Common Eider: where and when to see them

The common eider is a heavily built sea duck of northern coasts, famous for the insulating down females use to line their nests. Adult males show bold black and white plumage with a greenish nape, while females are intricately barred brown. Its sloping forehead and substantial bill create a distinctive profile. Although widespread, the species faces regional declines linked to changing food supplies, disturbance, disease and other pressures.

Size

50-71 cm long

Weight

1.2-2.8 kg

Lifespan

10-20 years

Status

Near Threatened

Eiders gather in coastal flocks, often feeding where shallow seabeds support abundant shellfish. Courtship includes soft, resonant male calls and conspicuous head movements. Females nest on the ground, sometimes in loose colonies, and may lead ducklings into communal broods attended by several females. Outside breeding, birds concentrate in moulting or wintering areas. Flight is strong and direct, usually low over the sea with relatively rapid wingbeats. Common Eiders are renowned for their exceptionally insulating down, which females use to line their nests. During courtship, males perform a distinctive 'cooing' call, often accompanied by head-tossing displays. Outside the breeding season, eiders are highly social, forming large rafts for mutual protection and foraging efficiency.

• Females pluck breast down to line and cover their eggs.
• Ducklings may join communal broods called crèches.
• Adults can swallow mussels whole.
• Traditional eiderdown collection depends on nest material rather than plucking living birds.

Northern breeding coasts are most accessible from late spring through summer, when females and broods may be present. In New England, colder months often bring larger coastal concentrations. Timing varies with latitude and ice conditions, so Arctic travel windows are not interchangeable with southern winter viewing. In the Arctic, eider viewing is best during the short summer when sea ice has retreated and breeding colonies are active. Migratory movements are significant, with birds often travelling hundreds of kilometres between breeding and wintering grounds. Winter aggregations in Norway can be spectacular, especially in ice-free fjords and archipelagos.

Rocky shores, sheltered bays, offshore islands and shallow coastal banks are typical habitats. Breeding females need secure ground close to the sea, often among vegetation or rocks. Winter flocks favour productive marine feeding areas rather than inland freshwater lakes. Eiders are highly gregarious outside the breeding season, forming large rafts offshore in areas with abundant food. While generally coastal, they may venture several kilometres offshore to feed in suitable areas. They are highly adapted to cold water environments due to their dense plumage and large size.

Mussels and other marine molluscs are major foods, supplemented by crabs, sea urchins and additional bottom-dwelling invertebrates. Many prey items are swallowed whole and crushed internally. Accessible shellfish beds strongly influence where feeding groups gather and how they move with tides. Their strong, wedge-shaped bill is specifically adapted for plucking shellfish from rocks and the seabed. Eiders have a gizzard well-suited for grinding tough mollusc shells internally. They typically forage by diving to the seafloor, often in depths up to 20 meters.

Common name

Common Eider

Scientific name

Somateria mollissima

Animal group

Birds

Size

50-71 cm long

Weight

1.2-2.8 kg

Lifespan

10-20 years

Status

Near Threatened

Identification

Its long, wedge-shaped head distinguishes it from king eider, whose adult male has a conspicuous orange forehead shield. Adult males are unmistakable with their black and white plumage, green nape, and yellow-orange bill. Females and immatures have cryptic brown plumage but can be identified by their distinctive head shape and larger size compared to most other sea ducks. In flight, their large size and direct, powerful wingbeats are characteristic.