration to breeding grounds. Males display their ornate plumage through numerous behaviors: pushing (see Communication and Perception), reaching (see Communication and Perception), wing flapping, and they often call softly. Females preen, wing-flap, and repeatedly dip their bills into the water. When ready to copulate, males will swim around a female performing various courtship displays and the female assumes the prone posture (lying flat on the water surface). Both sexes preen after copulation. Males have been observed mating with multiple females. Male king eiders usually accompany the female until part of the way through the nesting period.

• Mating System
• monogamous monogamous
• polygynous polygynous

King eiders breed once annually, arriving on the breeding ground in mid-June having already formed pair bonds. Demonstrating site fidelity, female king eiders return to within an average of 4 km from the nest site of the previous year and begin constructing a nest soon after snowmelt, usually in early June. Males do not demonstrate any parental tendencies and the female king eiders raise their precocial offspring independently. In preparation, females spend more than seven hours per day feeding: triple that of males, consuming 1.0 to 2.5 g of invertebrate biomass per minute to combat the energy requirements of egg development.

King eiders select nest sites that are either secluded or concealed to prevent predation as female king eiders use cryptic coloration to avoid predation and attempt to make themselves inconspicuous. Sites may be in varying vegetation on mainland tundra habitat (typically concealed) or on islands (typically secluded) and nest densities can vary widely (0 to 2 nests/km2 on mainland habitat and 46 to 198 nests/km2). It is thought that island nest sites are more secluded to reduce nest predation by arctic fox ( Alopex lagopus ), gulls ( Larus species), and jaegers ( Stercorarius ), which accounts for the second greatest cause of nest failure, following nest abandonment. Using the Mayfield nest success model, king eider nest success varies considerably, from 30 to 89%.

Nesting location in relation to the nearest water source varies for king eiders, ranging from ~5 to 594 m, which may be indicative of mammalian predators present in the area. If predominant, nests are generally closer to water. More isolated islands (smaller islands and larger islands far from the mainland) generally have the highest nest success, but there is conflicting evidence whether or not king eiders actively select such nesting locations. It has been hypothesized that eiders may nest near other species that aggressively protect their nests (such as gulls, Larus species).

King eider nests, typically 25 cm in diameter, are constructed by females by leaning forward on her breast and kicking debris with her feet, thus digging a shallow depression. Vegetation is added to the nest under and around the eggs as the eggs are laid and downy feathers are added progressively as the clutch nears completion. King eider eggs are about 60.0 to 70.0 g, elliptically-shaped, and pale-olive in color. Clutch size of king eiders ranges from 1 to 16 eggs (Palmer 1976) with an averages of about five eggs which are usually laid during mid-June to early-July. Clutch size typically decreases with later laying date. Early in the incubation period, males leave the females to raise their offspring.

During the 22 to 24 day incubation period, female king eiders rely primarily on endogenous fat stores, having been shown to lose 30% of pre-incubation body mass during incubation, but feed briefly on a daily basis to slow the depletion of fat reserves. If in poor condition, king eiders may not even attempt to nest and as body reserves are used, incubation constancy is reduced to feed. Hatch date of king eiders is mid to late July. Brood parasitism is not common in king eiders.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

Nesting female size (i.e. mass) is positively correlated with duckling size and condition, as broods of larger females have a greater survival rate, however, female size does not correspond with time of nesting and if nesting is delayed hatchling survival declines regardless. Additionally, earlier hatch dates and larger hatchling size typically lead to greater duckling survival. Larger king eider ducklings have been shown to exhibit a significant advantage in maximum swimming speed and growth rate than smaller ducklings, which may be advantageous when foraging for aquatic insects and escaping from predators.

Soon after hatching, female king eiders may move their brood away from the main nesting areas, on average 2.0 km over land, to more favorable habitats, such as inland tundra ponds, and during this period brood amalgamations may form. King eider hatchlings have been observed in large groups with several tending females, though the significance of these consolidations is unknown. These brood amalgamations range in size from 2 to 10 females and 7 to 29 ducklings. Ducklings may also be fostered in broods other than their own, although, it appears unlikely and probably accidental. The ducklings are precocial and feed without assistance and attending females may leave for short periods. Ducklings are largely independent by this time and do not depend on parental guidance.

