Size: L: 40cm (male tail length 15cm). Wt: Males: 800 g. Females: 650 g. Sexually and seasonally dimorphic. Birds only seen on Great Lakes in winter plumage.
Winter Male: forehead, crown, and nape white; face buff; large brown head patch; white eye ring; bill dark, with pink band; breast blackish; back and flanks white; tail black, central feathers narrow, elongate.
Winter Female: head white, with grayish patches on crown and cheek; bill grey; faint mottled neck band; breast, belly, and flanks white; back mottled grey-brown; tail dark, with no elongate feathers.
Juvenile: young males similar to females, but head markings larger and darker, back dark brown, bill with pink V