Common Eider

The Common Eider is a heavyset, thick-necked sea duck of northern coastlines, famous for the soft down feathers females use to line their nests. Breeding males are boldly patterned: a white back and breast, black belly and flanks, a black cap, and a pale mint-green wash on the nape, with a distinctive sloping profile created by the bill running smoothly into the forehead. Females are warm brown, densely barred all over for camouflage on the nest.

As the largest duck in the Northern Hemisphere by bulk, the Common Eider is built for a life on cold, rough seas, riding low and buoyant on the waves and diving to pry mollusks from rocky or sandy seabeds.

Key field marks

• Large, bulky body with a distinctive wedge-shaped head profile where the bill slopes directly into a flat forehead
• Breeding male: white chest and back, black belly, black cap, pale green nape patch
• Female: warm brown with fine dark barring overall, same sloped head/bill shape
• Flies low over water in long lines with slow, steady wingbeats

Similar species

The King Eider male has a gray-blue head, orange bill shield, and black (not white) back, quite different overall; female King Eiders are more rufous and less coarsely barred than female Common Eiders, and have a shorter bill without the sloped profile.

Common Eiders breed colonially along rocky and sandy Arctic and subarctic coastlines around the Northern Hemisphere, nesting on islands and sheltered shorelines close to the sea. They are highly marine, rarely straying far from salt water, and winter in large rafts on nearshore ocean waters, bays, and ice edges where mollusk beds remain accessible.

Behavior

Eiders dive to the seabed to pry loose mussels and other shellfish, swallowing them whole and crushing them in a muscular gizzard. They often gather in large, dense flocks on the water.

Voice

Males give a distinctive, far-carrying moaning "ah-OOO" during courtship; females give low, guttural quacks.

Feeding

Mussels and other mollusks form the bulk of the diet, along with crustaceans and echinoderms, obtained by diving in nearshore waters.

Nesting

Nests in dense colonies on coastal islands and tundra; females line the nest with their own soft breast down, and incubate alone for about 24-26 days, fasting for much of that time.