Daily survival rates of king eider ducklings is 86%, and the overall survival rate up to 24 days old is estimated as 10% and whole broods experience and estimated 31% survival rate, which is similar to common eiders ( S. mollissima ). Complete brood loss (prior to hatching) is the most common source of duckling mortality (as with most waterfowl), but hatchlings are particularly susceptible to predation and mortality is greatest within the first days of life. The primary duckling defense is to dive or maternal defense against predators, of which glaucous gulls ( Larus hyperboreus ) and herring gulls ( Larus argentatus ) are most common. By the time hatchling king eider are 24 days old, they are considered fledglings, as closely resemble adults and accompany adult to marine feeding grounds.

• Parental Investment
• precocial precocial
• female parental care female parental care
• pre-fertilization
  • protecting
    • male
• pre-hatching/birth
  • protecting
    • female
• pre-weaning/fledging
  • protecting
    • female

Lifespan/Longevity

First-year survival of king eiders is 67%. Average adult survival is 94% and does not differ by sex or season. Considering the survival of hatchlings (10% survival to 24 days of age), the limiting factor of king eider populations is mortality of young individuals. Predation is the major limiting factor for egg and duckling survival, and death by exposure and starvation in adults may account for large die-offs besides predation. The longest living king eider known was nearly 19 years old, however, the oldest common eider ( S. mollissima ) was over 21 years old, indicating that king eiders may be able to live longer.

Behavior

King eiders are primarily seafaring ducks found swimming and diving using their large webbed feet, though they are capable of walking and running on land and ice. Like most ducks, king eiders perform rapid flight and typically fly in flocks less than 100 m above the ground, water, or ice. This species is highly gregarious—flocks may reach 10,000 individuals or more during migrations but during the rest of the year, smaller flocks (less than 100 individuals) are numerous. During migration, other species, such as common ( Somateria mollissima ), spectacled ( Somateria fischeri ), and Steller’s ( Polysticta stelleri ) eiders; long-tailed ducks ( Clangula hyemalis ); and common ( Uria aalge ) and thick-billed ( Uria lomvia ) murres, may migrate with king eiders. Migration of king eiders may be dictated by weather as eiders begin to migrate if wind direction if favorable.

Spring migration begins when favorable weather conditions arrive, generally taking place in May. King eiders molt their primary feathers soon after they arrive on the breeding grounds, but prior to laying eggs. During August through October adult birds molt their body feathers. The primaries are re-molted in September and October in preparation for the fall migration which takes place during November and December.

King eiders are diurnal species, which means, during the summer months of the high arctic they are active for nearly 24 hours each day. Daily activities of king eiders varies temporally, seasonally, and by sex. During the pre-breeding period, the activity budget of males and females are different due to energetic demands of egg production on the female. The percentage of time spent on each activity for males and females respectively are as follows: loafing: 67% and 51%; foraging: 10% and 30%; locomotion: 18% and 14%; reproduction (courtship, aggression): 6% and 5%. During the rest of the year, these percentages may change due to growth requirements (i.e. feather growth—molt).

King eiders are well known divers and forage on the sea floor at depths between 15 and 25 m but have been observed at depths up to 55 m. While rearing broods on tundra ponds, king eider ducklings and females commonly forage for invertebrates at depths of less than 1 m.

King eiders are highly social except during the breeding season when agonistic behavior is common when paired. Males are usually more aggressive than females and may, for example, display chin-lifting (rapidly lifting and exposing chin briefly), chasing, upward stretching (lifting head vertically and rearing out of the water exposing dorsal surface), and reaching (stretching head out over the water while arching back). These displays may also be directed at avian predators.

Similar displays are used by males as courtship displays. Pushing is the most common display, but upward stretching and wing-flapping are presented as well and accompanied by soft calls described as a wavering hoooooo or gug gug guggugug grooooooooo . These actions may be to court a female or protect her from advancing males. When ready to copulate, males will circle a female, repeating the displays. Females may also display by preening and wing-flapping, and when ready to copulate, a female will then assume a prone position (lying flat on the water).

While nesting, king eiders may nest in a solitary location or with others and nest density varies considerably: 2 nests/km2 to 198 nests/km2. During the nesting period king eiders are not thought to be territorial. King eiders may nest in association with other birds, especially those that actively protect their nest/offspring from predators, such as geese ( Chen species), gulls ( Larus species), and Arctic terns ( Sterna paradisaea ), however, there is little concluding evidence of this.

• Key Behaviors
• terricolous
• flies
• diurnal diurnal
• motile motile
• migratory migratory
• social social

Home Range

King eiders are a gregarious species and do not maintain a territory. The winter range of western North American population of king eiders are approximately 6905 km2 and individuals are known to travel between wintering sites leading to the extreme size of range.

