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HomeSpits­ber­gen infor­ma­ti­onWild­life → Com­mon eider duck

Common eider duck (Somateria mollissima)

The com­mon eider duck is usual­ly easi­ly reco­gni­zed by its size, the black bel­ly and the white back of the male. Pre­vious­ly, the excel­lent insu­la­ting down were collec­ted from the nests of eider ducks for clot­hing or blan­kets.

Common eider ducks, Forlandsund

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.

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last modification: 2017-11-15 · copyright: Rolf Stange
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