Common Eider

Identification

The drake is one of the most striking sea ducks: white back and breast, black belly and rear, a black cap, a pale green nape and a wedge-shaped bill that slopes smoothly into the forehead with no sharp angle. Females are warm rufous-brown with dense dark barring and a distinctly concave bill profile, which is the surest way to separate them from other female sea ducks. Males moult into a dark eclipse plumage in summer and look drab for several weeks.

Eiders are diving ducks that feed on mussels, cockles and crabs, swallowing them whole and crushing the shells in a muscular gizzard; a dive can last around a minute. They nest colonially on rocky islands, often beside gulls and terns whose alarm calls add protection, and the female lines the nest with down plucked from her own breast — the original source of eiderdown. Ducklings leave the nest within a day and gather into crèches tended by a few females.

Look for them on cold northern coasts, in harbours and off estuaries, where flocks raft offshore and fly low over the waves in lines. Winter is the season for inshore viewing, while in spring the males' moaning display calls carry right across the colony. A telescope helps, and a seawatch in a stiff onshore wind often pushes birds close to shore.