Common Eider

The Common Eider is the largest duck in the Northern Hemisphere, a bulky, thick-necked sea duck built for life in cold, wave-battered coastal waters. Its distinctive sloping profile, created by a long bill that merges smoothly into a wedge-shaped forehead, is a key identification feature at any distance.

Breeding males are bold and unmistakable: a mostly white body and back, black belly and flanks, a black cap, and a soft pale green wash on the nape, with a pale peach-tinted breast. Females are entirely different, cloaked in dense, intricately barred brown and black plumage that provides excellent camouflage on the nest.

Common Eiders are famous for their down feathers, which have exceptional insulating properties.

Key field marks

• Large, heavy body with a distinctive sloped forehead-to-bill profile
• Breeding male: black-and-white body, black cap, pale green nape patch
• Female: dense brown barring overall, no bold pattern
• Low, direct flight in lines over the water, often close to the surface

Similar species

• King Eider: Breeding males have an orange knob at the base of the bill and a gray-blue crown rather than the Common Eider's smooth sloping profile; females are similarly barred but show a more rounded head shape and shorter bill.
• Scoters: Female eiders can suggest female scoters but are larger, bulkier, and show the characteristic sloped bill profile.

Common Eiders inhabit cold coastal and marine waters across the Arctic and subarctic regions of North America, Europe, and Asia, nesting colonially on rocky islands, coastal tundra, and offshore skerries close to productive shellfish beds.

Outside the breeding season they remain almost entirely marine, gathering in large rafts in nearshore waters, bays, and around rocky headlands, generally staying close to shore rather than moving far inland.

Behavior

Common Eiders are highly social, nesting in dense colonies and forming large flocks at sea, sometimes numbering in the thousands. They dive to the seafloor to pry mussels and other shellfish loose, swallowing them whole and crushing the shells in a muscular gizzard.

Voice

Males give a distinctive, far-carrying crooning "ah-ooo" call during courtship displays; females give lower, harsher grunting and cackling calls.

Feeding

They feed by diving to the seabed for mussels, clams, and other mollusks and crustaceans, often in relatively shallow nearshore waters.

Nesting and breeding

Females nest on the ground, often in dense colonies on predator-free islands, lining the nest with copious amounts of soft down plucked from their own breast. They lay 3-6 eggs and incubate alone, fasting for much of the incubation period.