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
Nomonyx dominicus
Masked Duck
(Linnaeus, 1766)
Detailed Texts Multi-lang
A small, secretive waterfowl with a compact body and a stiff tail that often cocks upward. Breeding males have a striking black face mask contrasting with a rich cinnamon-rufous body mottled with black, and a brilliant sky-blue or cobalt bill. Females and non-breeding males are warm buffy-brown with two distinctive dark horizontal stripes running across the pale face.
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.Nomonyx
Taxonomic AuthorityThe scientist who first formally described and published this species, followed by the year of publication.(Linnaeus, 1766)
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
Inhabits heavily vegetated, freshwater wetlands, including shallow marshy ponds, swamps, sluggish rivers, rice fields, and temporary pools densely covered with water lilies and emergent reeds. It heavily avoids open, clean water areas lacking cover.BehaviourDaily activity patterns, movement, territory use, foraging style, and seasonal behavioral changes. Multi-lang
An extremely cryptic and shy species that spends the day hidden beneath overhanging bank vegetation or water lily pads. It is predominantly active during twilight or at night. When threatened, it prefers to dive or freeze silently instead of flying. Vocalizations are rare, consisting of a low, repetitive guttural cooing or clucking sound: 'kerr-kerr-kerr'.Social ActivitySocial structure: whether the species is solitary, paired, or colonial; hierarchy and communication. Multi-lang
Generally solitary or found in tightly bonded monogamous pairs. Unlike many other anatids, they do not form large flocks, though small temporary groups of up to 20 individuals may aggregate during dry seasons when water levels drop significantly.Feeding GuildWhat the species eats, how it forages or hunts, and its role as a consumer in the food web. Multi-lang
Aquatic surface-diving omnivore.Trophic Chain DetailsSpecific interactions in local food webs: prey species, predators, competitors, and scavengers. Multi-lang
An omnivorous waterbird that feeds by diving or dabbling among floating mats of vegetation. Its diet consists of seeds, roots, and leaves of aquatic plants (especially water lilies), heavily supplemented by aquatic insects, small crustaceans, snails, and dragonfly nymphs. Predators include large raptors, anacondas, caimans, and marsh foxes.Reproductive BehaviourMating strategies, courtship displays, nesting or spawning behavior, and parental care. Multi-lang
Monogamous pairs nest isolated inside dense vegetation. The female constructs a well-concealed, bulky cup nest woven from dead leaves and rushes, attached to emergent reeds just inches above the water or resting on floating vegetation mats, often adding a woven dome. She lays 3 to 6 large, buff-colored eggs and lines the nest with down feather fibers.Physical Measures
Length (cm)
30.0 - 36.0 cm
Weight (Grams)
300 g - 450 g
Offspring per cycleTypical number of young (live births, eggs, or seeds) produced by one adult in a single reproductive event or breeding season.3 - 6
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.
10 - 12 Months
Gestation / IncubationDuration from fertilization to birth (mammals) or to hatching (egg-laying species).
26 - 28
Lifespan EstimatedExpected duration of life from birth to natural death under wild conditions.
Males4 - 7 Years
Females4 - 7 Years
Sexual DimorphismPhysical differences in size, coloration, or morphology between males and females of this species.
Males Multi-lang
The breeding male exhibits an unmistakable jet-black face mask extending from the forehead down to the chin and cheeks. His neck and body feature a rich, vibrant rust or reddish-cinnamon color with prominent black spotting on the mantle, and the bill turns intense sky-blue.
Females Multi-lang
Females are evolutionary designed for visual crypsis, completely lacking the rufous tones and blue bill. They display a uniform brownish-buff body with heavy dark streaking, and their face is cream-colored with two prominent, dark brown horizontal lines slicing across the cheeks.
Evolutionary AdaptationsInherited traits and behaviors that improve the species' survival and reproduction in its specific environment. Multi-lang
Extremely flattened tarsi and feet positioned far back on the pelvic girdle, optimizing high-efficiency underwater diving propulsion but making walking on dry land clumsy and difficult.
Ability to submerge slowly and silently into the water column without leaving a ripple, leaving only its eyes and nostrils exposed among floating vegetation to evade detection.
Main ThreatsDocumented pressures reducing the population: habitat loss, hunting, disease, climate change, and invasive species. Multi-lang
Widespread drainage of temporary wetlands for industrial agricultural conversion and intense pesticide runoff in commercial rice fields, which poisons the aquatic macroinvertebrates they rely on.
Interesting FactsSurprising or notable facts that highlight what makes this species unique or ecologically important. Multi-lang
Unlike typical stiff-tailed ducks that prefer open lakes, the Masked Duck is evolutionary tailored for hidden micro-habitats, behaves more like a rail, and is fully capable of taking off directly into flight without running across water.