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
Greater scaup 100% of female greater scaup, and 77% of female lesser scaup, had escalated levels of selenium in their bodies. Selenium is an occurring semimetallic trace element that occurs naturally in some soils and minute amounts are necessary for animal life. However excessive selenium can cause reproductive harm and is highly toxic. On their migration across the Great Lakes, greater scaups are at risk of ingesting selenium by eating the invasive zebra mussels, which can render a hen infertile. This sterilization of hens is causing the population to decrease. In a study of 107 scaup, they all had traces of iron,