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 of James Bay and the Great Lakes. Notable breeding concentrations, with more than half a million birds at the height of the season, can be found in Alaska, in the woodlands of the McKenzie River valley and on the Old Crow Flats. These birds migrate south (mostly via the Central and Mississippi Flyways) when the young are fledged and return in early spring, usually arriving on the breeding ground in May. Lesser scaup typically travel in flocks of 25–50 birds and winter mainly on lakes, rivers and sheltered coastal lagoons and bays between the US–Canada border and northern Colombia, including