Know Your Icterids, Part Three: Brown-headed Cowbird

After Red-winged Blackbirds, Brown-headed Cowbirds are probably the most commonly seen birds in the birdcam; they’re pretty much always around. As with other icterids, the males and females are quite different. Males are black with a distinctive brown head, while females, which are similar in shape but just a tad smaller, are tan with few distinct markings.

I took these three cowbird shots this morning because I thought it was interesting how the male toward the top of the frame was posturing; he did this several times. (The male at the bottom of the frame shows a more-typical cowbird posture.) The female, too, seemed to be acting unusual, crouching down the way you see in these images. I wondered if this was courtship behavior, but no actual mating took place that I noticed.

Brown-headed Cowbirds are nest parasites, as most readers of this blog probably already know. They don’t build a nest or rear their own young; instead, the female lays an egg in the nest of some other perching bird. I’ve read that as it matures, the young cowbird will often grow larger and faster than its nestmates, pushing them out of the nest to monopolize the attentions of its foster parents.

The Wikipedia article on the Brown-headed Cowbird currently includes the following photo, taken by Frankie Rose, showing a Brown-headed Cowbird egg in the nest of an Eastern Phoebe:

According to that Wikipedia article, the cowbird’s nest parasitism evolved as an adaptation to the bird’s traditional lifestyle following the North American bison herds. With the arrival of European settlers and their livestock, they found themselves admirably adapted to the new conditions, and have continued quite successfully (in the eyes of some, a little too successfully) to this day.

One Response to “Know Your Icterids, Part Three: Brown-headed Cowbird”

  1. Rafa says:

    Great articles about icteridae, Elanus. Thanks a lot for all the info. Keep up the good work!!

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