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Cowbird
Female brown-headed cowbird
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Passeriformes
Family:	Icteridae
Genus:	Molothrus Swainson, 1832
Type species
Fringilla pecoris Gmelin, JF, 1789
Species
M. rufoaxillaris M. oryzivorus M. bonariensis M. aeneus M. armenti M. ater

Cowbirds are birds belonging to the genus Molothrus in the family Icteridae. They are of New World origin, but some species not native to North America are invasive there, and are obligate brood parasites, laying their eggs in the nests of other species.

The genus was introduced by English naturalist William Swainson in 1832 with the brown-headed cowbird (Molothrus ater) as the type species. The genus name combines the Ancient Greek mōlos, meaning "struggle" or "battle", with thrōskō, meaning "to sire" or "to impregnate". The English name "cowbird", first recorded in 1839, refers to this species often being seen near cattle.

Species

The genus contains six species:

Genus Molothrus – Swainson, 1832 – six species

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 M. o. impacifus (Peters, JL, 1929) M. o. oryzivorus (Gmelin, JF, 1788)	Southern Mexico south to northern Argentina, and on Trinidad and Tobago	Size: Habitat: Diet:	LC
Shiny cowbird Male Female	Molothrus bonariensis (Gmelin, JF, 1789) Seven subspecies M. b. minimus Dalmas, 1900 M. b. cabanisii Cassin, 1866 M. b. venezuelensis Stone, 1891 M. b. aequatorialis Chapman, 1915 M. b. occidentalis Berlepsch & Stolzmann, 1892 M. b. riparius Griscom & Greenway, 1937 M. b. bonariensis (Gmelin, JF, 1789)	South America, the Caribbean, and Florida	Size: Habitat: Diet:	LC
Bronzed cowbird	Molothrus aeneus (Wagler, 1829) Three subspecies M. a. loyei Parkes & Blake, 1965 M. a. assimilis (Nelson, 1900) M. a. 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 Male Female	Molothrus ater (Boddaert, 1783) Three subspecies M. a. artemisiae Grinnell, 1909 M. a. obscurus (Gmelin, JF, 1789) M. a. ater (Boddaert, 1783)	Southern Canada, United States, and Mexico	Size: Habitat: Diet:	LC

One extinct species, Molothrus resinosus, is known from fossil remains recovered from the Talara Tar Seeps of northwestern Peru, and likely went extinct during the late Quaternary. It may have been a close associate of Pleistocene megafauna communities, and may have gone extinct following their collapse in populations. The convex-billed cowbird (Pandanaris convexa) is another extinct species that likely co-evolved with the megafauna, though it is placed in its own genus.

The nonparasitic baywings were formerly placed in this genus; they are now classified as Agelaioides.

Behavior

Cowbirds eat mostly insects and seeds. Some species follow ungulates to catch insects stirred up by the larger animals' grazing.

The birds in this genus are infamous for laying their eggs in other birds' nests. The female cowbird notes when a potential host bird lays 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 the female cowbird has been observed to attack and destroy the remaining eggs of such birds as a consequence, dissuading further removals. Widespread predatory behaviors in cowbirds could slow the evolution of rejection behaviors and further threaten populations of some of the greater than 100 species of regular cowbird hosts, favoring host acceptance of parasitic eggs in a mafia-like contest between cowbirds and other species.

References

1. "Icteridae". aviansystematics.org. The Trust for Avian Systematics. Retrieved 2023-07-16.
2. Swainson, William John; Richardson, J. (1831). Fauna boreali-americana, or, The zoology of the northern parts of British America. Vol. Part 2. The Birds. London: J. Murray. p. 277. The title page bears the year 1831 but the volume did not appear until 1832.
3. Paynter, Raymond A. Jr, ed. (1968). Check-list of Birds of the World. Vol. 14. Cambridge, Massachusetts: Museum of Comparative Zoology. p. 195.
4. Jobling, James A. (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. p. 258. ISBN 978-1-4081-2501-4.
5. "Cowbird". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
6. Gill, F.; Donsker, D.; Rasmussen, P. (July 2020). "IOC World Bird List (v 10.2)". Retrieved July 15, 2020.
7. Steadman, David W.; Oswald, Jessica A. (July 2020). "New species of troupial (Icterus) and cowbird (Molothrus) from ice-age Peru". The Wilson Journal of Ornithology. 132 (1): 91–103. doi:10.1676/1559-4491-132.1.91. S2CID 220714575.
8. Jeffrey P. Hoover; Scott K. Robinson (13 March 2007). "Retaliatory mafia behavior by a parasitic cowbird favors host acceptance of parasitic eggs". Proceedings of the National Academy of Sciences. Retrieved 26 August 2009.

Further reading

• Jaramillo and Burke, New World Blackbirds ISBN 0-7136-4333-1

External links

• Audubon Society: Cowbirds and Conservation

• Brood parasites
• Cowbirds
• Birds of North America
• Bird genera
• Taxa named by William John Swainson