Brown-headed Cowbird

Molothrus ater

Summary 4

The Brown-headed Cowbird (Molothrus ater) is named for the male's distinctive brown head, which contrasts with his metallic green-black body. Females are plain brown with lighter heads and streaking on the belly. Brown-headed Cowbirds are nest parasites and lay their eggs in other species' nests.

To hear an example of brown-headed cowbird calls:

Similar SpeciesBrewer's Blackbird Lack the brown head and have a yellow eye.

European Starling Have white spots on the body, with a yellow bill and a dark eye.

Where on campus 5

Brown-headed cowbirds can be seen in the central section of campus. In the Spring, parasitic Brown-headed Cowbird chicks can be seen following Oregon Juncos.

Habitat 5

Brown-headed cowbirds can be found in woodlands, farmland, and suburbs.

LIfe History 5

NestingBrown-headed Cowbirds are well known as "brood parasites", sneaking their eggs into the nests of birds of other species to be reared by adoptive "host" parents (which are often much smaller than them). During the breeding season, Brown-headed Cowbirds tend to engage in courtship and nest parasitism mainly in the morning and to feed in the afternoon. A single female may travel more than 6 km through woodlands to lay as many as several dozen eggs in a breeding season. Providing bird food in spring around the edges of large woodlands unintentionally facilitates brood parasitism by cowbirds, which can greatly reproduce the reproductive output of their hosts. A female will often remove a host egg before adding one of her own. Brown-headed Cowbird eggs have been found in the nests of more than 220 species and over 140 of these are known to have successfully reared young cowbirds. Fed by their host parents, cowbird nestlings develop rapidly, usually leaving the nest after about 10 or 11 days. (EOL)

Feeding seeds and insects (seeds account for around half the diet during the breeding season, but more than 90% in the winter).

Distrubution 5

Brown-Headed Cowbirds are found throughout North America, breeding from British Columbia and southern Quebec in Canada south to southern Mexico.

Migration 5

They are permanent residents in the southern parts of their range; northern birds migrate to the southern United States and Mexico in winter, returning to their summer habitat around March or April.

Sources and Credits

  1. (c) Jerry Oldenettel, some rights reserved (CC BY-NC-SA),
  2. (c), some rights reserved (CC BY-SA),
  3. (c) 116916927065934112165, some rights reserved (CC BY-NC-ND), uploaded by Matt Muir,
  4. Adapted by gillian360 from a work by (c) Unknown, some rights reserved (CC BY),
  5. (c) gillian360, some rights reserved (CC BY-SA)

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