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lesser scaup

Aythya affinis

What do they look like?

Lesser scaup are medium-sized diving ducks. Males are slightly larger than females. Males and females have different feather colors throughout most of the year. Males in breeding plumage (August to the following June) have a blue bill and purplish-black head, breast, neck, tail, and vent. The sides and belly are white and the back is white with grey spots. Females are chocolate brown, with lighter sides, a reddish head, and a white patch at the base of their dark grey bill. In all lesser scaup there is a white wing stripe on the trailing edge of the upper wing surface.

  • Sexual Dimorphism
  • male larger
  • sexes colored or patterned differently
  • male more colorful
  • Range mass
    600 to 1200 g
    21.15 to 42.29 oz
  • Range length
    39.1 to 45.1 cm
    15.39 to 17.76 in

Where do they live?

Lesser scaup are an American species of diving duck. They breed in cold, northern lakes in interior Alaska and Canada and into parts of the northern United States. In winter they are found on bodies of water along the Pacific and Atlantic coasts of the United States, the southern United States, Florida, and along the Atlantic coast to Massachusetts. They are also found in the southern Great Lakes region and Ohio and Mississippi river drainages. Lesser scaup also winter throughout Mexico and Central America, the Antilles, and the Hawaiian Islands.

What kind of habitat do they need?

Lesser scaup breed and look for food in wetland habitats. They are found throughout the year on wetlands, lakes, ponds, and along coastlines with vegetation in and above the water, like cattails or bulrushes and pondweed or water milfoil,. Lesser scaup are most common on ponds with lots of amphipods for them to eat. They build their nests on the land near ponds.

How do they reproduce?

Lesser scaup form male-female pairs for the breeding season when they are migrating in the spring. Before the females begin laying eggs, they sometimes switch mates.

Lesser scaup nest later than most other North American ducks. They arrive in the breeding area in May and build nests and lay eggs in June. Females and males start the nest as a shallow depression in a grassy area, gradually adding grasses and feathers to form a bowl throughout incubation. Females lay from 6 to 14 pale, greenish eggs in a clutch. They lay 1 egg per day until the clutch is complete and begin incubating a day or two before the final egg is laid. Some females lay eggs in the nests of other females. Males abandon their female mates about mid-way through incubation, which lasts 21 to 27 days. Young can fly 47 to 61 days after hatching. Males and females can breed in the first year after hatching.

  • How often does reproduction occur?
    Lesser scaup breed once yearly, they typically lay one clutch, but may attempt a replacement clutch if the first is destroyed early in the season.
  • Breeding season
    Breeding occurs in May and June.
  • Range eggs per season
    6 to 14
  • Average eggs per season
  • Range time to hatching
    21 to 27 days
  • Range fledging age
    47 to 61 days
  • Range time to independence
    2 to 5 weeks
  • Average age at sexual or reproductive maturity (female)
    1 years
  • Average age at sexual or reproductive maturity (male)
    1 years

Only females incubate the eggs and care for the young after hatching. Males abandon females when they are incubating the eggs. Young are able to walk and feed themselves when they hatch. Females lead the young away from the nest within a day of hatching. Young feed from the water surface at first, but feed by diving by 2 weeks old. Females stay with the young for 2 to 5 weeks after hatching, but then abandon them, often before they begin to fly.

  • Parental Investment
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • protecting
      • female

How long do they live?

Most lesser scaup die within the first few weeks of hatching from predation and being exposed to cold weather. The maximum lifespan in the wild is 18 years, 4 months. Between 32 and 71% of lesser scaup die each year, depending on the area.

  • Range lifespan
    Status: wild
    18.33 (high) years

How do they behave?

Lesser scaup are non-aggressive birds that are found in large flocks throughout most of the year, except for the breeding season. In winter they form large flocks for molting and migration. Flocks as large as 500,000 have been reported. They are active during the day, feeding for about 20 minutes at a time throughout the day.

Home Range

Lesser scaup do not defend territories. When they breed, pairs have small home ranges that overlap with those of other scaup. Females return each year to the area where they hatched.

How do they communicate with each other?

