Brown-headed Cowbird (Molothrus ater)


I saw this male at Burnaby Lake, my second time seeing these cowbirds after seeing some at Reifel a few days earlier. These birds are brood parasites; they do not build nests. Instead, the female finds a nest, usually belonging to a smaller species, and lays her eggs there. A few species recognize the cowbird eggs and dispose of them. But most species do not differentiate them and even feed the juvenile cowbirds. I learned about Brown-headed Cowbird behaviour from All About Birds. There is even a picture of a Common Yellowthroat adult feeding a much larger Brown-headed Cowbird juvenile.


    • Yes, it is quite brown. The initial photo had overly turquoise water so I browned it a bit :-). You’ve made me curious… I will play around with a monochromatic version.


  1. I try not to play favorites with creatures, but this is one I really don’t like because in our area it can really get too numerous. If they would parasitize the blasted English House Sparrows I would rejoice! 🙂

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    • Hmm. I read a bit about some areas trying to reduce brown-headed cowbird populations to try to boost populations of some endangered warblers whose nests are parasitized by these cowbirds. But I don’t know much about this issue and at first glance, their numbers seemed reasonable in the two places I saw them near Vancouver (but I haven’t done any research about their impact in those areas). I did start reading an article called Brown-Headed Cowbird Villain or Scapegoat yesterday. At the moment, I’m inclined to think that cowbirds are only an issue because of habitat loss caused by humans. But I should finish the article to get more information :-). What kinds of problems do cowbirds cause in your area? I just moved back to Calgary and I wish the magpies would turn the volume down on their afternoon shrieking. At least I don’t hear them in the mornings or most of the day, and they are pretty to look at :-).


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