Sunday, May 23, 2010

Brown-headed Cowbird

This female Brown-headed Cowbird is a obligate brood parasite, which means that she always lays her eggs in other species' nests.  Cowbirds do not build their own nests. They parasitize over 220 host species, ranging from kinglets to meadowlarks.  Yellow Warblers and Song Sparrows are particularly vulnerable to cowbirds.  Rare species, such as Kirtland's Warblers, are also adversely impacted by cowbird parasitism. Female cowbirds range widely and lay as many as 40 eggs per season. I do not know how young cowbirds learn how to sing and act like cowbirds instead of their host species. My cowbird information is gleaned from Lowther (1993).

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