Guide to North American Birds

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Breeding adult male. Photo: Brian Kushner

Lesser Scaup

Aythya affinis

One of the most numerous and widespread diving ducks in North America, especially on inland waters. Can be very active when feeding, diving and surfacing repeatedly. In winter often seen on lakes and bays in dense flocks, numbering hundreds or even thousands, and often with no other species of ducks associated with them. The two species of scaup sometimes occur in the same places, but they tend to keep to themselves rather than mixing freely.

Conservation status	Although it is still abundant, the total population has declined significantly in recent decades, and the causes are not well understood.
Family	Ducks and Geese
Habitat	Marsh ponds (summer), lakes, bays, estuaries. Summers around large marshes in prairie or forested regions. Winters on lakes, reservoirs, rivers, sheltered areas of coastal bays. Overlaps extensively with Greater Scaup, especially in winter, but at that season the Lesser is far more likely to be found on freshwater lakes and ponds well inland.

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Feeding Behavior

Forages by diving and swimming underwater; sometimes by dabbling or up-ending in shallow water. Sometimes feeds at night.

Eggs

9-11, sometimes 8-14. Olive-buff. Incubation is by female only, 21-27 days. Young: Leave nest shortly after hatching, go to water. Young are tended by female but feed themselves. 2 or more broods of young may join under care of several adult females. Age at first flight 47-54 days after hatching.

Young

Leave nest shortly after hatching, go to water. Young are tended by female but feed themselves. 2 or more broods of young may join under care of several adult females. Age at first flight 47-54 days after hatching.

Diet

Includes mollusks, plant material. Diet varies with season and habitat, but animal matter may predominate, especially mollusks such as clams and snails, also aquatic insects, crustaceans. Also eats plant material such as stems and leaves of sea lettuce, pondweeds, wild celery, plus seeds of pondweeds, sedges, grasses, and others. Birds on the Great Lakes may feed heavily on the introduced zebra mussel.

Nesting

Probably first breeds at age of 2 years in most cases. Elements of courtship display by male include a shake of the head, followed by throwing the head far back and bringing it forward very quickly; exaggerated bowing movements; ritualized preening. Some displays may be performed underwater. Nest site is usually on dry land close to water, often on islands in lakes, surrounded by good cover of vegetation. Stands of bulrush in marshes especially favored. Nest is a slight depression with addition of some dry grass, lined with down.

Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds

Migration

Migrates in flocks. Main migration is rather late in fall and early in spring.

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Migration

Migrates in flocks. Main migration is rather late in fall and early in spring.

All Seasons - Common
All Seasons - Uncommon
Breeding - Common
Breeding - Uncommon
Winter - Common
Winter - Uncommon
Migration - Common
Migration - Uncommon

Songs and Calls

Seldom heard; sharp whistles and guttural scolding notes.

Audio © Lang Elliott, Bob McGuire, Kevin Colver, Martyn Stewart and others.
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How Climate Change Will Reshape the Range of the Lesser Scaup

Audubon’s scientists have used 140 million bird observations and sophisticated climate models to project how climate change will affect this bird’s range in the future.

Zoom in to see how this species’s current range will shift, expand, and contract under increased global temperatures.

Climate threats facing the Lesser Scaup

Choose a temperature scenario below to see which threats will affect this species as warming increases. The same climate change-driven threats that put birds at risk will affect other wildlife and people, too.