Lesser scaup are an American species of diving duck. They breed in interior boreal forests and parklands of Alaska and Canada and into the United States in North and South Dakota, Montana, Wyoming, northeastern Washington, and the Klamath region of southern Oregon and northeastern California. In winter they are found in appropriate habitat in the Pacific coastal states, the southern states, including Colorado, the southeast, 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. Occasional birds are seen in winter in the western Palearctic, Greenland, British Isles, Canary Islands, and the Netherlands.

Biogeographic Regions: nearctic (Native ); neotropical (Native )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDING: central Alaska and Mackenzie Delta to northern Manitoba and northern Ontario south to southern British Columbia, northern Idaho, northern Wyoming, northern North Dakota, and Minnesota, casually or irregularly east to central Quebec and south to Washington, central California, northern Utah, central Colorado, central Nebraska, northwestern Iowa, central Illinois, and northern Ohio (AOU 1998). NON-BREEDING: southern Alaska, and from southern British Columbia, southern Idaho, Utah, northeastern Colorado, Kansas, Iowa, southern Great Lakes region, and New England south throughout the southern U.S., Middle America, and West Indies to northern Colombia, northern Venezuela (very small number at southern limit of this range); small numbers in Hawaii. Primary wintering areas in the U.S. include the Atlantic and Gulf coastal plains, Mississippi Valley north to the Ohio River, and the Pacific states, plus southern British Columbia; the highest densities occur in southern Florida and along the Mississippi River (Root 1988).

Lesser scaup are medium-sized diving ducks. Males are slightly larger than females: from 40.4 to 45.1 cm in males and 39.1 to 43.4 cm in females, and from 700 to 1200 g in males and 600 to 1100 g in females. Males and females have different plumage patterns throughout most of the year. Males in breeding plumage (August to the following June) have a blue bill, purplish-black head, breast, neck, tail, and vent. The sides and belly are white and the back is white with grey flecking. Females are chocolate brown, with lighter sides, a rufous head, and a white patch at the base of their dark grey bill. In all birds the secondary feathers are white at the end, resulting in a white wing stripe on the trailing edge of the upper wing surface. Iris color varies with sex and age. Irises are grayish in hatchlings, become yellow-green in juvenile males, and then deep yellow in adult males. Iris color in females stays a brownish color.

Lesser scaup are difficult to distinguish from their close relatives, greater scaup (Aythya marila), especially at a distance. There is no documented geographic variation and no subspecies described.

Range mass: 600 to 1200 g.

Range length: 39.1 to 45.1 cm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger; sexes colored or patterned differently; male more colorful

Length: 42 cm

Weight: 850 grams

• Terrestrial
• Freshwater
• Marine

Lesser scaup are reliant on wetland habitats for foraging and breeding. They are found throughout the year on semi-permanent or seasonal wetlands with emergent vegetation (such as cattails, Typhus, or bulrushes, Scirpus) or submergent vegetation (pondweed, Potamogeton, water milfoil, Myriophyllum spicatum, hornwort, Ceratophyllum demersum, or muskgrass, Chara). They are most abundant in ponds with high amphipod abundance and intact wetland margins. They are found in freshwater or slightly brackish wetland areas, including ponds, lakes, river impoundments, and coastal bays. Preferred wetlands are fairly shallow. Lesser scaup nest in wetland meadow or grassland areas near ponds.

Habitat Regions: temperate ; freshwater

Terrestrial Biomes: savanna or grassland

Aquatic Biomes: lakes and ponds; rivers and streams; temporary pools; coastal ; brackish water

Wetlands: marsh ; bog

Other Habitat Features: estuarine

Comments: BREEDING: Marshes, ponds, and small lakes (AOU 1998). Usually nests near small ponds and lakes, sedge meadows, creeks; in cover 1-2 ft high, within 46 m of water. Often nest on islands among colonies of gulls or terns. NON-BREEDING: During migration and when not breeding, found along coast in sheltered bays, estuaries, and marshes or inland on lakes, ponds, and rivers; on salt water especially if lakes and ponds frozen. In southern winter range, prefers freshwater ponds, lakes, and sloughs with reasonably clear water 1 m or more deep (Stiles and Skutch 1989).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.

