The Adult Greater Scaup Ducks have blue bill and yellow eyes and is 20% heavier and 10% longer than the closely related Lesser Scaup. The male has a dark head with a green sheen, a black breast, a light back, a black tail, and a white underside. The drake or male Greater Scaup is larger and has a more rounded head than the female. The drake's belly and flanks are a bright white. Its neck, upper chest, and tail feathers are a glossy black, while its lower flanks are gray. The drake also has a white speculum on its wings. The adult female has a white band and brown oval shaped patches at the base of the bill, which is a slightly duller shade of blue than the drake's bill. Females have grey on both their legs and feet. They have a brown body and head, with white bands on their wingtips. Juvenile Greater Scaup look similar to adult females. The Greater Scaup drake's eclipse plumage looks similar to its breeding plumage, except the pale parts of the plumage are a buffy gray. Distinguishing Greater from Lesser scaups can be extraordinarily difficult in the field, especially in terms of plumage, although (depending on posture) their general shape is slightly different.