Common eider ducks. Male to the left, 3 females and a chick to the right.
Description: The Common eider is a large diving duck (58 cm long, 1.2-2.8 kg in weight) and can hardly be confused with any other species in Spitsbergen. King eiders are the possible exception, as there may be a pair of King eiders amongst a flock of Common eiders. The females are indeed very similar, so distinguishing female King and Common eiders is rather for the experienced birdwatcher. This is, on the other hand, a marginal problem, as King eiders are quite rare in Svalbard. Within Common eiders, males and females are easily distinguished: The male catches the eye with a contrast-rich plumage, the details of which change with age, whereas the female has a brown camouflage plumage. Distinctive is the shallow forehead, which contrasts with the bulging forehead of the King eider.
Distribution/Migrations: Common eider ducks are widely distributed in the Arctic and sub-Arctic. They spend the winter largely in the breeding areas; only the northernmost populations move further south. Common eiders from Svalbard winter in northern Norway and Iceland. In Svalbard, they breed everywhere in the archipelago in dense colonies on small islands that are inaccessible for Arctic foxes, once the ice is broken up.
Biology: Male and female stay together from autumn onwards and then in many cases for several years, but they do not pair for life. The breeding season starts as soon as the nesting sites are free of snow (late May – mid June). The female builds the nest, a shallow hole in the tundra upholstered with bits of plants and down, and then lays four to six eggs, occasionally even more. Sometimes two females share a nest. The well-camouflaged female sits for 24 to 26 days, living on her fat reserves during this period. The male will stay near the nest to begin with, but then joins other males in larger groups for moulting. As soon as the chicks have hatched, they follow their mother to the water and stay there, near the coast, until late summer or autumn.
A typical system for raising the offspring is the formation of a “Kindergarten” (creche) where a few females take care of a large group of young birds.
Miscellaneous: The Svalbard population is estimated at somewhere between 13,500 and 27,500 breeding pairs, not including non-breeding individuals and young birds. In the early 20th century, trappers collected down from the nests, which is still being done in so-called “Eider-farms” in Iceland and, to a very limited degree, in Spitsbergen. Provided it is done carefully, it does not do any harm to the adults or the eggs. Nowadays, Common eiders are protected, and most of their important breeding islands have been declared bird sanctuaries where all traffic is generally banned during the breeding season. Many eggs and chicks fall victim to Glaucous gulls and Arctic foxes. Polar bears that are “stranded” on islands with Common eider colonies will live on scrambled eggs for several weeks, reducing breeding success to zero.
Human visitors have to be careful during the breeding season to avoid disturbances, which can be difficult due to the good camouflage of the females.