page_title: Brown-headed cowbird
section_title: Breeding
hierarchical_section_title: Brown-headed cowbird / Behavior and ecology / Breeding
caption_attribution_description: English: Eastern Phoebe (Sayornis phoebe) nest with one Brown-headed Cowbird (Molothrus ater) egg
context_page_description: The brown-headed cowbird is a small obligate brood parasitic icterid native to temperate and subtropical North America. 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.
context_section_description: The brown-headed cowbird is an obligate brood parasite: it lays its eggs in the nests of other small passerines (perching birds), particularly those that build cup-like nests. The brown-headed cowbird eggs have been documented in nests of at least 220 host species, including hummingbirds and raptors. The young cowbird is fed by the host parents at the expense of their own young. Brown-headed cowbird females can lay 36 eggs in a season. More than 140 different species of birds are known to have raised young cowbirds.
  Unlike the common cuckoo, the brown-headed cowbird is not divided into gentes whose eggs imitate those of a particular host.
  Some host species, such as the house finch, feed their young a vegetarian diet. This is unsuitable for young brown-headed cowbirds, meaning almost none survive to fledge.
caption: Eastern phoebe nest with one brown-headed cowbird egg
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