A large, powerful, fast-flying diving duck of coastal waters. Females dark and closely barred all over, males strikingly contrasted, beautifully clean and neat; the wedge-shaped face is distinctive. 

Eiders are often found in flocks well offshore, yet they are much more likely to be seen pottering about in harbours, at the mouths of estuaries, or around the myriad rocky islets, headlands, and weedy bays. They are sociable, unhurried, unflappable. Their plumage variations are complicated so they are always interesting to look at, but it is the colours and calls of the drakes and confiding behaviour of the ducks that makes them such enjoyable birds to watch.