The Greater Scaup (Aythya marila) is a powerfully built diving duck, 40–51 cm long with a wingspan of 71–84 cm and a weight of 700–1,400 g. The drake in breeding plumage has a black, green-glossed head, black breast and rear end, and white flanks; the key mark separating it from the very similar Tufted Duck is the pale, grey-vermiculated back — the Tufted Duck's back is solid black — and the Greater Scaup also lacks the Tufted Duck's drooping head tuft. The female is brown with a broad, well-defined white patch around the base of the bill, and both sexes show a white wing bar in flight.
Mostly silent outside the breeding season, displaying males give a soft cooing while females produce a harsh, rasping quack. The species breeds sparsely in Swedish mountain tarns and mires in the north, with a small population of a few thousand pairs, but its real importance in Sweden lies in winter, when northern populations gather in the Baltic and in strait areas; large rafts can be seen in shallow coastal bays, including Öresund, from November to March. As a short-distance migrant it moves no further than necessary to find ice-free water. A skilled diver, it feeds mainly on mussels, snails and crustaceans taken from the bottom, supplemented by aquatic insects and plant matter, with the blue mussel an important food source on its Baltic wintering grounds. Though still globally Least Concern, the species has declined markedly in Europe, especially in the Baltic — one of its key wintering areas — and is classed as Near Threatened (NT) in Sweden.
Read about this species in Swedish →