The Oft Maligned Cowbird

By Sarah W.

 The cowbird is one of the early birds to show up en masse in our area. You know that Spring egg-laying season is immanent when you start seeing these birds. What’s the connection? It is parasitism, because the cowbird does not construct a nest, but lays her eggs in the nests of other species.

How did this come about? In the past, cowbirds would obtain their food by following the buffalo herds. They picked ticks and parasites off the buffalo, hopping along behind them scarfing up the insects and seeds stirred up by their hooves as they moved over the plains. This was not conducive to incubating and feeding nestlings. The evolutionary solution was to have another bird raise their young.

 We know what happened to the buffalo. As a result, the cowbirds probably began following domestic cattle and the plow thus continuing their “free and easy lifestyle,” laying eggs in many species’ nests. (When I was a farmer, cowbirds would sometimes follow after me as I rototilled, unbothered by this noisy critter that churned up food for them.)

Sometimes a songbird will build over the cowbird eggs to smother them. Occasionally one is able to toss the foreign egg out of the nest. But many cowbird eggs do hatch and are raised by the “foster” parents. (I am trying not to be too upset at this – I tell myself that it’s evolution.) Songbirds have many more human-caused perils that are diminishing their numbers.If you have ground feeding yard birds, see if you can pick out the cowbirds. The male is sleek and shiny with a brown head and black body. The female is a nondescript brown-camouflaged well to slip onto a nest, lay her egg and be gone.

 If you have ground feeding yard birds, try to pick out the cowbirds. Let us know if you see them (and send us photos)! The male is sleek and shiny with a brown head and black body. The female is a nondescript brown–the perfect camouflage to slip onto a nest, lay her egg and be gone.

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