[order] Anseriformes | [family] Anatidae | [latin] Polysticta stelleri | [UK] Stellers Eider | [FR] Eider de Steller | [DE] Scheckente | [ES] Eider Menor | [IT] Edredone di Steller | [NL] Stellers Eider

Stellers Eider determination

copyright: Bogabirder

Smallish marine duck with squarish head and angular bill; breeding plumage male unmistakable (in eclipse blackish with white secondary coverts); 1st winter male brown with faint suggestion of male head markings - blackish throat and collar; female red-brown with blue tertials (except 1st winter when brown) and whitish inner webs. Most female-type plumages show pale eye ring. Flight fast with rapid beats; male shows white forewing and trailing edge, female has thin white wing bar and trailing edge. Similar: Best told from other Eiders in non adult male plumage by shape and size supported by various plumage features described above. Hints: Occurs in tight flocks which dive simultaneously, search amongst other eider species away from main range.

Steller's Eiders breed in open tundra. The favoured nesting habitat in the Lena Delta is moss-lichen polygonal tundra which apparently also applies to the Barrow area. In both the Lena Delta and the Barrow area breeding females often place their nests in the territories of breeding Pomarine Skuas Stercorarius pomarinus for protection.

The principal breeding areas for the European winter population of Steller's Eider are thought to be Siberia west of Khatanga River. Breeding on Taymyr was originally demonstrated in 1843. For unknown reasons breeding was not recorded here again until 1990, when two different expeditions found Steller's Eider nests in Taymy. Probable breeding records in Yamal, Gydan (c. 75° E) and Taymyr Peninsulas and 9, 3 and 11 records respectively. On the basis of studies in the eastern part of the Taymyr indications of a dispersed population with a maximum nesting density potential of 1 pair/13.3 kmē. A mean density of 1 pair/10-20 kmē was necessary if the total European winter population was to be breeding on Taymyr. West of the Yamal Peninsula, breeding has been recorded on the Kola Peninsula and in Yugorsk Peninsula in 1994, but breeding on Waigach Island and in Bolschezemelskaya Tundra (55°- 65° E) has not been recorded.
Polysticta stelleri breeds (in trivial numbers) in European Russia, and winters in the Baltic and off the northern coast of Norway, which together account for a tiny proportion of its global wintering range. Its European wintering population is small (as few as 7,700 individuals), but was broadly stable during both 1970-1990 and 1990-2000. Nevertheless, more than 90% of the European wintering population is confined to just 10 sites.
The breeding population in eastern Siberia seems to be concentrated in the large deltas of the major rivers from Khatanga River to Kolyma Delta, such as Lena and Indigirka, but also on the New-Siberian Islands. A survey of breeding waterfowl from Kolyuchin Bay (67° N, 174°30 W) on the Chukotski Peninsula to the Kolyma River Delta in June 1993 found Steller's Eider increasing in numbers going west, with a total estimate of almost 12,000 birds. During a similar survey in 1994 from the Kolyma to the Lena Delta about 160,000 Steller's Eider were estimated. However, very little is known about the actual number of breeding pairs in the core area from the Khatanga River to the Kolyma River. Based on anecdotal information about the abundance of Steller's Eider during the last century has found indications that up to 1 million birds occurred in Siberia. The estimated decrease in the world population from 500,000 or 400,000 (Palmer 1976) to the current 220,000 is probably reflected by the trend in numbers in eastern Siberia because the majority of the world population breeds there.

