Steller's Eider

识别特征

Steller’s eider is the smallest of four eider species, with both females and males weighing 800 grams on average (1.8 pounds). They have a compact body with a relatively large head, long tail, and a long, thick bill. The males assume their breeding plumage from early winter to midsummer with a black cap, chin, throat, eye-ring, and rump, with a white head and shoulders, light-green patches behind the head and in front of the eye, cinnamon breast and shoulders marked with a prominent black spot. The wings appear to be striped white, with an iridescent bluish-purple background colour and white border. They have palmate feet (3 fully webbed toes) which are a dark bluish-gray, the same color as the legs. In mid-summer to fall, males assume their non-breeding plumage which is primarily dark brown with a white-bordered bluish speculum (secondary feathers) on their wing. Females are a dark to cinnamon brown with a pale-white eye-ring, similar to the lighter brown juveniles. Females also have iridescent bluish-purple speculums with a white border running the entire length of the secondaries.

分类信息

Steller's eider was formally described and illustrated in 1769 by the German naturalist Peter Simon Pallas from a specimen collected on the Kamchatka Peninsula in Eastern Russia. He coined the binomial name Anas stelleri; the specific epithet was chosen to honour the German naturalist and explorer Georg Wilhelm Steller. Steller's eider is now the only species placed in the genus Polysticta that was introduced in 1836 by the English naturalist Thomas Eyton. The species is monotypic: no subspecies are recognised. The genus name is from Ancient Greek polustiktos meaning "much spotted" (from polus "many" and stiktos "spotted").<p>Despite its name, it is only distantly related to all other extant eider species, which are part of the Somateria genus. Steller's eider was separated from other eider species into its own genus in 1945 due to behavioral and anatomical differences. Accordingly, Steller's eider may provide a taxonomic link between the eider species in the Somateria genus and the other sea ducks. It is most closely related to the extinct Labrador duck.

学名

Polysticta stelleri

命名信息

(Pallas, 1769)

目

Anseriformes

科

Anatidae

属

Polysticta

分布与栖息地

During the winter, Steller’s eiders occupy coastal bays and lagoons that offer suitable forage while occasionally feeding in deeper waters that remain adequately sheltered. They nest in marshy tundra along the coast, in areas dominated by water sedge and pendant grass. Within the marshy tundra, they designate specific areas to build their nest, preferring elevated surfaces covered by shallow vegetation such as mosses and grasses. Their molting habitat consists of relatively shallow coastal lagoons that offer viable eelgrass and tidal flats for foraging and beaches and sandbars to rest while they remain flightless.<p>There are three recognized breeding populations of Steller’s eiders, one in Alaska and two in Arctic Russia.<p>Some non-breeding populations will also spend their summers in northern Norway, on the east coast of Russia and adjacent waters, and south-west Alaska.

繁殖区

NA, PAL : nw, ne Siberia from Yamal Pen. to Chukotka; and Arctic Coastal Plain, n Alaska

非繁殖区

to Kamchatka Pen., Commander and Kuril is. (se Russia) and Aleutian Is.; also Kola Pen., Barents and White seas (nw Russia) and Baltic Sea

迁徙

Complete migrants

行为

Steller's eiders forage primarily near the shore by employing various techniques such as briefly diving and swimming underwater (to a maximum depth of 9m), wading and dabbling. They feed by surface techniques more than other sea ducks and prefer relatively small prey. Studies have shown that Steller's eiders are specialists in catching highly mobile prey but may limit their diet to crustaceans even when higher energy sources, such as capelin, become available. This discrepancy in food preferences may be due to their inability to exploit deeper habitats. Steller's eiders also feed on mollusks, echinoderms, polychaete worms, and mussels during the winter. While in the tundra during the summer months, they feed on aquatic insects and plant material such as crowberries and pondweeds.<p>According to banding studies, Steller's eiders can live up to 21 years and four months and reach sexual maturity at two years. Males engage in leks on the wintering and breeding grounds, where groups of males attempt to win over an individual female with elaborate displays. Males court females in silence by displaying a consistent sequence of side-to-side head-shaking while swimming towards and away from their potential female partner. Steller's eiders tend to form breeding pairs during late-winter to early-spring instead of the fall like most waterfowl. Breeding pairs arrive at their nesting sites as early as the beginning of June.<p>Females establish their nests in marshy tundra close to permanent open water that has additional access to small ponds. They specifically select mounds or ridges dominated by mosses, lichens, and grasses. Their nest is shallow, lined with grasses, moss, lichens, and down feathers plucked from the female's breast, who builds the nest without help from the male.<p>Females usually lay 1-8 olive to brownish-orange eggs per breeding cycle. She then incubates the eggs alone for about 25 days. The young are precocial and hatch between late June and late July with their eyes open and sporting downy feathers. However, predators consume the majority of eggs before they are hatched. The young go to the water shortly after hatching and immediately feed themselves, without relying on their mother for food. Regardless of their feeding independence, females will stay within 700m of their nest for up to 35 days post-hatch, while the young begin flying approximately 40 days after hatching. It is not uncommon for one female to assume care of two or more sets of young from a different mother.<p>Males make a low jumbled growling sound, while females make a discrete qua-haaa sound of a similar tone. Males have also been reported to produce a repetitive crackling sound when females go underwater. Notably, the males court the females in silence. During flight, their feathers produce a mechanical whistling sound.<p>After breeding, Steller's eiders gather in high-density flocks to synchronously molt (replace all their feather at the same time) in Arctic lagoons in northwest Asia and along the Alaska peninsula. They remain flightless for about three weeks, but the entire flight-feather molt lasts from July to October. Juveniles molt first, followed by adult males and adult females.

保护状况

In 2016, the global population of Steller’s eider was estimated at 110,000-125,000 individuals and classified as vulnerable by the International Union for the Conservation of Nature (IUCN).<p>In 1992, the U.S. Fish and Wildlife Service reviewed the status of Steller’s eider and concluded that listing the species as endangered was warranted, but precluded by higher species listing priorities. One year later, in 1993, they reconsidered Steller’s eider’s status and supported the listing of the Alaska-breeding population, but did not include the Russian-breeding populations. Finally, the Alaska-breeding population was listed as threatened in 1997. The primary reason for listing was the near disappearance of the Yukon-Kuskokwim Delta population, contracting the Alaskan nesting sites to the Arctic Coastal Plain and increasing the population’s risk of extirpation.`

种群趋势

declining