A bulky seaduck with a total body length of 44 to 54 cm. The tail is long and pointed and the bill fairly small. In the male, the entire body plumage, tail and legs are black (the only totally black duck) with a yellow-orange patch on an otherwise black bill. Females are uniformly dark brown with the exception of the side of the head and nape which is a pale dusky brown, with a blackish bill. In late summer, females may display pale, bleached feathers on the back. Juveniles resemble adult females but with a paler light brown belly.