How to Identify a Greater Scaup (Aythya marila)

• Head pattern: Male and Female: head may appear more rounded in both sexes compared to Lesser Scaup; highest point toward the front of the head
• Head pattern: Male: striking black head which may show green (not purple) iridescence in good light
• Wing patch (speculum): Male and Female: bold white wing stripe extends into the primary flight feathers, the most reliable in-flight difference from Lesser Scaup
• Bill: Male and Female: rounder, larger head and a wider pale-blue bill with a notably larger black nail than Lesser Scaup
• Body pattern: Male: sides may look whiter than on Lesser Scaup

Greater Scaup shows a rounder, larger head, a wider bill, and a white wing stripe that extends into the primary feathers in flight, while Lesser Scaup has a peaked crown and its white wing stripe does not extend into the primaries The Lesser Scaup page lists its own marks.

Lakes, rivers, salt bays, and estuaries in summer; coastal bays, lagoons, and estuaries, with some on interior lakes, in winter Breeds in Alaska, northern Canada, and the far north; winters on both the Pacific and Atlantic coasts

In winter, prefers more open bays and more exposed situations than Lesser Scaup

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.