Brown-Headed Cowbird

From Ohio History Central


Scientific Name: Molothrus ater
Habitat: fields, barnyards, roadsides, wood edges, and river groves
Adult Weight: 1.5 - 2 oz.
Adult Body Length: 7 inches
Nesting Period: April through June
Clutch Size: Lays one egg almost every day of nesting period.
Foods: Insects, seeds, small fruit, and waste grain


The brown-headed cowbird is one of the most hated native songbirds. The females are brood parasites. This means that rather than building a nest and incubating their own eggs, they will lay an egg, almost daily, in the nests of other songbirds. The cowbirds generally hatch first and are larger and more aggressive than the nestlings that are supposed to be there. As a result, these young quickly die of starvation and populations of approximately 150 species of songbirds such as vireos, warblers, buntings and sparrows have declined.


19th Century

Cowbirds expanded their range from the Great Plains into Ohio in 1840. By the late 1800s, they had quickly spread across the state as summer residents.

20th Century

Populations remained stable through the 1930s and began to increase in the 1950s and 60s. It was not until 1940 that cowbirds began to spend the winter in Ohio. By the 1950s and 60s, large numbers could be found during the winter months. An estimated 40,000 were seen roosting in Delaware County in 1953-54. The average winter roost contains 500-5,000 cowbirds.

Today there are programs to control cowbird populations in hopes of increasing the populations of other native songbirds.

See Also


  1. Peterjohn, John. The Birds of Ohio; Indiana University Press, Bloomington, IN; 1989.