Communication and Perception

Vocalizations between king eiders vary between males and females: males perform a wavering hooooo and may kwack if threatened. Females are known for various croaks, grunts, and kwacks . Wings of king eiders whistle in flight and observers may hear “clapping” as a flock of eiders pass due to contact of flapping wings of adjacent birds. Agonistic behavior of king eiders is primarily seen during the breeding season and activities such as chin-lifting (rapidly lifting and lowering the chin), chasing, and reaching (stretching the head and neck out low to the water) are common among males while females typically exhibit chin-lifting.

During breeding, male king eiders present their plumage and display several physical behaviors, such as pushing (repeatedly bowing their head-as if to push something-then lifting it while hooooo -ing), wing flapping, and reaching. Females have also been observed performing some of the same ritualistic behaviors as the males, although the validity of such actions as mating displays is unclear. When ready to mate, females of genus Somateria assume a prone posture-stretching the neck and head out as if to lie on the water.

Little is known about interspecies communication of eiders nor their perception. Investigations of related species, common eiders ( S. mollissima ), have shown that females defecate when flushed from their nest and mammalian predators may be dissuaded from predating the eggs by chemical repellants in the feces, which is surmised be true of king eiders as well. One might infer that king eiders have excellent eyesight, as do most aquatic, diving birds.

• Communication Channels
• visual visual
• acoustic acoustic
• chemical chemical

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Large sea ducks are hypothesized to feed on benthic prey that are sessile—allowing them to maximize intake. However, such prey often have protective mechanisms (i.e. hard shell) which ducks such as the king eider crush and grind in their gizzard, slowing the digestion rate. According to king eider gut content analyses, mollusks (bivalves, gastropods, polyplacophora, etc.) make up the majority of their diet and is their dominant food source, followed by crustaceans (malacostraca, cirripeds, etc.), echinoderms (asteroids, ophinuroids, echinoids, holothuroids), annelids, fish, and many other singular prey items. Female king eiders, while nesting, are omnivorous and feed on vegetation (such as willows, Carex species) and insects (midges [ Chironomidae ], bees and wasps [ Hymenoptera ], blowflies [ Calliphoridae ], fairy shrimps [ Anostraca ], and tadpole shrimps [ Notostraca ]) to prevent excessive loss of body reserves.

As stated previously, king eiders forage in substrate at depths of 15 to 25 m, but may dive deeper, foraging for greater than 90 seconds at a time and consume their prey prior to surfacing. They seem to prefer cobble or hard bottoms, avoiding urchin barrens, sand, and rock. As diurnal carnivores, king eiders rely on their eyesight to locate prey and they are able to take advantage of long daylight hours of the Arctic to forage. As with most diving ducks, a large supraorbital process is found to protect the eyes and salt glands of king eiders while foraging.

• Primary Diet
• carnivore carnivore
  • molluscivore molluscivore

• Animal Foods
• fish
• insects
• terrestrial non-insect arthropods
• mollusks
• aquatic or marine worms
• aquatic crustaceans
• echinoderms
• cnidarians
• other marine invertebrates

• Plant Foods
• leaves
• algae

Predation

Predation of nests by avian and mammalian predators may account for 66% of nest failures of king eiders. Island nest sites largely eliminate mammalian predators (Arctic foxes, Vulpes lagopus ) and are generally secluded enough to avoid avian predators, demonstrated by higher nest success. If disturbed by mammalian predators, common eiders ( S. mollissima ) defecate when flushed from their nest to dissuaded predation by chemical repellants, which is surmised be true of king eiders as well.

King eider ducklings are most heavily preyed on by glaucous gulls ( Larus hyperboreus ) and herring gulls ( Larus argentatus ), which usually takes places in the first two weeks of life due to undeveloped motor skills. Jaegers ( Stercorarius species) are also common predators of ducklings. Female duckling survival, in particular, seems to be lower than that of males, possibly due to size difference, as larger ducklings seem more able to swim, run, and dive faster and longer.

Adult king eiders are most susceptible to predation during molting periods. In response, while unable to fly, this species is often found in deeper waters away from coastal areas to rest at night. Predation of adult king eiders is occasionally attributed to snowy owls ( Bubo scandiacus ) and peregrine falcons ( Falco peregrinus ), although the incidence of each is low.