Migrates northward usually in March-April, arriving in far north late May-early June. Departs far north by the end of September, migrates southward through U.S. mainly October-November. Scaup that breed along Beaufort Sea coast winter throughout broad range of central and southern latitudes in North America, from coast to coast.

Lesser scaup adults and young eat insects, crustaceans, and mollusks. They sometimes also take the seeds of aquatic plants, such as yellow pond lily (Nuphar). They forage in shallow, open water by diving. They dive at an angle and surface a few meters from where they dived. They mostly eat prey underwater, but will bring larger prey to the surface to handle it there. Diet varies with the seasonal availability of food and regionally. In breeding lakes amphipods are especially important in the diet. Midges (Chironomidae) and leeches (Hirudinea) are also important in northern lakes. Mollusks and plant seeds become more important at other times of the year and fish and their eggs are taken opportunistically. Seeds become more important in the diet in fall.

Animal Foods: fish; eggs; insects; mollusks; terrestrial worms; aquatic crustaceans

Plant Foods: seeds, grains, and nuts

Primary Diet: carnivore (Insectivore , Eats non-insect arthropods, Molluscivore , Vermivore)

Comments: Feeds on seeds of pondweeds, widgeon grass, wild rice, sedges, bulrushes; also crustaceans, mollusks, and aquatic insects. Diet varies with location. Most feeding occurs in fresh water of various depths, often 3-8 m. In midwinter in Louisiana and in spring and fall in northwestern Minnesota, important foods were crustaceans, insects, and mollusks; in fall, immatures fed heavily on amphipods and did not consume fishes or fingernail clams, which were important in adult diets; by dry weight, animal foods comprised over 90% of the diet in fall and spring, 61% in midwinter (Afton et al. 1991). During fall migration in Ontario, fed in large numbers on zebra mussels (Dreissena) (Wormington and Leach 1992).

Lesser scaup are important predators of aquatic invertebrates in northern boreal lakes. Eggs and hatchlings are taken by a wide range of terrestrial, avian, and aquatic predators. They are susceptible to a range of diseases and parasites. Recorded diseases include avian influenza A, avian cholera (Pasteurella multocida), avian botulism, and aspergillosis (Aspergillus fumigatus). Lesser scaup host a number of scaup specific helminth parasites, including, including gizzard worms (Streptocara crassicauda). Other parasites include renal coccidia (Eimeria species), blood parasites (Leucocytozoon simondi and Haemoproteus nettionis), and g.Sarcocystis> species. Leeches (Theromyzon rude) are often found on the nasal membranes of lesser scaup.

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.

Commensal/Parasitic Species:

• gizzard worms (Streptocara crassicauda)
• renal coccidia (Eimeria)
• blood parasites (Leucocytozoon simondi)
• blood parasites (Haemoproteus nettionis)
• (Sarcocystis)
• leeches (Theromyzon rude)
• redheads (Aythya americana)
• gadwall (Anas strepera)
• canvasbacks (Aythya valisineria)
• white-winged scoters (Melanitta fusca)
• ruddy ducks (Oxyura jamaicensis)
• red-breasted mergansers (Mergus serrator)

Ducklings that are attacked by predators try to stay together and females will try to protect their young, but often their defenses aren't sufficient. Females try to keep their young near the cover of vegetation and the cryptic coloration of ducklings may help to protect them. Adults may feign death when taken 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 terrestrial predators mentioned, along with striped skunks and coyotes, when on the nest. Adults are also taken by snapping turtles, red-tailed hawks, peregrine falcons, snowy owls and bald eagles.

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.

Known Predators:

• American mink (Neovison vison)
• raccoons (Procyon lotor)
• red foxes (Vulpes vulpes)
• American crows (Corvus brachyrhynchos)
• ring-billed gulls (Larus delawarensis)
• California gulls (Larus californicus)
• common ravens (Corvus corax)
• American badgers (Taxidea taxus)
• black-billed magpies (Pica pica)
• great horned owls (Bubo virginianus)
• black-crowned night herons (Nycticorax nycticorax)
• Swainson's hawks (Buteo swainsoni)
• American coots (Fulica americana)
• Arctic loons (Gavia arctica)
• striped skunks (Mephitis mephitis)
• coyotes (Canis latrans)
• snapping turtles (Chelydra serpentina)
• red-tailed hawks (Buteo jamaicensis)
• peregrine falcons (Falco peregrinus)
• snowy owls (Nyctea scandiaca)
• bald eagles (Haliaeetus leucocephalus)

Anti-predator Adaptations: cryptic

NON-BREEDING: usually in flocks on open water (Ridgely and Gwynne 1989).

