Cowbird
Cowbirds are birds belonging to the genus Molothrus in the family Icteridae. They are of New World origin. They are brood parasites, laying their eggs in the nests of other species.
The genus was introduced by the English naturalist William John Swainson in 1832 with the brown-headed cowbird 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 genus contains six species:
| Image | Scientific name | Common Name | Distribution |
| Molothrus rufoaxillaris | Screaming cowbird | north east and central Argentina, south east Bolivia, central Brazil and throughout Paraguay and Uruguay | |
| Molothrus oryzivorus | Giant cowbird | southern Mexico south to northern Argentina, and on Trinidad and Tobago | |
| Molothrus aeneus | Bronzed cowbird | southern U.S. states of California, Arizona, New Mexico, Texas, and Louisiana south through Central America to Panama | |
| Molothrus bonariensis | Shiny cowbird | South America | |
| Molothrus ater | Brown-headed cowbird | Southwestern Canada, United States and Mexico |
The non-brood parasitic baywings were formerly placed in this genus; they are now classified as Agelaioides.
Behavior
Cowbirds are insectivores.The birds in this genus are infamous for laying their eggs in other birds' nests. The female cowbird will note when a potential host bird lays its eggs, and when the nest is left momentarily unattended, the cowbird will lay its own egg. 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. However, 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.