Lesser scaup use a set of visual displays, sometimes with calls, during courtship. The most common display is called the "cough" because they give a short "whew" sound while they flick their wings and tail. Males also use a head-throw and kinked-neck display to attract females. Females also make a soft "arrr" sound during courtship.

What do they eat?

Lesser scaup adults and young eat insects, crustaceans, and mollusks. Amphipods, midges, and leeches are especially important in the diet. They sometimes also take the seeds of aquatic plants. They forage in shallow, open water by diving. They mostly eat prey underwater, but will bring larger prey to the surface.

  • Animal Foods
  • fish
  • eggs
  • insects
  • mollusks
  • terrestrial worms
  • aquatic crustaceans
  • Plant Foods
  • seeds, grains, and nuts

What eats them and how do they avoid being eaten?

Ducklings that are attacked by predators try to stay together and females will try to protect their young. Females try to keep their young near the cover of plants and the dull brown feathers of ducklings may help to protect them. Adults may pretend to be dead when attacked by large predators. Most predation is on eggs and hatchlings. Eggs are taken by American mink, raccoons, red foxes, American crows, ring-billed gulls, California gulls, common ravens, and American badgers. Ducklings are taken by many of the same predators, as well as black-billed magpies, great horned owls, black-crowned night herons, Swainson's hawks, American coots, and Arctic loons. Adults are taken by the other mammal predators mentioned and striped skunks and coyotes when they are on the nest. Adults are also taken by snapping turtles, red-tailed hawks, peregrine falcons, snowy owls and bald eagles.

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Lesser scaup are important predators of aquatic invertebrates in northern lakes. Eggs and hatchlings are taken by a wide range of predators. They fall ill with a range of diseases and parasites, including avian influenza, avian cholera, avian botulism, aspergillosis, and a variety of worms and blood parasites.

Lesser scaup nests are parasitized by other lesser scaup as well as by other ducks, including redheads, gadwall, white-winged scoters, ruddy ducks, canvasbacks, and red-breasted mergansers. Lesser scaup also parasitize the nests of other ducks, including gadwall, orthern shovelers, redheads, white-winged scoters, and canvasbacks. (Austin, et al., 1998)

Commensal or parasitic species (or larger taxonomic groups) that use this species as a host

Do they cause problems?

There are no known adverse effects of lesser scaup on humans.

How do they interact with us?

Lesser scaup are important members of North American wetland ecosystems. They are also hunted during migration. (Austin, et al., 1998)

  • Ways that people benefit from these animals:
  • food
  • body parts are source of valuable material

Are they endangered?

Lesser scaup are not considered threatened because they have large population sizes and a large range. They are one of the most abundant duck species in North America. However, in some areas people have noticed population declines that may be the result of losing wetland habitats, pollution, and lack of sufficient prey.

Some more information...

Lesser scaup are most closely related to greater scaup (Aythya marila), which are a primarily coastal, maritime species. (Austin, et al., 1998)


Tanya Dewey (author), Animal Diversity Web.


Anteau, M., A. Afton. 2004. Nutrient reserves of lesser scaup (Aythya affinis) during spring migration in the Mississippi flyway: a test of the spring condition hypothesis. The Auk, 121: 917-929.

Austin, J., C. Custer, A. Afton. 1998. Lesser Scaup (Aythya affinis). The Birds of North America Online, 338: 1-17.

BirdLife International 2008, 2008. "Aythya affinis" (On-line). The IUCN Redlist. Accessed April 02, 2009 at

Custer, C., T. Custer, M. Anteau, A. Afton, D. Wooten. 2003. Trace Elements in Lesser Scaup (Aythya affinis) from the Mississippi Flyway. Ecotoxicology, 12: 47-54.

Dawson, R., R. Clark. 1996. Effects of variation in egg size and hatching date on survival of Lesser Scaup Aythya affinis ducklings.. Ibis, 138: 693-699.

Lindeman, D., R. Clark. 1999. Amphipods, land-use impacts, and lesser scaup (Aythya Affinis) distribution in Saskatchewan wetlands. Wetlands, 19: 627-638.

University of Michigan Museum of ZoologyNational Science Foundation

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Dewey, T. 2009. "Aythya affinis" (On-line), Animal Diversity Web. Accessed April 21, 2024 at

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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