The Black-Headed Duck – A South American Anatidae

Much like a typical duck, its plumage and other features suggest not a parental relationship, but a convergent evolution in the ancestors of stiff-tailed ducks. It is a small dark duck: the male has a black head and coat, and a lighter side and belly, while the female is uniformly light brown. They live in lakes and swamps in northern Chile, Paraguay and northern Argentina and feed on aquatic plants and insects.

They place their nests into the nesting sites of other birds, in particular the Rosy-billed pochard (Netta peposaca), but also of other ducks and sometimes even of gulls and birds of prey. However, unlike the cuckoos, they do not destroy the eggs, nor do they kill adults and chicks of their host. It is the sole member of the whole Heteronetta genus in the world.

These migratory ducks can be seen flying in flocks counting up to 50 birds. They like to feed early in the morning, and spend the rest of their daytime resting on land, while the evening is dedicated to swimming. In the evening, couples of black-headed ducks will roam around the nest sites in the area, looking for a suitable host. Since they don’t make their own n

ests, black-headed ducks are not territorial but move over a large range, searching for host nests and tend to not stay in any home range per season.

Their communication and perception channels are both visual and acoustic. Male black-headed ducks stretch their necks while doing some vocalizations to reach out to potential partners. Their chicks main predators are the ducks whose nests have been occupied by the Heteronetta atricapilla, in fact half of its eggs will die, destroyed by the host when it’ll recognize the eggs. Black-headed duck are white and don’t camouflage too well, they’re hunted by men for their meat and plumage. Their dark feather pattern works better to hide in the wetland grass.

Being parasites, they very much depend on other ducks to take care and incubate their eggs. This has negative effects on the host, as it has to spend energy on eggs that aren’t it’s own and can ultimately result in seeing less of its own eggs hatch and less of their own chicks making it to adulthood.

• Scientific name: Heteronetta atricapilla.
• Weight: 434 – 640 g.
• Length: 35 – 40 cm.
• Age: There’s a lack on information on the Heteronetta atricapilla lifespan. Up to 80% of the ducklings will die in the first year of their life. Survival rate increases slightly after this year and the birds reaching adulthood will live up for another 2 years maximum. The longer ever lifespan recorded in the Anatidae family is of 28 years.
• Diet: Herbivore mainly, it eats leaves, tubers, nuts, grains and roots, but it feeds also on crustaceans and insects.
• Habitat: Tropical coastal areas, lakes and ponds but also wetlands such as swamps, marches and bogs. They’re comfortable in both salt water and fresh water environments as well as terrestrial ones.
• Threats: Pollution, hunting and loss habitat are threatening the Black-headed duck, among its predators there are not only humans but also their duck hosts, coots and Falconiformes.

Black-headed ducks are brownish-black on their chest and underside, black back, wings and head – obviously. Their beak is dark yellow and black, dark grey legs with a green shading on their feet. Adult females are easily recognizable as they’re typically bigger than the males. In the adult, the wings feature small white spots that can sometimes be brownish-grey. The young specimens differ from the adults by the lighter colored line right above the eye pointing up to the crown of the head. Black-headed ducks molt two times a year, into the nuptial plumage between August and September and then in December and January, it takes the places of the winter plumage.

Black-headed ducks are present in lower South America, in Paraguay, Uruguay, Chile, Argentina, Bolivia and in some parts of southern Brazil. This species only partially migrates, the populations living in the north are sedentary, while the southern breeding birds head north for the austral winter migration into Bolivia, Uruguay and Brazil. Black-headed ducks can be observed in marshes, fens, swamps and lakes. They are often found on land in marshes with plenty of plant based food.

Black-headed ducks feed early in the morning, they do so by diving head down, filtering the mud. They eat plant material and underground tubers, aquatic grass, sea grass, weeds, green foliage and seeds. Sometimes they can also aquatic crustaceans and invertebrates.

Male will elongate their neck and inflate the cheek and chest to impress the female partners during courtship. Their mating system is promiscuous, meaning that both partners will mate with many males and females throughout the duration of the reproductive period.

Being nest parasites, females of black-headed ducks will lay their eggs in other’s. The nests they are after are about 1 meters above the level of the water and an average of two eggs is laid per nest. The survival rate is low, only a third of the total. Breeding happen two times a years, in spring and fall.

Even though black-headed ducks don’t bother to make their nest and instead depend on other birds for nesting and incubating, they won’t harm the newborn or the eggs of their host. The incubation by the nest host lasts for about 3 weeks. Shortly after hatching, the chicks of Heteronetta atricapilla are already able to walk around and feed on their own.

Black-headed ducks are classified as Least Concern (LC) in the IUCN Red List and aren’t considered at risk at the moment. But pollution and habitat loss may be serious threats for this species in the future. Black-headed ducks are hunted by men for their meat and for their plumage and this as well can result in a drop in their numbers.