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Species Guide
A photo of a Lesser Scaup (Aythya affinis), male
Lesser Scaup, Male

Lesser Scaup

Aythya affinis

The Lesser Scaup, a small North American diving duck, is known for its distinctive blue bill, earning it the nicknames "little bluebill" or "broadbill." This species, Aythya affinis, is closely related to the Greater Scaup and is part of a superspecies with it. Adult Lesser Scaups measure between 38–48 cm in length, with males averaging 820 g and females, slightly lighter, at 730 g. Their wingspan stretches from 68–78 cm.

Identification Tips

Males, or drakes, display a black, iridescent head with a small tuft at the hindcrown during breeding plumage, along with a black breast and whitish-grey back. Females, or hens, feature a white band at the base of the bill and are generally dark brown, fading to white on the belly. Both sexes boast white secondary remiges and a blue-grey bill with a black tip. The drake's bright yellow iris contrasts with the female's orange to yellow, and the immature's brown eyes.


Lesser Scaups favor inland lakes and marsh ponds within the tundra for breeding, from Alaska through western Canada to western Montana.


These ducks migrate southwards to as far as Central America during winter, returning to their breeding grounds in early spring. They are also known to winter on lakes in parks and occasionally appear as vagrants in western Europe.


Lesser Scaups typically travel in flocks of 25–50 birds. They forage by sifting through bottom mud, diving and swimming underwater, or occasionally dabbling. Breeding begins in May, with nesting usually in June. Males leave the incubation and rearing to the females as they moult into eclipse plumage.

Song & Calls

The females emit a discordant scaup call, while the males produce weak whistles during courtship. The female's call is more frequent than that of the Greater Scaup but is a weaker, guttural sound.


Nesting occurs near water among thick vegetation, sometimes in small groups or near gull or tern colonies. Clutches average 9–11 eggs, with incubation lasting around 3 weeks and fledging at 45–50 days.

Similar Species

The Lesser Scaup can be challenging to distinguish from the Greater Scaup, especially when direct comparison isn't possible. Key differences include bill shape and head profile, with the Lesser Scaup having a smaller, straighter bill and a less bulging forehead.

Diet and Feeding

Their diet consists mainly of mollusks, aquatic plant seeds, and in winter, aquatic animals like crustaceans, insects, and small fish. They have adapted to feed on zebra mussels in Lake Erie.

Conservation Status

Despite a steady population decline since the mid-1980s, the Lesser Scaup is classified as a Species of Least Concern by the IUCN. The reasons for the decline are not fully understood, but it is not considered to be due to hunting or habitat destruction on breeding grounds.

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Lesser Scaup Fun Facts

Did you know?
The Lesser Scaup is the most abundant diving duck in North America with a breeding population of 3.8 million.

Lesser Scaups on Birda


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