Steller's eider (Polysticta stelleri)

Steller's eider (Polysticta stelleri) (photo: NBIC)

Barents sea region red-listed species
Typography
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The smallest of eiders (body mass 750–850 g, wingspan 70–76 cm), the Steller’s eider has morphological and behavioural similarity to dabbling ducks. A compact duck with small, thick-based, slightly drooping bill and steep forehead and nape. Sexually dimorphic, but both sexes has distinctive bluish speculum bordered with white. Alternate (breeding)-plumage of males is striking, with white head and large white shoulder-patch contrasting with chestnut breast and

belly, distinctive black spot surrounding eye. In basic plumage male resembles female, which has dark-brown mottled plumage, but upper wing-coverts remain white in males. Highly social when nonbreeding, regularly occurs in large flocks. Synchronous diving is noticeable.

Steller’s Eider has semi-circumpolar range restricted to the coastal areas. Two flyway populations are recognized: an Atlantic one breeding in Western Russian Arctic, and wintering in N Europe and a Pacific population breeding in Eastern Siberia, Chukotka and Alaska, and wintering in N Pacific. Steller’s eiders from the entire Atlantic population inhabit Barents Sea Region all-year-round and have principal wintering grounds from Finnmark to Tersky Coast of the White Sea, spring staging grounds off W Novaya Zemlya, Murman Coast and Kanin Nos Cape, moulting and autumn staging off Novaya Zemlya, in the Pechora Sea, and off mainland coast from Tersky Coast to Finnmark (Aarvak et al. 2012, Krasnov et al. 2004, 2005, Petersen et al. 2006). Breeding population in Barents Sea Region is very small with broods occasionally reported from Yugorsky Peninsula and historically from E White Sea, scattered nesting on Vaigach and W Novaya Zemlya is supposed from satellite data (Petersen et al. 2006).

Key habitats - seasonality

Steller’s eiders nest on coastal tundra plains near freshwater bodies but shifts to shallow marine waters once breeding is completed. Migrate over sea, both along the coast and offshore, but often overfly land. Only breeding females and broods forage on tundra ponds. While at sea inhabits the littoral zone in various inshore habitats, frequenting bays and river mouths (del Hoyo et al. 1992). Forages in kelp forests in shallow waters and particularly favours brackish water areas. In Finnmark, small harbours are commonly used. Along Kola Peninsula and in Novaya Zemlya occurs on shallows both off open rocky coasts and in skerries. During winter may reside in polynyas in the White Sea (Aarvak et al. 2012), some birds reaching Kandalaksha Bay (Krasnov & Goryaev 199*).

Biology – migration, life strategy, feeding, trophic relation, etc.

Typical seaduck, keeps to the seas outside breeding season. Similar to all diving ducks is a long-lived bird with delayed maturity, relatively low reproductive rate and on average a high ratio of adults in the population.
Breeding starts in June, nesting in within the region found single pairs, but in Siberia may nest in small colonies of up to some tens pairs. Breeding performance is highly dependent on season conditions, and particularly predation by skuas and Arctic foxes which in turn governed by lemming cycles (). Clutch is 5–7 eggs, incubation takes 26–27 days, hatching occurs in mid-July.

When at sea, feeds chiefly on molluscs, crustaceans and other marine invertebrates (Bustnes & Systad 2001). During moult, bivalve molluscs are the primary food source (Petersen 1981). Forages by diving to a depth of less than 10 m or by up-ending and head submerging.

Steller's Eider is a typical long-distant migrant within Arctic and sub-Arctic regions. Summer migration of males, nonbreeding and failed-breeding eiders starts already in July. Stopovers are known from Pechora Sea, west Novaya Zemlya and eastern Murman coast.

The Barents and Baltic Sea coasts represent wintering areas (from late autumn to April). Spring migration begins in April, usually peaking in May (Kear 2005). Arrive on the breeding grounds since early June. Nonbreeding birds remain in wintering quarters in Varangerfjord and off E Kola Peninsula.

Population status – numbers and trends

Wintering population in North Pacific was slightly above 74,000 birds in 2011 (Larned 2012), and population is continuing to decline (BirdLife 2013).

Wintering populations in Europe (including Russia) were estimated at 23,060–36,160 individuals. In Europe, marked declines have been noted in recent years, with numbers falling by an estimated 13% per annum in the Baltic between 1994 until 2003 and by 8% per annum in Norway between 1985 and 2003 (Žydelis et al. 2006). The decline in the Barents Sea has recently been re-evaluated by Aarvak et al. (2012) based on a new survey in 2009. The reassessment/number of wintering birds in 2009 was at the same level as in mid-1990s, i.e. ca. 27,000 individuals. There is a major redistribution of birds from Varanger to the Kola Peninsula waters, where about 85% of the population winters now.

Threats – natural and anthropogenic

It is not currently clear which of these many factors is driving the overall decline (K. Laing 2004, Žydelis et al. 2006). , but see Aarvak et al. 2012).

Nest and bird predation by mammalian and avian predators shown to be a threat for the Pacific population (Safine 2011). Predation by arctic foxes, skuas and larger gulls may account for as high as 15% loss of adults during incubation period (Solovieva 199*). In low lemming seasons, Steller’s eiders may completely fail their breeding. Increasing human habitation of Arctic regions has increased the range and numbers of e.g. large gulls, leading to a greater risk of predation (Kear 2005).

Climate change and associated changes in sea ice may affect eiders in unknown ways. Habitat loss due to reduced occurrence of kelp forest in Varangerfjord may be a key factor for wintering distribution in the Barents Sea.

Among anthropogenic threats, the overfishing, petroleum exploration, production and transportation in shelf areas, as well as oil spills are considered the most important source of negative impact (Bustnes 1997, Gavrilo et al. 1998, Hario 1997, Svazas 1997). Individuals were killed by oil spills at an important wintering area in Varangerfjord, Norway, during 1973, 1979, and 1993 (Bustnes 1997). Entrapment in lost and discarded fishing gear, as well as power line constructions are regarded as local threats in Finnmark (Aarvak et al. 2012).

Subsistence hunting (Solomonov 1987, Pihl 1997a) and exposure to lead shot and subsequent lead poisoning (Grand et al. 1998), are considered negatively affecting Pacific population of Steller’s eiders. Illegal hunting on the breeding grounds is assumed to be the issue for Atlantic population as well (Pihl 1997b).

Conservation measures and needs

Circumpolar Eider Conservation Strategy and Action Plan was developed 1997 by CAFF and European Union Species Action Plan for Steller’s Eider was compiled in 1997 (Pihl 1997b).

Taking into account booming petroleum industry development on the Arctic shelf and international importance of nonbreeding grounds of the Steller’s eiders in the Barents Sea Region, protection of key marine habitats of the Steller’s eiders appears to be an urgent measure.

The following Conservation priorities were listed

Locate and assess status of breeding and moulting sites - high

Remove current threats from sites - essential

Conserve and manage major sites - essential

Research and monitor population numbers through annual cycle - high

Use satellite tracking to locate breeding and moulting sites - high

Locate and assess key breeding and moulting areas - high