58-69 cm (23-27") Locally abundant. Sea duck. Often seen in large flocks along coastal waters; casual on Great Lakes. Largest North American duck. Distinctive long sloping forehead accentuated by long slender frontal bill-shield.
Male: white head with black cap; greenish hindneck; white throat, neck, breast and back; black sides and tail.
Female: color ranges from overall rich brownish-red to gray; heavily barred sides.
In flight: flies in long lines close to water surface; males show white back; black tail.
Song: moaning sounds, hoarse quacks.