Except for the wing marks, greater and lesser scaup appear nearly identical in the field. The light band near the trailing edges of the wings runs almost to the tip in the greater scaup, but only about half way in the lesser.
Greater scaup prefer large open water areas; lesser scaup often use marshes and ponds. Both species migrate late, sometimes just before freezeup. Flock movements are rapid, often erratic, usually in compact groups. Hens are silent; drake lesser scaup purr; drake greater scaup have a discordant scaup, scaup.