Polysticta stelleri

Only member of genus Polysticta. Member of the monophyletic group of diving ducks (Anatidae).

This duck has suffered a precipitous population decline of unknown cause since the 1960s and local extinction of some breeding populations. Discontinuous, reduced breeding range in northern coastal Alaska and along the arctic coast of Russia. Total population size is about 140,000.

Three breeding populations are recognized: two in Russia and one in Alaska. The Russian-Pacific population occurs along the Arctic coast of Siberia from the Chukotski Peninsula west to the Kheta/Khatanga River (Bering Sea wintering population) and the Russian-Atlantic population occurs along the Arctic coast of Siberia west of the Khatanga River (European wintering population) (Pihl 1999, Fredrickson 2020). In Alaska, the species breeds on the Arctic Coastal Plain and on the Yukon-Kuskokwim Delta (USFWS 2002, Fredrickson 2020).

Birds from the Alaska breeding population and the far more abundant eastern Siberia population molt and winter mainly along the Alaska Peninsula. Thousands also spend late summer off the coast of St. Lawrence Island, especially along the north coast; they are fairly common in shallows east of Gambell and at the Pribilof Islands, especially St. Paul Island (Alison 1994). Eastern Siberian breeders also molt in Kamchatka and winter in the southern Bering Sea and Northern Pacific Ocean, primarily on the Commander and Kurile Islands; and in small numbers off Japan (Pihl 1999, USFWS 2002).

Western Siberian breeders molt and winter in the Barents and Baltic Seas (Pihl 1999). Surveys in 2009 found that 85 percent were wintering in Russian waters, up from 30-50% in the mid-1990s; the difference probably a result of climate change (Aarvak et al. 2013, Fredrickson 2020).

The number of distinct occurrences (subpopulations) has not been determined.

Causes for the population decline are unknown. Climate change, changes in predator-prey relationships, fisheries bycatch, changes in the marine ecosystem, overharvest, lead poisoning, and disturbance have all been cited as possible factors (BirdLife International 2018).

As early as 1997, climate change (with associated changes in food availability and trophic structure) was recognized as a threat to this species (USFWS 1997). Reduction of sea ice extent and thickness may affect eiders in unknown ways (BirdLife International 2018) and on land, climate warming is causing the loss of Arctic tundra ponds through permafrost melting (Andresen and Lougheed 2015). Increased predation may also result from climate-related collapses in the pattern of rodent population cycles, causing predators to seek out alternative prey (Quakenbush et al. 2004, Iles et al. 2013).

Bycatch in gillnet fisheries is another recognized threat, as is resource competition from shellfisheries (Dagys and Žydelis 2002, Skov et al. 2011, Žydelis et al. 2013).

Foxes were suspected to be responsible for the failure of 44 percent of Steller's Eider nests studied near Barrow from 1991 to 1995 (Quakenbush and Suydam 1999). Populations of certain predators, such as Arctic Foxes and Common Ravens are increasing due to increased human settlement and subsequent increased food supply in the form of refuse or handouts (USFWS 1997, 2002).

On land, lead poisoning of nesting waterfowl still occurs. A study in Alaska found lead shot ingestion to be an important source of mortality for breeding Spectacled Eiders (Somateria fischeri). Similar habitat use between the two species suggests that lead poisoning may be a contributing factor to the long-term decline in the Alaska-breeding population (Flint and Herzog 1999). Breeding populations are also potentially threatened by oil and gas exploration, development and disturbance (USFWS 1997).

Large concentrations of birds during molting, migration, and wintering are vulnerable to oil and other marine pollution. In Europe, many have been killed in several oil spills, and major oil terminals exist and are planned immediately adjacent to wintering sites (Pihl 1999). These concentrations also are vulnerable to disturbance from human activities.

Subsistence and illegal harvest may impact Asian breeding populations, but the influence on U.S. populations is minimal (Solomonov 1987, Pihl 1997).

The small, geographically restricted breeding population in Alaska may be vulnerable to depletion by disease. Recent sampling has indicated that exposure rates to a virus in the family Adenoviridae may be a potential threat (Hollmen and Franson 2002).