Definitions

screamer

screamer

[skree-mer]
screamer, common name for gregarious, aquatic birds comprising three species in the family Anhimidae. Although they are related to the ducks and geese, they do not resemble them in outward appearance. Screamers possess some unusual anatomical features, such as a layer of insulating air cells that separate the outer skin from the body. This feature is also seen in the pelicans. They share another peculiarity solely with colies, penguins, and ostriches—their feathers grow over the body without any bare spaces (called apteria) in between. Another peculiarity of the screamers is their hollow bones. Finally, they lack particular rib bones that are functional as strengthening elements in all other birds except the extinct Archaeopteryx. The turkey-sized horned screamer (Anhima cornuta) is the largest of the family. It is distinguished by a 3- to 4-in. (8- to 10-cm) hornlike projection on its forehead and by two sharp wing spurs. A creature of the wetlands and tropical rain forest, it is found throughout most of South America. The slightly smaller crested screamer (Chauna torquata) is native to swamps and plains from Brazil to N Argentina. It is distinguished by a short, feathered neck crest. The swan-sized black-necked screamer (C. chavaria) of N Colombia and Venezuela is the smallest and darkest of the family. Using their short, conical, fowllike bills, screamers feed primarily on a vegetable diet of succulent grasses and seeds, although the horned screamer occasionally eats insects as well. Screamers are strong fliers and generally roost in trees. However, their delicate, shallow nests of rushes are built on the water or in marshes. Their white or buffy eggs number from two to six per clutch. Both sexes share incubation duties. The chicks are downy and resemble baby swans. Screamers are classified in the phylum Chordata, subphylum Vertebrata, class Aves, order Anseriformes, family Anhimidae.

The Screamers are a small family of birds, the Anhimidae. For a long time they were thought to be related to the Galliformes because of similar bills, but they are truly related to ducks (family Anatidae), most closely to the Magpie-goose (which some DNA evidence suggests are closer to screamers than to ducks).

The three species occur only in South America, ranging from Venezuela to northern Argentina. They are large, bulky birds, with a small downy head, long legs and large feet which are only partially webbed. They have large spurs on their wings which are used in fights over mates and territorial disputes, these can break off in the breast of other screamers, and are regularly renewed. Unlike ducks they have a partial moult, and are able to fly throughout the year. They live in open areas and marshes with some grass and feed on water plants. One species, the Southern Screamer, is considered a pest as it raids crops and competes with farm birds.

Screamers lay between 2 to 7 white eggs, with four or five being typical. The young, like those of most Anseriformes, can run as soon as they are hatched. The chicks are usually raised in or near water as they can swim better than they can run. This helps them to avoid predators. Like ducks, screamer chicks imprint early in life. This, coupled with their unfussy diet makes them amenable to domestication. They make excellent watchdogs due to their loud screams when encountering anything new and potentially threatening.

It is uncertain whether the three screamer species are endangered or declining. They are seldom hunted, in spite of their conspicuous nature, because their flesh has a spongy texture and is riddled with air-sacs, making it highly unpalatable. The main threats are habitat destruction and increased intensification of agriculture, but the extent of this is unknown.

Species

References

Bibliography

  • Carboneras, C. (1992). Family Anhimidae (Screamers). Pp.528-535 in; del Hoyo, J., Elliott, A. & Sargatal, J. eds. Handbook of the Birds of the World, Vol 1, Ostrich to Ducks. Lynx Edicions, Barcelona. ISBN 8487334091

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