| Cowbird | |
|---|---|
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| Female brown-headed cowbird | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Passeriformes |
| Family: | Icteridae |
| Genus: | Molothrus Swainson, 1832 |
| Type species | |
| Fringilla pecoris[1] Gmelin, JF, 1789 | |
| Species | |
Cowbirds arebirds belonging to thegenusMolothrus in thefamilyIcteridae. They are ofNew World origin, but some species not native to North America are invasive there, and are obligatebrood parasites, laying their eggs in the nests of other species.
The genus was introduced by English naturalistWilliam Swainson in 1832 with thebrown-headed cowbird (Molothrus ater) as thetype species.[2][3] The genus name combines theAncient Greekmōlos, meaning "struggle" or "battle", withthrōskō, meaning "to sire" or "to impregnate".[4] The English name "cowbird", first recorded in 1839, refers to this species often being seen near cattle.[5]
The genus contains six species:[6]
| Common name | Scientific name and subspecies | Range | Size and ecology | IUCN status and estimated population |
|---|---|---|---|---|
| Screaming cowbird
| Molothrus rufoaxillaris Cassin, 1866 | Northeast and central Argentina, southeast Bolivia, central Brazil and throughout Paraguay and Uruguay | Size: Habitat: Diet: | LC |
| Giant cowbird
| Molothrus oryzivorus (Gmelin, JF, 1788) Two subspecies
| Southern Mexico south to northern Argentina, and on Trinidad and Tobago | Size: Habitat: Diet: | LC |
| Shiny cowbird
| Molothrus bonariensis (Gmelin, JF, 1789) | South America, the Caribbean, and Florida | Size: Habitat: Diet: | LC |
| Bronzed cowbird
| Molothrus aeneus (Wagler, 1829) | Southern U.S. states of California, Arizona, New Mexico, Texas, and Louisiana south through Central America to Panama | Size: Habitat: Diet: | LC |
| Bronze-brown cowbird | Molothrus armenti (Cabanis, 1851) | Colombia | Size: Habitat: Diet: | NT |
| Brown-headed cowbird
| Molothrus ater (Boddaert, 1783) Three subspecies
| Southern Canada, United States, and Mexico | Size: Habitat: Diet: | LC |
Oneextinct species,Molothrus resinosus, is known fromfossil remains recovered from theTalara Tar Seeps of northwesternPeru, and likely went extinct during thelate Quaternary. It may have been a close associate ofPleistocene megafauna communities, and may have gone extinct following their collapse in populations.[7] Theconvex-billed cowbird (Pandanaris convexa) is another extinct species that likely co-evolved with the megafauna, though it is placed in its own genus.
The nonparasiticbaywings were formerly placed in this genus; they are now classified asAgelaioides.
Cowbirds eat mostly insects and seeds. Some species followungulates to catch insects stirred up by the larger animals' grazing.
Cowbirds reproduce by laying their eggs in other birds' nests. Female cowbirds observe a potential host bird laying its eggs, and when the nest is left momentarily unattended, the cowbird lays its own egg in it. The female cowbird may continue to observe this nest after laying eggs. Some bird species have evolved the ability to detect such parasitic eggs, and may reject them by pushing them out of their nests, but female cowbirds have been observed to attack and destroy the remaining eggs of such birds in retaliation, as suggested by theMafia hypothesis.[8]
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