Steller's eider (Polysticta stelleri) is a migratory Arctic sea duck that breeds along the coastlines of Russia and Alaska, as well as in the Baltic Sea. It is the smallest, and fastest flying of the duck species known as eiders; it is closely related to the other species of eider in the genus Somateria, but sufficiently distinct to be given separate recognition as the only member of the genus Polysticta.
Due to the extensive contraction of its breeding range, the Alaska-breeding population of Steller's eider was listed as vulnerable in 1997 by the International Union for the Conservation of Nature (IUCN). The species is protected in Estonia, Finland, Norway, Russia and the United States, and is the subject of an ongoing recovery plan by the European Union and U.S. Fish and Wildlife Service. 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, with no subspecies being recognised. The genus name is from Ancient Greek meaning "much spotted" (from "many" and "spotted").
Steller's eider was separated from the other eider species into its own genus in 1945 due to behavioural and anatomical differences. Genetically, it is however closely related to all other extant eider species in the genus Somateria. Its closest relative was the now-extinct Labrador duck Camptorhynchus labradorius, but with these two species next closest to the genus Somateria; They have a compact body with a relatively large head with a flat crown and an angled nape, and a long, thick bill; the tail is relatively longer than other eiders. The males assume their breeding plumage from early winter to midsummer with a black cap, chin, collar, eye-ring, and rump, with a white head and shoulders, light green patches behind the head and in front of the eye, and the cinnamon breast and shoulders marked with a prominent black spot.
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Habitat and distribution
thumb|Marshy tundra, Alaska, USADuring the winter, Steller's eiders occupy coastal bays and lagoons that offer suitable forage while occasionally feeding in deeper waters that remain adequately sheltered.
Population distributions
There are three recognised breeding populations of Steller's eiders, one in Alaska and two in Arctic Russia.
- The Russian-Atlantic population breeds west of the Khatanga River in western Siberia, and winters in the Barents and Baltic seas.
- The Russian-Pacific population breeds east of the Khatanga River, and winters in the southern Bering Sea and northern Pacific Ocean. 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. While in the tundra during the summer months, they feed on aquatic insects and plant material such as crowberries and pondweeds.
Females establish their nests in marshy tundra close to permanent open water that has additional access to small ponds. The young are precocial and hatch between late June and late July with their eyes open and sporting downy feathers. Notably, the males court the females in silence. Since their listing, additional threats such as exposure to oil and other contaminants have been identified. Climate change has also been implicated in the collapse of rodent populations, forcing predators to exploit alternative prey such as the eggs and young of Steller's eider. Further studies have also shown that lead concentration was higher in individuals located close to industrialised regions than non-industrialised regions.
Nest predation
Nest predation by the Arctic fox, pomarine jaeger, snowy owl, and common raven pose the greatest threat to Steller's eider nesting success rates.
Natural resource exploitation
The exploitation of natural resources such as oil and gas contributes to Steller's eider habitat loss. Many recent studies have reported prominent infection rates amongst Steller's eiders in Alaska, ranging from 0.2% to 5%. It has been suggested that 80% of Steller's eiders in Alaska have antibodies to avian influenza.
Recovery plan
Two recovery plans have been implemented to restore healthy populations of Steller's eiders. The European Union action plan, The entire designation includes approximately and of coastline. Egg collection and subsistence hunting still occurs in Alaska, but is uncommon. The degree of subsistence hunting in Russia and its effect on the population is poorly documented.