Lesser Scaup

Aythya affinis

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Photo of a lesser scaup pair floating on water.
Lesser scaup are common migrants in Missouri and are more common than the closely related, similar-looking greater scaup.
Jim Rathert
Family

Anatidae (ducks, geese, swans) in the order Anseriformes

Description

In lesser scaup, the adult male’s head is angular or peaked, not rounded as in the greater scaup, and it has a purple (not green) sheen. Note also the smaller bill with a small nail at the tip. The white wing stripe is restricted to the secondary wing feathers; the wing stripe on the primaries is gray. The female is brown, with white around the base of the bill giving it a white "face," similar to the greater scaup female. Scaups are mostly silent. The female makes a hoarse can-can-can or a barking garf, garf, garf that is higher and softer than the female greater scaup’s. The male has a high-pitched whistle.

Similar species: The closely related greater scaup is a rare migrant in Missouri. See the paragraph above for how to distinguish between the two. Ring-necked ducks have a point or bump on the back of the head; the male has a black back, and the female a white eye-ring.

Size

Length: 17 inches (tip of bill to tip of tail).

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Photo of a male lesser scaup floating on water.
Lesser Scaup (Male)
The male lesser scaup can be distinguished from the similar greater scaup by its angular (not rounded) head with a purplish sheen.

lesser_scaup_female_2-23-15.jpg

Photo of a female lesser scaup floating on water.
Lesser Scaup (Female)
The female lesser scaup is brown, with white around the base of the bill, giving it a "white face," similar to the greater scaup female.

lesser_scaup_pair_on_lake_2-23-15.jpg

Photo of a pair of lesser scaup floating on a lake.
Lesser Scaup Pair
This photo clearly shows the angular head shape that distinguishes lesser scaup from greater scaup.

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Photo of five lesser scaups flying at Eagle Bluffs Conservation Area.
Lesser Scaup in Flight
To quickly identify if the scaups flying past you are lesser or greater scaups, look at the white patch on the upper surface of their extended wings.
Habitat and conservation

Occurs in lakes, ponds, rivers, or reservoirs, in areas free from emergent aquatic vegetation and ice. Like other bay ducks (diving ducks, or pochards), scaups can dive completely underwater. Compared to dabbling ducks, their wings are smaller relative to their body weight. To take flight, they flap their wings and run along the surface of the water, patting their feet on the surface, gaining speed and lift until they are airborne.

Foods

Like other diving ducks, scaups forage for aquatic invertebrates such as snails, crayfish, and aquatic insects, and submerged aquatic vegetation by diving completely below the surface and swimming underwater. The word scaup (pronounced “skopp”) may be related to the word scalp, akin to terms in northern European languages that mean “shell” or “shellfish bed”: In some regions, scaups feed on clams, oysters, and mussels.

image of Lesser Scaup distribution map
Distribution in Missouri

Statewide.

Status

Common migrant. Occasionally observed statewide in summer although not known to breed within our border. Lesser scaup numbers are robust but have declined nearly 60 percent between 1966 and 2015, and no one is sure why. Numerous explanations have been proposed. Habitat loss and pollution may be part of the problem, but it could also be due to the lesser scaup’s relatively late breeding time: Climate change may be causing their foods to diminish at the place and time their growing young need top nutrition.

Life cycle

Lesser scaup breed in inland Alaska, most of western Canada, and south into Montana and Wyoming. In fall, they and millions of other birds migrate south, mostly along the famous Central and Mississippi flyways, to winter in the southern United States and into Central America. In Missouri, we usually only see them in spring and fall as they migrate.

Human connections

Like other popular migratory gamebirds, their numbers are carefully monitored by state, federal, and international conservation agencies. Overhunting in the past was one reason why game laws, wildlife reserves, and conservation departments were created.

Ecosystem connections

Scaups and several other duck species have been shifting their migration routes somewhat, so that more are passing through Lake Erie, where the invasive zebra and quagga mussels have taken hold. Apparently, the large numbers of mussels offer a reliable, abundant food source for the ducks. But researchers worry that ducks feasting on these mussels may be harmed in the long run, because the filter-feeding mussels collect and concentrate pollutants in their tissues. A diet heavy with mussels contaminated with cadmium, selenium, polychlorinated biphenyls (PCBs), and other pollutants may be impairing the ducks' ability to reproduce.