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Heteronetta atricapillablack-headed duck

By Joseph Boss

Geographic Range

Heteronetta atricapilla is found in South America in southern Brazil, Chile, and Argentina. Heteronetta atricapilla is a partially migratory species. Northern breeding populations are sedentary, while southern breeding populations migrate north during the austral winter. These southern populations migrate into Bolivia, southern Brazil, and Uruguay. ("Heteronetta atricapilla", 2004; "Biodiversity.mongabay.com", 2006)

Habitat

Black-headed ducks are found in marshes, bogs, swamps, fens, peatlands, and permanent freshwater lakes. Black-headed ducks are found in terrestrial environments and semipermanent marshes containing a large amount of plant life. ("Biodiversity.mongabay.com", 2006)

  • Aquatic Biomes
  • lakes and ponds
  • coastal

Physical Description

Black-headed ducks are blackish-brown on their breast and underside, with black heads, wings, and backs. The upper mandible is black with a yellow edge and the lower mandible is dark yellow. Black-headed ducks have dark grey legs with yellowish-green shading along the tarsi. Adult females are larger than males. Wings of adults are flecked with small, white spots or they are solid grey-brown. Juvenile ducks are distinguished from adults by having a lighter colored vertical line above the eye, extending from the eye to the crown. ("Answers.com", 2006; Hohn, 1975; Weller, 1967)

Black-headed ducks moult twice each year. In August and September birds moult into their nuptial plumage. In December and January the nuptial plumage replaces the winter (non-nuptial) plumage. (Weller, 1968)

  • Sexual Dimorphism
  • female larger
  • Range mass
    434 to 630 g
    15.30 to 22.20 oz
  • Average mass
    538.9 g
    18.99 oz
  • Range length
    35 to 40 cm
    13.78 to 15.75 in

Reproduction

During courtship, males stretch their neck by inflating the bilateral cheek pouches and the upper esophagus in order to attract female mates. Black-headed ducks are promiscuous, with both males and females taking multiple mates during the breeding season. (Hohn, 1975)

Black-headed ducks are brood parasites. Females lay their eggs in the nests of other species. Black-headed ducks deposits their eggs in nests around 1 meter above the water and lay 2 eggs, on average, per nest. Egg survival rate is around a third of the total number of eggs laid. Black-headed ducks breed twice a year, in fall and spring. ("Answers.com", 2006; Hohn, 1975; Rees and Hillgarth, 1984)

  • Breeding interval
    Black-headed ducks breed twice yearly.
  • Breeding season
    Black-headed ducks breed in fall and spring.
  • Average eggs per season
    4
  • Average time to hatching
    21 days
  • Average time to independence
    several hours

Black-headed ducks do not build nests or incubate their eggs; instead they are brood parasites and rely on other duck species for these tasks. Black-headed duck adults and newborn chicks do not harm the eggs or chicks of the host species. The eggs are incubated for approximately 21 days by their hosts. A few hours after hatching, black-headed duck chicks are capable of walking and feeding on their own. ("Answers.com", 2006; Rees and Hillgarth, 1984)

  • Parental Investment
  • no parental involvement
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female

Lifespan/Longevity

Specific information on black-headed duck lifespan and longevity was not available. However, survival of other members of the family Anatidae is variable. From 65 to 80% of ducklings die in their first year. After this crucial year, survival rate increases. Most birds that reach adulthood live for only another 1 to 2 years. The maximum recorded lifespan within the family Anatidae is 28 years. ("The Sibley Guide to Bird Life and Behavior", 2001)

Behavior

Black-headed ducks are migratory, flying in flocks of up to 40 birds. Black-headed ducks feed mostly in early morning, rest on land in the daytime, and swim mostly during the evening. During the evening male and female black-headed ducks patrol nearby nest sites searching for suitable hosts. Preferred host nests are coots, since their nests are common in marshy areas. (Rees and Hillgarth, 1984; Weller, 1968)

Home Range

Since black-headed ducks do not make nests, they are not territorial. They move throughout a large range in order to search for host nests and do not stay within any particular home range. (Rees and Hillgarth, 1984; Weller, 1968)

Communication and Perception

Male black-headed ducks communicate with potential mates by stretching their necks, they also use vocalizations to some extent. (Hohn, 1975)

