Birds
Black-headed Duck
Heteronetta atricapilla
A female black-headed duck never builds a nest of her own, instead laying every egg she produces into the nests of other waterbirds, the only duck species known to rely entirely on this brood-parasitic strategy.
Overview
The black-headed duck, Heteronetta atricapilla, is a Least Concern waterbird of freshwater marshes across southern South America. It holds a unique distinction among all duck species: it is an obligate brood parasite, laying its eggs exclusively in the nests of other birds and providing no direct parental care of its own.
An unusual strategy with low cost
Unlike brood parasites such as cuckoos, the black-headed duck’s precocial chicks do not harm host eggs or nestlings and become independent almost immediately after hatching, making its parasitic strategy unusually low-cost for the host species it relies on.
Status
Least Concern, remaining widespread across suitable freshwater marsh habitat throughout southern South America.
Black-headed Duck: common questions
Why is the black-headed duck unusual among ducks?
It is the only duck species known to be an obligate brood parasite, laying every egg in the nests of other birds and never building a nest or raising young of its own.
Which species does the black-headed duck parasitize?
It lays eggs in the nests of a wide range of waterbirds, including coots, gulls, and even some birds of prey, relying on the host parents to incubate its eggs.
Does the black-headed duck harm its host species?
Not significantly. Unlike brood parasites such as cuckoos, its chicks do not push out host eggs or nestlings, and ducklings become independent almost immediately after hatching, limiting the cost imposed on host parents.
How independent are black-headed duck chicks?
Extremely independent. Chicks are precocial and typically leave the host nest within a day or two of hatching, finding food and avoiding danger largely on their own from the start.