The Cowbird Conundrum

My head cold is starting to subside. Non Birding Bill and I are hangin' at Mr. Neil's this weekend to keep an eye on the newly installed bees and to prep for banding on Sunday. The rain is making for some interesting feeder watching. Outside the kitchen window I can see a pine warbler and a black and white warbler going for the suet feeder. On the one hand this is exciting to see. On the other hand, I know these insect eating birds are desperate on their migration if they are eating peanut butter suet.

Thanks to a note left by Minnesota BirdNerd in the comments, my mind has been totally blown by the brown-headed cowbird theory. For years many of us have spouted the reasonable sounding defense of the brown-headed cowbird: they followed herds of bison on the prairie in North America, eating insects that were kicked up and evolved over time to deposit their eggs in the nests of other birds since their traveling lifestyle meant that they couldn't stay in one place long enough to build a nest, incubate eggs, and raise young. However, nomadic herds of bison are no longer in existence, brown-headed cowbirds follow sedentary humans and wreak havoc on nesting birds.

However, Alvaro Jaramillo who wrote the book about blackbirds (literally, he wrote the book on blackbirds) has this theory:

"This cannot be true. If you look at the evolution of the cowbirds (the entire genus Molothrus) you will find that they most likely arose in South America where there are no bison. As well, the Shiny Cowbird and Brown-headed Cowbird appear (based on the phylogeny developed by studying variations in mitochondrial DNA sequence) to be the most recently derived species in the cowbird clan. Thus, by the time that the Brown-headed Cowbird arose as a species it was already part of a lineage of brood parasitic birds, it was not the first. Cowbirds were 'pre-adapted' to a nomadic lifestyle due to their brood parasitism, but this behavior did not evolve due to a 'need' to follow Bison."

So, what does this mean? Are cowbirds just downright evil? No, they are just trying to find their way in this world like the rest of us. Although, now I have to think back to all the articles I've written and my already-at-the-printer-book City Birds Country Birds that has the bison theory in it. Sigh. Curse you brown-headed cowbirds and everything you stand for!