Lesser scaup use a set of visual displays, sometimes accompanied by vocalizations, 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. Lesser scaup are fairly quiet animals. Males give a soft call during courtship and a whistle during mating displays that accompanies their visual display. Females also make a soft "arrr" sound during courtship, which signals her interest in a particular male. Females make a "purrrr" call that is directed towards predators and is also used to attract the help of their male mates when they are flying from the nest to a pond. Males then keep other males away that might harass the female.

Communication Channels: visual ; acoustic

Most mortality occurs within the first few weeks of hatching as a result of predation and cold stress. Ducklings that are hatched from larger eggs and later in the season have higher survival rates, so nutrient reserves influence survival. Lesser scaup seem to have a flexible reproductive strategy that allows them to take advantage of temporally variable resources to maximize reproductive success. The maximum recorded lifespan in the wild is 18 years, 4 months. Annual mortality estimates range from 32 to 71%.

Range lifespan

Status: wild: 18.33 (high) years.

Lesser scaup are monogamous. Mate-switching is common during the breeding season. Pairs are formed during late spring migration and last only until the females have been incubating the eggs for some time. Forced extra-pair copulations are common.

Mating System: monogamous

Lesser scaup are one of the latest nesting ducks in North America. Most individuals arrive on breeding grounds by May and nesting and egg-laying activity peaks in June. Nesting is highly synchronous across large geographic areas. Females and males start the nest as a scrape 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. Larger clutches are found in southern populations than in northern populations. Males abandon their female mates on the nest in mid to late June, about mid-way through incubation, which lasts 21 to 27 days. Lesser scaup ducklings that hatch from larger eggs and later in the season have higher survival rates than others. It is thought that lesser scaup breed later in the season than other North American ducks in order to take best advantage of amphipod prey abundance, which increases later in the season. Young can fly 47 to 61 days after hatching. Males and females can breed in the first year after hatching, although breeding may be delayed in unfavorable years.

Breeding interval: 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: 8-10.

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.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)

Only females incubate the eggs and care for the young after hatching. Males abandon females during the incubation phase. Young are precocial at hatching and can feed themselves. Females lead their brood away from the nest within a day of hatching. Young feed from the water surface initially, but feed by diving by 2 weeks old. Females attend their brood for 2 to 5 weeks after hatching, often abandoning them 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)

Egg-laying begins in early May in the south to mid-June in the north. Clutch size: 6-15 (usually 9-12, largest in older females). Incubation: 22-27 days, by female (Terres 1980). Young are tended by female. Variable percentage of yearling females do not breed.

Lesser scaup are considered least concern by the IUCN because of their large population sizes and geographic range. They are one of the most abundant duck species in North America. However, regional population declines have been documented and some populations may be susceptible to habitat degradation (such as wetland destruction) and pollution. High levels of selenium have been detected in the livers of lesser scaup in the Great Lakes region, but not in other regions where research has been conducted to date. Research on female body condition just prior to egg laying in North America suggests that nutrient stress is resulting in lower reproductive success in North America.

US Migratory Bird Act: protected

US Federal List: no special status

CITES: no special status

State of Michigan List: no special status

IUCN Red List of Threatened Species: least concern

Canada

Rounded National Status Rank: N5B,N5N : N5B: Secure - Breeding, N5N: Secure - Nonbreeding

United States

Rounded National Status Rank: N5B,N5N : N5B: Secure - Breeding, N5N: Secure - Nonbreeding

Rounded Global Status Rank: G5 - Secure

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

Lesser scaup are important members of North American wetland ecosystems. They are also hunted during migration.

Positive Impacts: food ; body parts are source of valuable material