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Biology of blackbirds

Species of blackbirds

Blackbirds and humans


The blackbird family (Icteridae) consists of about 100 medium-sized species of birds that occur only in the Americas. Blackbirds are found in widespread habitats, ranging from wetlands, to prairies, to forests. The most common members of the family are various species of blackbirds, grackles, cowbirds, orioles, meadowlarks, bobolink, and others.

Biology of blackbirds

Blackbirds tend to have conical shaped, pointed beaks. Most species are sexually dimorphic, particularly the relatively northern, migratory species. Males often have brilliant hues in their plumage and are commonly iridescent, while female blackbirds are usually relatively drab and cryptically marked. Some male blackbirds incorporate splendid yellow, orange, and red colors in their plumage.

Some species of the blackbirds are accomplished vocalists, displaying a complex repertoire of loud and clear whistles and calls. Orioles are among the most musical of the blackbirds, producing rather pleasing, flute-like melodies.

Species of blackbirds

Blackbirds exploit a wide range of habitats. Most species occur in tropical forests of various sorts, but virtually all types of terrestrial and wetland habitats are utilized by some species. In North America, the northern oriole (Icterus galbula ) is a species of open forests, where it builds its characteristic, pendulous

nests, often in elm trees. The bobolink (Dolichonyx oryzivorus ) and meadowlarks (Sturnella spp.) are more typical of open grasslands and prairies, while the red-winged blackbird (Agelaius phoeniceus ) and yellow-headed blackbird (Xanthocephalus xanthocephalus ) are typical of marshes and some other wet habitats.

The most widespread species is the red-winged blackbird, which ranges from the subarctic to Central America. This common and familiar bird breeds in tall marshes and other wet places. The male red-winged blackbird is colored as its name implies, with a jet-black body and richly red epaulets on the shoulders. Female red-winged blackbirds have a streaky, brown plumage, and look much like large sparrows. After the breeding season, red-winged blackbirds aggregate into large flocks that forage widely for small grains, and can cause agricultural damage. Red-winged blackbirds generally spend the winter in these flocks, mostly in southern parts of their range, where they forage during the day and roost communally at night in woodlands and marshes.

The most northerly blackbird is the rusty blackbird (Euphagus carolinus ), which in some places breeds as far as the limits of the mainland in the western Arctic. The most southerly species is the red-breasted blackbird (Leistes militaris ) of the Falkland Islands.

Blackbirds that breed in the north are migratory. The longest migrations are undertaken by the bobolink. This species breeds in prairies and hayfields as far north as southern Canada, and winters in pampas and other grasslands as far south as Argentina. Tropical members of the blackbird family are not migratory, but they may undertake local, seasonal movements.

Cowbirds, such as the brown-headed cowbird (Molothrus ater ) of North America, are species of open habitats. As their name implies, these birds often associate with grazing livestock, feeding on insects that these animals flush as they move through vegetation. Cowbirds have an unusual breeding strategy. Instead of building their own nest and raising their young, cowbirds are nest parasites. They surreptitiously lay single eggs in the nests of other species, and sometimes remove eggs of the host bird. If the host birds do not recognize the cowbird egg as being alien, they will brood it and care for the hatchling until it fledges. Many of the approximately 200 species of birds known to be parasitized by the brown-headed cowbird are relatively small, such as vireos, warblers, and thrushes. The nestlings of these birds suffer as a result of the disproportionate demands placed by the voracious cowbird chick on its foster parents, and in many cases this causes the reproductive effort of the host birds to fail. The cowbird chick develops rapidly, and can fly in only nine or ten days after hatching.

The blackbird (Turdus merula ) of Europe, is actually a member of the thrush family, Turdidae.

Blackbirds and humans

Cowbirds are considered to be an important pest in those parts of North America to which the species has expanded its range as a result of the fragmentation of the initially forested landscape by humans. Birds in those regions tend not to be well adapted to cowbird parasitism, and the reproductive success of their populations can be markedly reduced by this relationship. In some cases, cowbirds are sought out and killed by conservation biologists, in order to reduce the negative impact of parasitism on rare and endangered species of birds, such as the Kirtlands warbler (Dendroica kirtlandii ) of Michigan.

Some species of blackbirds are highly gregarious, especially during autumn and winter when they aggregate into flocks that can contain millions of birds. Winter flocks of the red-winged blackbird are sometimes regarded as an agricultural nuisance because of damages caused to fields of winter wheat and some other crops. Sometimes, pest-control actions are mounted against these flocks, and millions of these native birds may be killed when they are sprayed with chemicals at their communal roost sites.



Forshaw, Joseph. Encyclopedia of Birds. 2nd ed. New York: Academic Press, 1998.

Jaramillo, Alvaro, and Peter Burke. New World Blackbirds. Princeton, NJ: Princeton University Press, 1999.

Orians, G. H. Blackbirds of the Americas. Seattle: Washington University Press, 1986.

Bill Freedman

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