Cowbird behavior

[Birdzilla]

The Brown-headed Cowbird is a brood parasite. It lays its eggs in the nests of other species, often in the nest of a much smaller bird such as a warbler. Historically cowbirds followed the heards of grazing bison, feeding on the insects the bison stirred up. In order to keep up with the bison, they would lay eggs in the nests of other birds and so they could keep following their food source.

Cattle and lawn mowers have replaced the bison and the cowbird no longer has to follow such a migratory life style and interesting behaviors are being observed.

One recent study indicates that the female cowbird will monitor the nests in which she has laid an egg. If the host species has thrown the cowbird egg out of the nest, the female cowbird will destroy the nest and eggs of the host species. If the host rebuilds the nest and starts to lay eggs again, the female cowbird will time her egg production to match the host species and will again lay her egg in the host nest.