Greater Scaup Identification Guide

Key Field Marks

• Size & shape: A medium-large diving duck (bay duck) with a rounded head profile, broad body, and relatively short neck; appears bulkier and more front-heavy than Lesser Scaup.
• Male plumage: Glossy dark head with a green sheen (in good light), black breast, pale gray back finely vermiculated with black-and-white, and clean white flanks; black tail end.
• Female plumage: Rich brown overall with a bold, sharply defined white patch at the base of the bill — larger and more clean-edged than on female Lesser Scaup.
• Bill: Broad, blue-gray ("blue bill") with a black nail at the tip; noticeably broader than Lesser Scaup's bill, with the black nail comparatively small.
• In flight: Shows a white wing stripe that extends well out into the primaries (unlike Lesser Scaup, where it is mostly limited to the secondaries) — the single most reliable mark for separating the two species in flight.
• Behavior: Dives frequently to feed on mollusks and aquatic invertebrates; forms large rafts, often in open water well offshore, more so than Lesser Scaup.

Separating It From Similar Species

• Lesser Scaup is the classic confusion species: Lesser has a more peaked head shape (with a slight bump toward the rear crown), a purple (not green) gloss on the male's head in good light, a narrower bill with a larger black nail, and a shorter white wing stripe confined mostly to the secondaries. Head shape is the most useful mark on swimming birds; the wing stripe is definitive in flight.
• Ring-necked Duck shows a peaked head, a white ring near the bill tip and a pale band on the bill, and a black back (vs. pale gray on scaup) — readily separable with a good look.
• Female scaup can suggest female Ring-necked Duck, but Ring-necked lacks the sharply set-off round white face patch and shows the peaked head and pale-ringed bill instead.

Where & When to See It

• Habitat: Large lakes, reservoirs, coastal bays, and estuaries; more tied to big, open, often brackish or salt water than Lesser Scaup, especially in winter.
• Range: Breeds across the far north (Alaska, northern Canada, Arctic tundra and taiga); winters along both U.S. coasts, the Great Lakes, and larger inland lakes across temperate North America, as well as parts of Europe and Asia (Holarctic distribution).
• Season: A winter visitor through most of its U.S./southern Canada range, present roughly October–April, with breeding confined to the Arctic and subarctic in summer.

Voice

• Generally quiet away from breeding grounds. Males give soft, discordant whistling notes during courtship; females give a harsher, growling arrr or garf call, mainly on breeding territory.