Other Names: none
Distribution: Alaska and northern Canada in summer; North American coasts in winter.
Size: 32-38 cm in length with a 53-56 cm wingspan.
Plumage: Males are largely white, with a black back, a black head with a greenish and/or purplish gloss, and a large white patch from behind the eye to the top and back of the head. Females are all dark, with a single whitish patch on the cheek. The bill and eyes are black.