Lesser Scaup (Aythya affinis)



Lesser Scaup

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The lesser scaup is a small diving duck commonly found in North America. It is most commonly found in the northern and central United States and southern Canada.

The lesser scaup is sometimes known by a few different colloquial names, including “little bluebill.”

As diving ducks, they are well-adapted for foraging in the water, and they use their strong legs and webbed feet to swim and dive in search of food. They are active when diving and surfacing repeatedly.

Scientific Name: Aythya affinis

Height: 41.7–43 cm (16.4–16.9 in)

Wingspan: 68–78 cm (27–31 in)

Weight: 454–1,089 g (1.001–2.401 lb)

Physical Characteristics of the Lesser Scaup

The lesser scaup is closely related to the greater scaup and looks similar to the ring-necked ducks.

The adult male lesser scaup is a medium-sized diving duck with a tall, peaked head and distinctive black and white plumage. Its head is glossy black, with a purple to green sheen that is only visible in good lighting conditions.

The back of its head and neck is flat, with a pale blue bill and a narrow black nail. Its back is gray, and its sides are white, giving it a striking two-tone appearance. It has a yellow eye and a black breast.

The adult female lesser scaup is similar in appearance to the male but has few key differences.

Unlike the male, who has a glossy black head and white sides, the adult female has a dark brown plumage that shades white on the mid-belly. Additionally, the female has a white band or white patch at the base of its bill, and its ear region is often lighter in color than the rest of its body.

The females have a smaller size than the males.

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Breeding Range of the Lesser Scaup

The lesser scaup breed in many habitats throughout much of North America.

In the United States, it is commonly found in the northern and central parts of the country, including states such as Montana, North Dakota, South Dakota, and Wyoming. Additionally, breeding populations occur in a few isolated west coast regions, including the Great Lakes and Klamath region of southern Oregon and northeastern California.

The population range of the lesser scaup extends from the northern United States to the Bering Sea and includes the Prairie Pothole Region.

In Canada, it breeds along British Columbia, Alberta, Manitoba and Ontario coasts. While they are less common further east into Quebec and Nova Scotia, there have also been reports of breeding pairs in these locations.

Migration & Habitat

During the fall and winter, these birds migrate to their wintering grounds in search of more favorable conditions. Like many other species of waterfowl, they typically follow specific flyways, or pathways, that their ancestors have used for generations.

The exact flyways used by these waterfowl may vary depending on where they breed and where they winter. Generally, they are known to migrate along North America’s Atlantic, Central and Mississippi flyways.

These flyways extend from the northern United States and Canada, down through the central and eastern parts of the continent, and into the southern United States, Mexico and other parts of Central America.

Along these flyways, the majority of lesser scaups can access a wide range of wintering habitats, including coastal bays, reservoirs, estuaries, marshes, lakes, ponds and rivers, where they can find food and shelter during the colder months.

Diet & Feeding Habits

The lesser scaup primarily feeds by diving and swimming underwater, using its wings to propel itself. The bird dives down to depths of up to six feet and searches for food on the lake or sea floor.

Its diet consists mainly of aquatic invertebrates such as aquatic insects, mollusks, crabs, shrimps, and crayfish.

In addition to foraging for food underwater, the lesser scaup will also scavenge for food on the shoreline. However, this is usually done in shallow waters near the coastline where it can search for food items like small fish or worms left behind by other animals or washed up onto the shore.

During the breeding season, lesser scaups may also feed on animal matter, such as surface insects, while flying over lakes and marshes.

In terms of diet, the lesser scaup is known to eat a variety of plant materials such as aquatic plants, algae and submerged vegetation. It is also known to eat roots, seeds and stems, such as wild celery, cattails and bulrushes.

The varied diet of the lesser scaup depends on the season and food availability.

Mating Habits

Lesser scaup pairs are relatively solitary and only come together to mate. The couple typically forms during the late spring migration, and the birds are monogamous, although mate-switching is common.

During courtship, the male lesser scaup performs a variety of displays to attract a mate. These displays include head-shaking, bowing movements, and ritualized preening; some are even performed underwater.

One of the most distinctive displays is the “head throw,” in which the male throws his head far back and then brings it forwards very quickly. This display is thought to serve as a visual cue to the female, and other ritualized movements and vocalizations often accompany it.


During the breeding season and in the summer, the female lesser scaup builds a nest on the ground, usually near the water’s edge, and lays a clutch of 8-14 olive-buff eggs. She incubates the eggs herself, and the incubation period lasts 21-27 days.

Their breeding grounds are usually dry land close to the water, with dense vegetation. Their nests are made from dry grass and other soft plant materials.

Once the eggs hatch, the young ducklings leave the nest shortly afterward and go to the water, where the female tends them. However, the young can feed themselves and forage for food on their own from an early age.

In some cases, multiple broods of young may join together and be cared for by several adult females. The young birds reach maturity at around 47-54 days after hatching. At this point, they can fly and become independent.

Population & Conservation Status

The global breeding population of the species is estimated to be 3.7 million individuals, with a stable population trend. This species is listed as Least Concern by the International Union for Conservation of Nature (IUCN).

Unfortunately, it is difficult to distinguish the actual population trend of the two species of scaups since they are often found in dense flocks and large numbers in the hundreds, sometimes even thousands.

This species faces threats from habitat loss due to climate change, agricultural development, pollution from runoff into their natural breeding habitat, oil spills and hunting pressure during migration and winter months.

However, its large range and global population mean that it should remain stable for the foreseeable future, provided that conservation efforts are taken to protect its wetland habitats from damage or destruction.


The US Fish and Wildlife Service (USFWS) allows the hunting of lesser scaup in many parts of the country during designated season periods. However, hunters must check specific state regulations before any activity.

Key Points

  • Like other ducks, these birds migrate south in the winter to find better food sources.
  • The lesser scaup looks similar to the greater scaup and the ring-necked duck.
  • These ducks breed in Alaska and western Canada.

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