The long-tailed duck (Clangula hyemalis), once known as oldsquaw, is a medium-sized sea duck. It is the only living member of its genus, Clangula.
Adults have white underparts, though the rest of the plumage goes through a complex moulting process. The male has a long pointed tail (10 to 15 cm (3.9 to 5.9 in) long) and a dark grey bill crossed by a pink band. In winter, the male has a dark cheek patch on a mainly white head and neck, a dark breast and mostly white body. In summer, the male is dark on the head, neck and back with a white cheek patch. The female has a brown back and a relatively short pointed tail. In winter, the female’s head and neck are white with a dark crown. In summer, the head is dark.