Greater Scaup

The Greater Scaup is a robust diving duck of large lakes, bays, and coastal waters, closely related to and often confused with the smaller Lesser Scaup. The breeding drake has a rounded head with a glossy dark green sheen, a black breast, a pale gray back finely marked with vermiculations, and white flanks.

Females are brown overall with a bold white patch at the base of the bill, a feature shared with the Lesser Scaup. Separating the two scaup species in the field requires close attention to head shape, wing pattern in flight, and subtle color tones.

Key Field Marks

• Rounded head shape without a peak, broadest at the rear of the crown
• Breeding drake: glossy greenish-black head sheen, black breast, pale gray back, white flanks
• Female: brown overall with a bold white patch at the base of the bill
• In flight, white wing stripe extends well out into the primary feathers (versus a shorter stripe on Lesser Scaup)

Similar Species

The Lesser Scaup is very similar but slightly smaller, with a more peaked crown (highest toward the rear-center of the head) and a purplish (rather than greenish) head sheen on the drake; its white wing stripe in flight is also shorter, mostly confined to the secondaries. Ring-necked Ducks have a more angular, peaked head and a bill with a bold white ring, and lack the scaup's white face patch on females.

Greater Scaup breed on Arctic and subarctic tundra across northern Alaska, Canada, and parts of Eurasia, nesting near tundra ponds and lakes. They winter primarily on large, open coastal waters — bays, estuaries, and the Great Lakes — more so than the Lesser Scaup, which favors a broader range of inland and coastal waters.

The species undertakes long migrations between remote Arctic breeding grounds and temperate coastal wintering areas, often forming large rafts of thousands of birds on productive wintering bays.

Greater Scaup are diving ducks, feeding primarily on mollusks and other aquatic invertebrates obtained by diving, particularly in coastal waters where they exploit mussel beds and similar prey. They also eat some aquatic plant material.

The voice is generally quiet away from the breeding grounds; males give soft, discordant courtship notes, while females give a harsher growling call. Nests are built on the ground near water on Arctic tundra, typically in a simple scrape lined with down, with females incubating 6-9 eggs alone.