How to Identify a Lesser Scaup (Aythya affinis)

• Head pattern: Male and Female: peak at the back of the crown, the best mark for separating this species from Greater Scaup
• Head pattern: Male: often shows purple gloss on the head in good light, versus green gloss typical of Greater Scaup
• Body pattern: Male: black at both ends (head/chest and stern) with a whitish middle body, shared pattern with Greater Scaup
• Head pattern: Female: brown head with a white patch at the base of the bill, no white ring on the bill itself
• Wing patch (speculum): Male and Female: shorter white wing stripe than Greater Scaup, reaching only about halfway out the wing and not extending into the primaries

Head shape is the best mark: Lesser Scaup has a peak at the back of the crown and a slightly smaller bill than Greater Scaup, and shows a shorter white wing stripe in flight that reaches only about halfway out the wing The Greater Scaup page lists its own marks.

Marsh ponds in summer; lakes, bays, and estuaries; lakes, reservoirs, rivers, and sheltered coastal bays in winter Breeds across Alaska and Canada's boreal/prairie regions; winters widely across the US including the Great Lakes, Mid-Atlantic, and Gulf Coast

Shoot from water level if you can, with the sun behind you, so head pattern and the wing patch show their true colors. Get one frame with the bird side-on and one as it stretches or flaps, which exposes the speculum and belly. Note who it is swimming with; ducks flock by species. The app names the likely species; confirm with the marks above, and check the female separately, since females of many ducks look alike.