If you looked at the cowbird video I wrote about a few days ago you saw the female cowbird pluck and toss to the ground an entire nestful of newly hatched warblers. The cowbird most likely then laid an egg in the nest. She was acting to help ensure that the female warbler would invest her entire energies in hatching the cowbird egg and raising the cowbird hatchling. Cowbirds have evolved to depend upon other bird species in this way. Most often, the cowbird simply lays an egg in the nest to be hatched along with the host-species eggs. Killing the young birds of the host species is an extreme in cowbird survival behavior. Is the cowbird a ‘bad’ bird for doing this? How did you feel when you watched the video? It was hard for me to accept without emotion that this is a natural behavior.

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