The eider's diet varies between the wintering, marine environment and the summer, breeding, tundra environment. During spring migration and early breeding season, eiders feed by dabbling, headdipping, and up-ending on freshwater shallow. According to researchers, broodrearing females dive for food in the deepest centers of the pond, leaving shallow sides of the same ponds for ducklings to forage. As foraging strategies change with the site and season, so does the diet of the eider. During the breeding season eiders feed primarily the larvae of aquatic flies and plant materials, in addition to crustaceans and mollusks. Freahwater crustaceans (such as gammarid amphipods) and worms may also be a main component of the diet in some portions of the eider's breeding range. In both the Lena Delta and the Barrow area breeding females often place their nests in the territories of breeding Pomarine Skuas Stercorarius pomarinus for protection.
In Siberia, extensive feeding on Chironomid and Tipulid larvae has been reported in June. The same food items were reported for a breeding female from Barrow, June 1991. From the summer diet, Amphipods, Bivalves and Barnacles (Balanus spp.) have been recorded. The feeding ecology was studied during moult at Nelson Lagoon in Alaska from May to October. The birds fed at low tide irrespective of the time of day. Diving took up 80% of the feeding time and up-ending 20%. The diet consisted mainly of molluscs and crustaceans with no difference between age or sex classes. In winter, the birds concentrate in a few coastal areas in Europe usually feeding in water depths of a few metres though occasionally up to 10 m. In Norway, birds selected gently sloping coastal profiles and the majority fed within 200 m of the coast. The food items include molluscs (especially bivalves such as Mytilus edulis and Modiolula phaseolina), crustaceans and polychaetes. In Norway, diurnal cyclical feeding was observed throughout most of the tidal cycle. Roosting only occurring at high tide. Steller's Eider at Vadso Harbour (70°04 N, 29°45 E), Norway, fed by diving offshore on ebb and flow tides. They resorted to algal beds (where they appeared to be gleaning gastropods) as they were exposed on the falling tide and fed by dabbling in sandy-mud beach substrate at low tide. Diurnal feeding has also been reported from Sweden.

This species has been uplisted to Vulnerable as recent evidence suggests that it is undergoing a rapid population reduction, particularly in the key Alaskan populations. However, further information is needed on whether declines might reflect population shifts; if so, the species may warrant downlisting. [conservation status from birdlife.org]

Eiders nest on tundra adjacent to small ponds or within drained lake basins. Nests are a shallow depression on the ground, amongst moss or sedge vegetation. The nest is lined with a thick bed of down, mixed with breast feathers and bits of vegetation. Many nests are partially or completed destroyed from predation by foxes, ravens, jaegers, or other predators.
Eggs are olive buff, mottled with darker shades. They are approximately 2.4 inches (61 mm) long The most common clutch sizes at Barrow are 5 or 6 eggs, but range up to 8. Only the female incubates, and for 24 days she remains on the nest, taking a few short breaks (under an hour) each day to feed. Males may remain near the nest during early incubation, but in general they become decreasingly associated with nest sites and females after the onset of incubation. Most males leave the breeding areas by early July.

Migratory. Main wintering area southern Bering Sea, where all Alaskan breeders and most from north-east Siberia winter. Some birds migrate west to northern Norway, north-west Russia, and Baltic Sea. Arrive Baltic Sea October-November, numbers gradually increasing during winter, and leave again early or mid-April.

In Lithuania, the departure takes place in April although a few birds remain until the middle of May. The wintering quarters in Estonia are left in May and in the Gulf of Finland (c. 60° N, 25-30° E), up to 3,000 Steller's Eider migrate east or north-east in the first half of May. Concurrently with the population increase the timing of the passage has become earlier. Median date of the migration is now 7 May in the central Gulf of Finland compared to a 16 May in the 1980s. In Varangerfjord, the majority of birds depart in May though small flocks may stay throughout the summer. In east Asia the spring migration starts in March peaking in Kamchatka in the middle of May and in Alaska it starts in April peaking in the beginning of May.
In Norway the first birds arrive to the winter areas in October with numbers building up throughout the winter. The arrival of the first birds in Estonia most often takes place in November, while the birds which reach Lithuania in December build up to a maximum in January/February. Northerly wintering seaducks like Steller's Eider are dependant on open water for feeding, hence their distribution in late autumn and winter is influenced by the extent of the sea ice in staging and winter areas.