Written by Peter Pearsall/Photo by Dan Streiffert

The lesser scaup (Aythya affinis), also known as the “little bluebill,” is a medium-sized diving duck in the family Anatidae found across North America. Males have a blue-gray bill, yellow eyes, and a black head with a purple iridescent sheen. Females are brownish, with a white patch at the base of the bill. 

Lesser scaup and greater scaup are notoriously difficult to distinguish, but the lesser scaup has a peaked rather than rounded shape to its head. Both species feed on aquatic invertebrates (e.g., snails, insects, and crustaceans) as well as seeds and plant matter during the non-breeding season, diving to the bottom of water bodies to gather food. 

The lesser scaup breeds along boreal lakes and prairie wetlands in Canada and the northern United States. It spends winters in coastal regions, inland lakes, and reservoirs across the southern United States, Mexico, and Central America. At Malheur Refuge, lesser scaup are common migrants in spring and fall, with few remaining to nest in summer.

Unlike other diving ducks, which often place their nests over water, the lesser scaup prefers drier sites with nest placement on moist meadows, dry uplands, or islands. The female lays 6–14 eggs that are incubated for 23-27 days. Ducklings are precocial, able to feed themselves shortly after hatching. 

Lesser scaup is the most abundant diving duck in North America, with a global breeding population estimated at 3.8 million.