Greater Scaup

Overview

The Greater Scaup is a stocky diving duck in the genus Aythya, closely related to the Lesser Scaup but generally larger, bulkier, and tied more to coastal and marine waters. Breeding males show a rounded, glossy dark head, pale gray back, and crisp white flanks, while females are brown with a bold white patch at the base of the bill. Scaup gather in large rafts on open water outside the breeding season, diving to feed along the bottom.

Because it looks so similar to the Lesser Scaup, feather and plumage details such as head shape, gloss color, and the extent of white in the wing are the most reliable ways to separate the two in hand or in flight.

Feather Identification

• Wing stripe: The white speculum (secondary panel) extends well into the primary feathers, appearing as a long white stripe along much of the open wing in flight - a key difference from Lesser Scaup, where the white is largely confined to the secondaries.
• Head feathers: Male head feathering has a greenish sheen (versus purplish in Lesser Scaup) under good light, though this can be subtle and lighting-dependent.
• Back and flank feathers: Fine, pale gray vermiculations on the back contrast with clean white flank feathers in breeding males.
• Body shape cues: Rounded head profile (highest point over the center of the crown) versus the more peaked rear-crown shape typical of Lesser Scaup.
• Female facial feathers: A bold, well-defined white patch surrounds the base of the bill, often slightly larger and more sharply bordered than in Lesser Scaup.

Plumage Notes

Adult males in breeding (alternate) plumage show a black, glossy head, black breast, pale vermiculated gray back, and white flanks with a dark rear end. Females are warm brown throughout with the diagnostic white face patch, which can shrink or become less crisp later in the season. After breeding, males molt into a duller eclipse plumage resembling females but retaining some gray back feathering and a darker overall head. Wing molt is simultaneous, leaving the birds flightless for a few weeks in late summer, a pattern shared with other diving ducks. First-year birds resemble adult females and gradually acquire full adult male patterning over their first year.

Habitat & Range

Greater Scaup breed on tundra ponds and lakes across the far north of North America and Eurasia, then migrate to winter along coastal bays, estuaries, and large lakes, often in enormous mixed flocks with other diving ducks. They favor larger, more open and often brackish or saltwater bodies than Lesser Scaup, which tend toward inland freshwater lakes and reservoirs in winter. The species is migratory, with populations shifting from arctic breeding grounds to temperate coastlines each fall.

Behavior & Field Notes

Greater Scaup are active divers, disappearing underwater for extended periods to forage on mollusks and aquatic invertebrates along the bottom. They are highly gregarious outside the breeding season, forming dense rafts numbering in the thousands on favored bays. Flight is fast and direct, typically low over the water in tight flocks. Nesting occurs on the ground near water in the arctic, with females taking on all incubation and brood-rearing duties. Vocalizations are generally soft and infrequent compared to dabbling ducks, with males giving a soft whistling note during courtship and females a harsher growl.