Food Habits

Black-headed ducks feed mostly in the morning by diving, head-dipping, dabbling, and mud-filtering. Black-headed ducks eat mostly plant material, such as seeds, underground tubers, green herbaceous foliage of aquatic grasses and sedges, sea grasses, and submerged pond weeds. They may also eat some aquatic invertebrates. ("Answers.com", 2006; "The Sibley Guide to Bird Life and Behavior", 2001; Rees and Hillgarth, 1984)

  • Animal Foods
  • insects
  • aquatic crustaceans
  • Plant Foods
  • leaves
  • roots and tubers
  • seeds, grains, and nuts

Predation

The main predators of black-headed duck young are other ducks whose nests have been parasitized by black-headed ducks. Almost half of their eggs die because host ducks recognize the eggs and destroy them. Black-headed duck eggs are not camouflaged; they are white and quite conspicuous. Black-headed ducks are hunted by humans for food and plumage. Adults may also be preyed on by large predators such as raptors. Their dark feather color and patterning helps to camouflage them in wetland vegetation. ("Answers.com", 2006; "Answers.com", 2006; Weller, 1968)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Black-headed ducks are brood parasites, they rely on other duck species to incubate and provide shelter for their eggs. This negatively affects the hosts since the host species must allocate energy to hatch the foreign eggs, which may result in a lower number of their own eggs hatching and their own hatchlings surviving to adulthood. ("Answers.com", 2006)

Species Used as Host

Economic Importance for Humans: Positive

Humans hunt black-headed ducks for food and for use of their plumage. ("Answers.com", 2006)

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

Economic Importance for Humans: Negative

There are no known adverse effects of black-headed ducks on humans.

Conservation Status

Black-headed ducks are not currently considered at risk, but may be threatened by habitat loss, hunting, and pollution. ("Answers.com", 2006)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Joseph Boss (author), Kalamazoo College, Ann Fraser (editor, instructor), Kalamazoo College.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

bog

a wetland area rich in accumulated plant material and with acidic soils surrounding a body of open water. Bogs have a flora dominated by sedges, heaths, and sphagnum.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

diurnal
  1. active during the day, 2. lasting for one day.
endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

parasite

an organism that obtains nutrients from other organisms in a harmful way that doesn't cause immediate death

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

References

Chanticleer Press, Inc. 2001. The Sibley Guide to Bird Life and Behavior. New York: Alfred A. Knopf.

Answers Corporation. 2006. "Answers.com" (On-line). Black-headed Duck. Accessed November 07, 2006 at http://www.answers.com/topic/black-headed-duck.

Mongabay.com. 2006. "Biodiversity.mongabay.com" (On-line). Heteronetta atricapilla. Accessed October 13, 2006 at http://biodiversity.mongabay.com/animals/h/Heteronetta_atricapilla.html.

International Union for Conservation of Nature and Natural Resources. 2004. "Heteronetta atricapilla" (On-line). 2006 IUCN Red List of Threatened Species. Accessed October 13, 2006 at http://www.iucnredlist.org/search/details.php/10011/summ.

Hohn, E. 1975. Notes on black-headed ducks, painted snipe. The Auk, 92: 566-575. Accessed October 13, 2006 at http://elibrary.unm.edu/sora/Auk/v092n03/p0566-p0575.pdf.

Rees, E., N. Hillgarth. 1984. The breeding biology of captive black-headed ducks and the behavior of their young. Condor, 86(3): 242-250. Accessed November 07, 2006 at http://links.jstor.org/sici?sici=0010-5422%28198408%2986%3A3%3C242%3ATBBOCB%3E2.0.CO%3B2-N&size=LARGE.

Weller, M. 1968. Notes On some Argentine anatids. The Wilson Bulletin, 80(2): 189-212. Accessed October 13, 2006 at elibrary.unm.edu/sora/Wilson/v080n02/p0189-p0212.pdf.

Weller, M. 1967. Notes on plumages and weights of the black-headed duck, Heteronetta atricapilla . The Condor, 69(2): 133-145. Accessed October 13, 2006 at http://links.jstor.org/sici?sici=0010-5422%28196703%2F04%2969%3A2%3C133%3ANOPAWO%3E2.0.CO%3B2-Q&size=LARGE.

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