Common eider (Somateria mollissima)

Description and characteristics

Common eiders are robust, heavy-bodied ducks with relatively short wings and a thick bill. Males in breeding plumage are mostly white with contrasting black markings, while females are mottled brown and well camouflaged. Both sexes have dense, waterproof feathers and a layer of down beneath the contour feathers that provides insulation in cold water. They dive from the surface to forage, commonly pursuing clams, mussels, crustaceans and other benthic invertebrates.

Distribution, habitat and movements

Breeding populations occur along the northern coasts of Europe, across Arctic and subarctic parts of North America, and in eastern Siberia. During winter they move to more temperate coastal waters where they may form large, often conspicuous flocks over sheltered bays and estuaries. For general information about sea ducks see sea ducks; regional overviews include Europe, North America, and eastern Siberia, with breeding concentrated in the Arctic and nearby zones.

Breeding and human use

Eiders nest colonially on islands and sheltered coasts. Females build shallow bowls lined with their own down, which they pluck from their breast to insulate eggs and chicks. Because eiderdown is exceptionally warm and lightweight, people in a number of coastal communities have historically collected down from wild nests or from managed nesting sites; such harvesting, when carefully regulated, can be sustainable and forms part of local tradition.

Behavior, ecology and conservation

• Feeding: mainly benthic; eiders dive repeatedly to gather shellfish and crustaceans.
• Social life: often gregarious outside the breeding season, forming flocks on the sea.
• Flight: capable of rapid flight over open water (recorded top speeds are high for ducks).

Global assessments list the common eider as of relatively low extinction risk, but regional trends vary. Local declines have been linked to oil pollution, disturbance at colonies, increased predation and changes to marine food supplies associated with warming and human activities. Conservation measures focus on protecting key nesting areas, reducing pollution, and maintaining traditional, sustainable harvest practices where they exist.