Brown-headed Cowbird

Molothrus ater

  • Authors: Lowther, Peter E.
  • Published: Jan 1, 1993

Free Introduction Article Access

The Introduction Article is just the first of 11 articles in each species account that provide life history information for the species. The remaining articles provide detailed information regarding distribution, migration, habitat, diet, sounds, behavior, breeding, current population status and conservation. Each species account also includes a multimedia section that displays the latest photos, audio selections and videos from Macaulay Library’s extensive galleries. Written and continually updated by acknowledged experts on each species, Birds of North America accounts include a comprehensive bibliography of published research on the species.

A subscription is needed to access the remaining account articles and multimedia content. Rates start at $5 USD for 30 days of complete access.

Subscribe Now

Already a subscriber? Sign In
Figure 1. Distribution of the Brown-headed Cowbird.
Brown-headed Cowbird,adult male.

May; NY State.; photographer Marie Reed

The Brown-headed Cowbird, North America's best known brood parasite, lays its eggs in the nests of many different species. Originally these "Buffalo Birds" were limited to short-grass plains, where they followed herds of buffalo (Bison bison) and fed on the insects stirred up by their movement. This cowbird has since dispersed widely as European settlement opened forests and homogenized the environment into the agricultural and suburban landscapes of today. Cowbird expansion has exposed naive populations and new species to brood parasitism, and the pressure on such host populations can be substantial. Female cowbirds wander widely, overlap their breeding ranges, and may lay 40 eggs per season.

Cowbirds are difficult to study because their breeding activities are distributed among many host nests. Herbert Friedmann's monograph (Friedmann 1929) provides a beginning to the vast and sometimes conflicting literature on the Brown-headed Cowbird (see also Friedmann 1963, Friedmann et al. 1977, Friedmann and Kiff 1985). Life history studies of host species also give information on cowbird biology and host-cowbird interactions; see especially studies of Prairie Warblers (Dendroica discolor; Nolan and Thompson 1978), Kirtland's Warbler (Dendroica kirtlandii; Mayfield 1960, Walkinshaw 1983), Ovenbird (Seiurus aurocapilla; Hann 1937) and Song Sparrows (Melospiza melodia; Nice 1937). Besides Kirtland's Warblers, other endangered or threatened species are also "good" hosts, so management concerns require a full understanding of cowbird biology.

Recommended Citation

Lowther, Peter E. 1993. Brown-headed Cowbird (Molothrus ater), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.