There are conflicting claims of whether hunting mortality of king eiders is effecting the populations size. Though fall hunting harvest is 3.7% to 6.9% of the total migrating population, which is not considered an over-harvest, other sources attribute declining populations of king and common eiders since 1976 to over-harvest. The bottom line is eider populations may be declining to stable. Additionally, subsistence harvest of an estimated 11,135 king eiders during spring, summer, and fall, a long standing tradition by indigenous peoples, is another significant source of mortality. Outside of mortality due to predation, inadequate food resources leading to starvation and exposure of king eiders is a significant source of mortality, especially during spring migration and during the molting period while the birds are flightless.

Ecosystem Roles

There is little information on intra-species and inter-species relationships of king eiders. There is some evidence to suggest king eiders nest in association with more aggressive birds (though this evidence is inconsistent and often conflicting), and there is no evidence that any species are commensal with king eiders nor brood parasites. Several species of flatworms have been documented parasitizing king eiders: Lateriporus teres , Fimbriarioides intermedia , Hymenolepis fallax , H. microstoma , and H. arctica and a parasitic worm-like animal Plymorphus botulus .

King eiders, eggs, ducklings, and adults, are actively depredated by avian and mammalian predators such as arctic fox ( Vulpes lagopus ), glaucous gulls ( Larus hyperboreus ), herring gulls ( L. argentataus ), jaegers ( Stercorarius species), snowy owls ( Bubo scandiacus ) and peregrine falcons ( Falco peregrinus ). Predation and reproductive success of king eiders seems to be tied to lemming populations: with high lemming numbers, king eider nest success increases and predation decreases. It is hypothesized that lemmings are preferred prey by mammalian predators of king eiders, which leads to increased nest success.

Economic Importance for Humans: Positive

As a Holarctic species, king eiders interact little with humans, thus providing few benefits besides subsistence hunting. King eiders, along with many other migratory bird species, provide an important source of protein for indigenous peoples in North America near the Arctic Circle. Additionally, the striking plumage of the adult male king eider is likely an attraction for tourists.

• Positive Impacts
• food food

Economic Importance for Humans: Negative

There are no known adverse affects of king eiders on humans.

Conservation Status

An assessment of king eiders populations by the Alaska Species Ranking System determined king eiders to be biologically vulnerable and action is needed. Analysis of migrating king eiders past Barrow Point suggest that migratory populations in the Beaufort Sea declined by 56% from 1976 to 1996. However, other indices have shown an increased population. Thus, king eiders populations are believed to be moderately declining or remaining constant at the current estimated breeding population of 340,000 to 380,000 birds. Viable nesting habitat under development by oil and gas companies may also be detrimental to king eiders. King eider natural history (i.e. age of sexual maturity, clutch size, diet, etc.) suggests the specie’s conservation status is of least concern, but many remaining research needs may mean king eiders could be threatened.

Additionally, king eiders appear to be heavily disturbed by boat traffic, causing stress to molting birds, and there seems to be corresponding shift in suitable molting areas since the 1950’s as a result of increase traffic. This is especially true in their wintering ranges, but little human impact has been recorded in nesting areas of king eiders. King eiders are also very susceptible to oil spills. Concentrations of lead, mercury, and barium levels are high in eider species, which is thought to be due largely to contamination of the breeding grounds where the chemicals are consumed by king eiders. Although the levels of these elements are not toxic, elevated levels of these trace elements in ducklings is alarming. According to the U.S. Fish & Wildlife endangered species list, related eider species, the spectacled and Steller’s eider ( S. fischeri and Polysticta stelleri , respectively) are threatened, though king eiders are not.

There was a unique event on Baffin Island during which approximately 110 king eiders crash landed into the ground. Researchers proposed that cataracts formed in the eyes of some of the birds due in part to a degenerative condition coupled with low temperatures and restricted visibility; however, this event is rare. There have been cases of king eider mortality by crashing into man-made structures which may become more prevalent as more of their range is developed.

Other Comments

Much of what is known about king eiders is from studies of the North American populations. Knowledge of European and Russian populations is lacking as well genetic drift during the breeding season. Additional understanding of the toll of subsistence harvest is necessary in the face of climate change, in order to ensure the continuation of the species, as well as the potential effects of oil and gas developments in the king eiders range. Hybridization of king and common eiders have been documented (male king eiders may display to female common eiders), which may threaten the genetic integrity of the two species though hybrid offspring appear infertile.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Caleb Eckloff (author), Northern Michigan University, Alec Lindsay (editor), Northern Michigan University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

References

American Ornithologists' Union, 1998. Check-list of North American Birds . Washington D.C.: American Ornithologists' Union.

