Common Eider

The common eider (Somateria mollissima) is the largest duck found in the Northern Hemisphere. It is found across the northern coasts of Europe, North America, and eastern Siberia, preferring cold maritime environments. Adult males are striking with their black and white plumage and a characteristic green nape, while females are mottled brown, providing excellent camouflage. Typically, males are larger, reaching up to 70 cm (28 in) in length with a wingspan of about 96 cm (38 in). The species can weigh between 1.5 to 3 kg (3.3 to 6.6 lbs). Male are easy to distinguish from other species by their unique coloration, but the females are best separated from other ducks by the distinctive shape of their bill.

Common eiders are coastal birds, usually found in marine environments such as rocky shores, sandbars, and islands. They primarily feed on mollusks, crustaceans, and sea urchins, with a particular preference for mussels. Eiders dive to the seafloor to forage, using their strong, thick bills to break open shells. They are also known to consume other small marine invertebrates and occasionally plant matter.

This species is partially migratory. Northern populations tend to migrate southward during the winter to avoid ice-covered waters, moving to more temperate coastal areas. They typically migrate in large flocks, often forming V-shaped formations in flight. Migration timing varies with latitude but generally occurs in late autumn and early spring.

The breeding season for common eiders starts in late spring. Females build nests close to the shore, often on islands to avoid predators, using down feathers plucked from their own bodies to line the nest. After laying an average of four to six eggs, the female incubates them for about 24-26 days. During this period, she rarely leaves the nest and relies on her fat reserves. After hatching, the ducklings are precocial, meaning they are relatively mature and mobile. They fledge within 50-70 days, learning to dive and feed themselves under the guidance of the female. The common eider has a unique communal care system where females sometimes form crèches, combining their broods and taking turns watching over the young while others feed.

The common eider is currently listed as near threatened on the IUCN Red List. While the global population is relatively stable, certain regional populations face significant threats. These include habitat loss due to coastal development, diseases, predation, as well as overfishing and harvesting of mussels, which reduces their food supply. Additionally, climate change poses a long-term threat by altering their marine habitat.