Greater scaup Greater scaup The greater scaup ("Aythya marila"), just scaup in Europe or, colloquially, "bluebill" in North America, is a mid-sized diving duck, larger than the closely related lesser scaup. It spends the summer months breeding in Alaska, northern Canada, Siberia, and the northernmost reaches of Europe. During the winter, it migrates south to the coasts of North America, Europe, and Japan. Drake greater scaup are larger and have more rounded heads than the females; they have a bright blue bill and yellow eyes. Their heads are dark, with a green gloss; the breast is black, the belly white and the
Lesser scaup where the white extends to the eye region. But especially with juveniles, the bi-colored bill of hybrids is most diagnostic. Hybrid combinations that are known from the wild and resemble the lesser scaup are: In theory, each and every "Aythya" species is able to produce potentially fertile hybrids with any other, though due to their different ranges and behavioral cues given during courtship most of these hybrids are only known from birds kept in captivity without conspecific mates. Their breeding habitat is inland lakes and marsh ponds in tundra from Alaska through western Canada to western Montana; few breed east