Anderson, V., R. Alisauskas. 2001. Egg size, body size, locomotion, and feeding performance in captive King Eider ducklings. The Condor , 103(1): 195-199.

Bentzen, R., A. Powell, R. Suydam. 2009. Strategies for Nest-site selection by King Eiders. The Journal of Wildlife Management , 73(6): 932-938.

Bustnes, J., O. Lonne. 1997. Habitat partitioning among sympatric wintering Common Eiders Somateria mollissima and King Eiders Somateria Spectabilis. Ibis , 139(3): 549-554.

Byers, T., D. Dickson. 2001. Spring migration and subsistence hunting of King and Common Eiders at Holman, Northwest Territories, 1996-97. Arctic , 54(2): 122-134.

Clapp, R., M. Klimkiewicz, J. Kennard. 1982. Longevity records of North American Birds: Gaviidae through Alcidae. Journal of Field Ornithology , 53(2): 81-124.

Cramp, S., K. Simmons. 1977. The birds of the western Paleoarctic. Volume 1 . Oxford, U.K.: Oxford University Press.

Drury, W. 1961. Observations on some breeding water bird on Bylot Island. Canadian Field-Naturalist , 75: 84-101.

Falk, K., F. Merkel, K. Kampp, S. Jamieson. 2006. Embedded lead shot and infliction rates in common eiders Somateria mollissima and king eiders S. spectabillis wintering in southwest Greenland. Wildlife Biology , 12(3): 257-265.

Frimer, O. 1995b. Adaptations by the king eider (Somateria spectibilis) to its moulting habitat: Review of study at Disko, West Greenland.. Dansk Ornithologisk Forenings Tidsskrift , 89: 135-142.

Frimer, O. 1995. Comparative behavior of sympatric moulting populations of common eider (Somateria mollissima) and king eider (Somateria spectabilis) in central West Greenland. Wildfowl , 46: 129-139.

Frimer, O. 1997. Diet of moulting King Eiders Somateria spectabilis at Disko Island, west Greenland. Ornis Pennica , 74: 187-194.

Johnsgard, P. 1964. Comparative behavior and relationships of the Eiders. The Condor , 66(2): 113-129.

Kellett, D., R. Alisauskas. 1997. Breeding biology of King Eiders nesting on Karrak Lake, Northwest Territories. Arctic , 50(1): 47-54.

Kellett, D., R. Alisauskas, K. Mehl. 2003. Nest-site selection, interspecific associations, and nest success of King Eiders. The Condor , 105(2): 373-378.

Klimkiewicz, M., A. Futcher. 1989. Longevity records of North American birds supplement 1. Journal of Field Ornithology , 60(4): 469-494.

Lamothe, P. 1973. Biology of the king eider (Somateria spectabilis) in a freshwater breeding area on Bathurst, Island, N.W.T. Thesis . Edmonton, Alberta, Canada: University of Alberta.

Mallory, M., H. Gilchrist, S. Jamieson, G. Robertson, D. Campbell. 2001. Unusual migration mortality of King Eiders in Central Baffin Island. Waterbirds: The International Journal of Waterbird Biology , 24(3): 453-456.

Mauser, D., R. Jarvis, D. Gilmer. 1994. Survival of radio-marked mallard ducklings in northeastern California. The Journal of Wildlife Management , 58(1): 82-87.

McDougall, P., H. Milne. 1978. The anti-predator function of defecation of their own eggs by female Eiders. Wildfowl , 29: 55-59.

Mehl, K., R. Alisauskas, A. Buerger. 2007. King Eider (Somateria spectabilis) Brood Ecology: Correlates of Duckling Survival (Écologie d'élevage des couvées de Somateria spectabilis: Corrélations avec la survie des canetons). The Auk , 124(2): 606-618.

Merkel, F., A. Mosbech, S. Jamieson, K. Falk. 2007. The diet of king eiders wintering in Nuuk, Southwest Greenland, with reference to sympatric wintering common eiders. Polar Biology , 30(12): 1593-1597.

Miller, E., J. Williams, S. Jamieson, H. Gilchrist, M. Mallory. 2007. Allometry, bilateral asymmetry and sexual differences in the vocal tract of common eiders Somateria mollissima and king eiders S. spectabilis. Journal of Avian Biology , 38(2): 224-233.

Mosbech, A., D. Boertmann. 1999. Abundance and Reaction to Aerial Surveys of Post-breeding King Eiders (Somateria spectabilis) in Western Greenland. Arctic , 52(2): 188-203.

