Similar in appearance to scaups, but more often found in fresh marshes and wooded ponds. In flight, the dark wings are different from the white-edged wings of scaup.
Faint brown ring on drake's neck never shows in the field; light bands at tip and base of bill are conspicuous. Fly as small flocks in open formation; often land without circling. Drakes purr; hens are usually silent.
