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Brown-headed cowbirds are close relatives of the orioles and blackbirds. They are notorious and highly successful brood parasites, laying their eggs in various host species, usually songbirds. The cowbird chicks are raised by the unwitting host, often at some cost to the survival of the host chicks (baby cowbirds are large, greedy, and grow fast). Over a hundred host species have been recorded and a single female cowbird can lay eggs in 20 or 30 nests in one season. Unsurprisingly, they can be a serious impediment to the recovery of endangered songbirds; in southern California, one of these is the least Bell's vireo. This male (females are dull, streaky brown, below) was photographed on a bitterbrush along Convict Creek, Mono County, California. |
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