Plump diving duck, typically seen in flocks in coastal areas. Males are completely black with bright orange knob on the bill. Females are brown overall with pale cheek and contrasting dark cap. Note potbellied shape and rounded head in flight. Typically coastal, but migrates over land especially in the Northeast U.S. Often gathers in tight flocks. Dives frequently, feeding on aquatic invertebrates. Breeds on ponds in Arctic tundra.