Monday, April 26, 2010


"Cowbirds are brood parasites, laying their eggs in the nests of other birds and leaving them to the care of foster parents. Unlike parasitic Old World cuckoos, which lay eggs closely resembling those of a host species, cowbirds lay eggs in the nests of more than 200 other species, mostly smaller than themselves. Some host species eject the unwanted egg, others lay down a new nest lining over it, but most rear the young cowbird as one of their own. The young cowbird grows quickly at the expense of the young of the host, pushing them out of the nest or taking most of the food. It has been suggested that cowbirds became parasitic because they followed roving herds of bison and had no time to stop to nest."

- Audubon Field Guide,
North American Birds

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