Hey guys welcome back! Over the course of this blog, we have come across a few invasive species, some of which are responsible for the declining populations of native birds. Today’s bird is not invasive, technically, since it is native. However, the brown-headed cowbird is considered by many to be a nuisance bird. They are North America’s most prolific brood parasite. I mentioned the term in my last post, but I’ll expand on it here, since it’s closely related to today’s bird, and also for those of you that may be unfamiliar with the term. Brown-headed cowbirds are brood parasites in the blackbird family. What this means is, they don’t build nests, but rather lay their eggs in the nests of other bird species. Those baby cowbirds are then raised by their new foster parents. Although some species do recognize the foreign eggs and discard them, most species don’t and unknowingly raise cowbird chicks.
The interested thing is how cowbirds know how to be cowbirds despite being raised by other species. It’s weird when you stop and think about it. How can a bird raised as a warbler or bunting know how to be a cowbird? Scientists are still figuring it out. There’s a good article about it here.
Brown-headed cowbirds are common throughout the U.S., Mexico, and southern Canada. During the fall and winter, they can often be found in mixed blackbird flocks foraging on the ground. The males are a glossy black, with a brown head, and the females are plain brown. Few birds have given me as much ID issues as female/juvenile brown-headed cowbirds. They are just so plain looking, and I’m always like “what the hell is this bird that has no distinguishing marks?” I usually figure it out pretty quick, but they still give me pause to this day. In fact just a few weeks ago I came across a juvenile cowbird. And at first I was like “what is that?” Then I saw an adult song sparrow feeding it. I thought to myself oh it must just be a young song sparrow that hasn’t gotten its stripes. Nope. Later when I was putting my pics into the photo ID on the Merlin app (I do this sometimes just to test how accurate the photo ID is) it came back as a cowbird. I felt kind of stupid because of course that’s what it was. It was the first time I saw a young cowbird being fed by the adult of another species though, so that was pretty cool! Check back next time when we get to a shorebird that isn’t always found near the shore: the killdeer. See you all then!
Side note: I just moved back to the Cleveland area! My time living and birding in St. Louis was a great transitionary period for me but it was time to come home and I’m looking forward to getting out and birding more often (and just in time for shorebird season!)