Animal Diversity Web

Ge­o­graphic Range

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. (Austin, et al., 1998)

• Biogeographic Regions
• nearctic
  • native
• neotropical
  • native

Habi­tat

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. (Austin, et al., 1998; Lin­de­man and Clark, 1999)

• 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

Phys­i­cal De­scrip­tion

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. (Austin, et al., 1998)

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. (Austin, et al., 1998)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

• 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

Re­pro­duc­tion

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. (Austin, et al., 1998)

• 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. (Austin, et al., 1998; Daw­son and Clark, 1996)

• Key Reproductive Features
• iteroparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• oviparous

• 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

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. (Austin, et al., 1998)

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

Lifes­pan/Longevity

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%. (Austin, et al., 1998)

• Range lifespan
  Status: wild

  18.33 (high) years

Be­hav­ior

Lesser scaup are so­cial, non-ag­gres­sive birds. They are tol­er­ant of con­specifics ex­cept for the early breed­ing sea­son, when males de­fend their fe­male mates. 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, for­ag­ing for about 20 min­utes at a time through­out the day. (Austin, et al., 1998)

• Key Behaviors
• flies
• natatorial
• diurnal
• motile
• nomadic
• migratory
• social

Home Range

Breed­ing pairs do not de­fend ter­ri­to­ries, in­stead they have small, over­lap­ping home ranges that change in size through­out the breed­ing sea­son. Home range sizes are from 26 to 166 hectares. In win­ter lesser scaup may be some­what no­madic. Fe­males re­turn to their natal range in sub­se­quent years, males do not. (Austin, et al., 1998)

Com­mu­ni­ca­tion and Per­cep­tion

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. (Austin, et al., 1998)

• Communication Channels
• visual
• acoustic

• Perception Channels
• visual
• tactile
• acoustic
• chemical

Food Habits

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.

• Primary Diet
• carnivore
  • insectivore
  • eats non-insect arthropods
  • molluscivore
  • vermivore

• Animal Foods
• fish
• eggs
• insects
• mollusks
• terrestrial worms
• aquatic crustaceans

• Plant Foods
• seeds, grains, and nuts

Pre­da­tion

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. (Austin, et al., 1998)

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.

• Anti-predator Adaptations
• cryptic

• 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)

Ecosys­tem Roles

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. (Austin, et al., 1998)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

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

• Positive Impacts
• food
• body parts are source of valuable material

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

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

Con­ser­va­tion Sta­tus

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. (An­teau and Afton, 2004; BirdLife In­ter­na­tional 2008, 2008; Custer, et al., 2003; Lin­de­man and Clark, 1999)

• IUCN Red List

  Least Concern
  More information

• IUCN Red List

  Least Concern
  More information

• US Migratory Bird Act

  Protected

• US Federal List

  No special status

• CITES

  No special status

• State of Michigan List

  No special status

Other Com­ments

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

Con­trib­u­tors

Tanya Dewey (au­thor), An­i­mal Di­ver­sity Web.

Ref­er­ences

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 http://​www.​iucnredlist.​org/​details/​141551.

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.