AnimaliaHighest rank in taxonomy. Groups all life into domains: Animalia, Plantae, Fungi, etc.IUCN LCInternational Union for Conservation of Nature — the world authority on species extinction risk, using standardized criteria. — Least Concern — widespread and abundant; not at immediate risk of extinction.In ProgressCurrent stage of this record in the editorial review workflow. Recent Sighting
Aythya affinis
Lesser Scaup
(Eyton, 1838)
Detailed Texts Multi-lang
A medium-sized diving duck; breeding males have a dark head with a purplish sheen, a black breast, and a grey back, while females are brown with a white patch at the base of the bill.
Added by
Anonymous Curator
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Under Review
Last modified by
Julia Trouin
TaxonomyBiological classification ranks placing this species within the tree of life, from Kingdom down to Genus.
PhylumRank below Kingdom. Groups organisms sharing a fundamental body plan (e.g., Chordata = vertebrates and some invertebrates).Chordata
ClassRank below Phylum. Subdivides by structural traits (e.g., Mammalia, Aves, Reptilia, Insecta).Aves
OrderRank below Class. Groups related families sharing common ancestry (e.g., Carnivora, Primates).Anseriformes
FamilyRank below Order. Groups closely related genera (e.g., Felidae = cats, Canidae = dogs).Anatidae
GenusRank just above Species. The first word in the two-part binomial scientific name.Aythya
Taxonomic AuthorityThe scientist who first formally described and published this species, followed by the year of publication.(Eyton, 1838)
Record Completeness
96%Coming soon
Ecology & StatusHow this species lives: habitat preferences, diet, behavior, population status, and role in its ecosystem.
OriginWhether the species is native (evolved here), endemic (found only here), or introduced by human activity.
Native
Population TrendDirection of change in population size over time: increasing, stable, decreasing, or unknown.
Decreasing
Breeding SeasonTime of year when this species typically reproduces or flowers.
Year Round
Trophic RolePosition in the food chain: producer, herbivore, carnivore, omnivore, decomposer, or parasite.
Omnivore
Recent SightingsWhether this species has been observed in the wild in Costa Rica within recent years.
Yes
Habitat SummaryOverview of the specific ecosystems and environments where this species is found in Costa Rica. Multi-lang
Breeds in wetlands, marshes, and ponds within boreal forests and prairies, migrating south to winter on large lakes, estuaries, and coastal lagoons.BehaviourDaily activity patterns, movement, territory use, foraging style, and seasonal behavioral changes. Multi-lang
A highly migratory duck that travels in large flocks. It is an accomplished diver, spending most of its active time on open bodies of water, diving down to several meters to forage on the bottom substrate.Social ActivitySocial structure: whether the species is solitary, paired, or colonial; hierarchy and communication. Multi-lang
Highly gregarious during migration and winter, often mixing freely with Greater Scaups and Ring-necked Ducks to form immense, dense floating assemblies on expansive water bodies.Feeding GuildWhat the species eats, how it forages or hunts, and its role as a consumer in the food web. Multi-lang
Aquatic diving omnivore / invertivore.Trophic Chain DetailsSpecific interactions in local food webs: prey species, predators, competitors, and scavengers. Multi-lang
Consumes aquatic macroinvertebrates such as molluscs, snails, crustaceans, and insect larvae, alongside aquatic plants. It is preyed upon by eagles, large falcons, and large predatory fish, while eggs are taken by gulls and minks.Reproductive BehaviourMating strategies, courtship displays, nesting or spawning behavior, and parental care. Multi-lang
Forms monogamous pairs seasonally. The female builds a shallow scrape nest lined with down and grasses on the ground, heavily hidden in vegetation near water. She incubates the eggs and leads the precocial chicks alone.Physical Measures
Length (cm)
38.0 - 45.0 cm
Weight (Grams)
550 g - 1.00 kg
Offspring per cycleTypical number of young (live births, eggs, or seeds) produced by one adult in a single reproductive event or breeding season.6 - 14
Sexual DimorphismObservable physical differences between males and females of the same species (e.g., size, coloration, features).Yes
Lifespan
Sexual MaturityAge at which the individual becomes capable of reproducing for the first time.
1 - 2 Years
Gestation / IncubationDuration from fertilization to birth (mammals) or to hatching (egg-laying species).
21 - 25
Lifespan EstimatedExpected duration of life from birth to natural death under wild conditions.
Males5 - 14 Years
Females5 - 14 Years
Sexual DimorphismPhysical differences in size, coloration, or morphology between males and females of this species.
Males Multi-lang
Breeding males feature an iridescent dark head with a purplish gloss, a jet-black breast, white flanks, and a finely vermiculated greyish back.
Females Multi-lang
Females are structurally similar but have an overall dull dark brown plumage with a prominent, well-defined white patch encircling the base of the bill.
Evolutionary AdaptationsInherited traits and behaviors that improve the species' survival and reproduction in its specific environment. Multi-lang
Large webbed feet positioned far back on the body provide powerful propulsion for deep diving and underwater foraging.
Highly dense, waterproof plumage traps air to insulate the bird effectively against freezing water temperatures.
Main ThreatsDocumented pressures reducing the population: habitat loss, hunting, disease, climate change, and invasive species. Multi-lang
Vulnerable to wetland degradation, water pollution from heavy metals, oil spills in wintering coastal areas, and climate change altering northern breeding habitats.
Interesting FactsSurprising or notable facts that highlight what makes this species unique or ecologically important. Multi-lang
They gather in spectacular winter aggregations called 'rafts', which can contain tens of thousands of individuals clustered tightly on open waters.