Image # 7063
adult male display sky pointing Sky-pointing display by adult male Brown-headed Cowbird at Middle Creek Wildlife Management Area in Pennsylvania. Originally called Buffalo birds, Brown-headed Cowbirds are obligate brood parasites. This means the female cowbird invariably lays her eggs in the nest of another species. Worse, when the young cowbird hatches, it pushs out all the other eggs and/or nestlings. Open country birds have learned to deal with cowbirdsevolved tSo the As humans have fragmented habitats with clearings and suburbs, the cowbirds have been given greater access to more and more forest birds' nests. The populations of forest birds - which have not evolved strategies to deal with lsMany of these birds have never evolved strategies to deal with such enforced adoptionsthis theft of services and their populations have been adversely affected. Many open country birds will renest elsewhere or build a new nest over the cowbird egg and will lay a new brood in the new nest. This building war can go up several levels in one year if the cowbird is persistent.
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