Oppel, S., A. Powell, M. Butler. 2011. King Eider foraging effort during the pre-breeding period in Alaska. The Condor , 113(1): 52-60.

Oppel, S., A. Powell, L. Dickson. 2008. Timing and Distance of King Eider Migration and Winter Movements (Fenología y Distancia de la Migración y Movimientos Invernales de Somateria spectabilis). The Condor , 110(2): 296-305.

Oppel, S., A. Powell. 2010. Age-specific survival estimates of King Eiders derived from satellite telemetry (Estimados de la Supervivencia Específicos de la Edad Derivados Mediante Telemetría Satelital en Somateria spectabilis). The Condor , 112(2): 323-330.

Ouellet, J., C. Vanpe´, M. Guillemette. 2013. The body size-dependent diet composition of North American sea ducks in winter. PLoS One , 8(6). Accessed January 15, 2014 at http://zc9gn3am3j.search.serialssolutions.com/?ctx_ver=Z39.88-2004&ctx_enc=info%3Aofi%2Fenc%3AUTF-8&rfr_id=info:sid/summon.serialssolutions.com&rft_val_fmt=info:ofi/fmt:kev:mtx:journal&rft.genre=article&rft.atitle=The+body+size-dependent+diet+composition+of+north+american+sea+ducks+in+winter&rft.jtitle=PloS+one&rft.au=Ouellet%2C+Jean-Fran%C3%A7ois&rft.au=Vanp%C3%A9%2C+C%C3%A9cile&rft.au=Guillemette%2C+Magella&rft.date=2013&rft.eissn=1932-6203&rft.volume=8&rft.issue=6&rft.spage=e65667&rft_id=info:pmid/23755266&rft.externalDocID=23755266&paramdict=en-US .

Palmer, R. 1976. Handbook of North American birds . New Haven, CT: Yale University Press.

Phillips, L., A. Powell, E. Rexstad. 2006. Large-scale movements and habitat characteristics of King Eiders throughout the nonbreeding period. The Condor , 108(4): 887-900.

Phillips, L., A. Powell. 2009. Brood rearing ecology of King Eiders on the North Slope of Alaska. The Wilson Journal of Ornithology , 121(2): 430-434.

Phillips, L. 2005. "Migration ecology and distribution of King Eiders a Thesis" (On-line). Accessed January 18, 2015 at http://www.arlis.org/docs/vol1/D/62235434.pdf .

Schiller, E. 1955. Studies on the helminth fauna of Alaska. XXIII. Some Cestode parasites of eider ducks. The Journal of Parasitology , 41(1): 79-88.

Sittler, B., O. Gilg, T. Berg. 2000. Low abundance of King eider nests during low lemming years in northeast Greenland. Arctic , 53(1): 53-60.

Suydam, R., D. Dickson, J. Fadely, L. Quakenbush. 2000. Population declines of King and Common Eiders of the Beaufort Sea. The Condor , 102(1): 219-222.

Suydam, R. 2000. King eider: Somateria spectabilis . Philadelphia, PA: The Birds of North America, Inc..

Thompson, D., R. Person. 1963. The Eider Pass at Point Barrow, Alaska. The Journal of Wildlife Management , 27(3): 348-356.

VanCleave, H. 1951. The Ancanthocephalan parasites of eider ducks. Helminthological Society , 18(1): 81-84.

Wilson, H., M. Petersen, D. Troy. 2009. Concentrations of metals and trace elements in blood of spectacled and king eiders in northern Alaska, USA. Environmental Toxicology and Chemistry , 23(2): 408-414.

Alaska Natural Heritage Program. Alaska Species Ranking System Summary Report -King Eider. Anchorage, AK: University of Alaska Anchorage. 2002.

Timson, R.S. Bureau of Land Management and National Oceanic and Atmospheric Administration. Late summer migration at Barrow, Alaska. Vol. 1. Boulder, CO: Environmental assessment of the Alaskan Continental Shelf. 1976.

Dickson, D.L. Canadian Wildlife Service. Seasonal Movement of King Eiders Breeding in Western Arctic Canada and Northern Alaska. Canadian Wildlife Service Technical Report Series Number 520. Edmonton, Alberta: Canadian Wildlife Service. 2012.

Alaska Department of Fish and Game: Division of Subsistence. The subsistence harvest of Black Brant, Emperor Geese, and Eider Ducks in Alasak. 234. Juneau, AL: Alaska Department of Fish and Game: Division of Subsistence. 2002.