Greater scaup been described by Serebrovskij in 1941 from fossils recovered at Binagady, Azerbaijan. The greater scaup's name may come from "scalp", a Scottish and Northern English word for a shellfish bed, or from the duck's mating call: "scaup scaup". A phylogenetic analysis of the diving ducks, examining the skeletal anatomy and skin, found that the greater and lesser scaups are each other's closest relatives, with the tufted duck as the next closest relative of the pair. The adult greater scaup is long with a wingspan and a body mass of . It has a blue bill and yellow eyes and is
Lesser scaup Chasewater, Staffordshire in 1987 but by 2006, over 60 had been recorded, with an average of 2 per year. UK records are typically in the northern parts of the country. Vagrant lesser scaup have also been recorded on the Hawaiian Islands Japan, possibly China, and—for the first time on 18 January 2000—in the Marianas, as well as in Ecuador, Surinam, Trinidad and Venezuela (in winter), and Greenland (in summer). Lesser scaup forage mainly by sifting through the bottom mud, usually after diving and swimming underwater, occasionally by dabbling without diving. They mainly eat mollusks such as mussels and clams, as