Friday, September 04, 2009
It's always a pleasure to watch the cowbirds as they pick for bugs and seed heads in wool, even as the wool remains on the sheep. Most of the sheep don't mind their presence at all, and the birds fly/hop from the back of one sheep to another. The fattest brown-headed cowbirds I've ever seen stayed in our corral one winter as we grain-fed some calves.
Cowbirds are parasitic birds, laying their eggs in the nests of a wide range of other species. They apparently never raise their own young. A female may lay up to about 40 eggs per year, but only three percent end up as adults. The female monitors the nests she parasitizes, and may destroy the nests of host birds that won't care for her young.
Cowbirds were originally a bison-following bird of the Great Plains, but are now often seen foraging on the ground in agricultural areas for seed, most often in association with grazing animals.