There are many different bird species in North America that are revered for their beauty and personality. However, there are also those that are reviled. Many of these species are non-native and have a habit of taking over areas previously inhabited by native birds. There is one native species however, that was here all along, and wasn’t a big problem until humans made it so.
This is the Brown-headed Cowbird. At first glance they look like any other bird. Males have a namesake brown head and a glossy black body and females are covered entirely in a light grayish brown color. These birds thrive in open areas such as fields, cattle pastures, agricultural farms and backyards. In fact, most backyard bird watchers are probably quite familiar with the species.
If Brown-headed Cowbirds aren’t non-native then what’s the problem with these familiar birds? It all has to do with the way they raise their young, or rather don’t raise their young. Brown-headed Cowbirds are brood parasites, meaning they lay their eggs in the nests of other birds leaving their young to be raised by a completely different species. The surrogate parents are unaware that their nest has been parasitized by the cowbird and raise the cowbird as their own. While this may sound like a sweet story of adoption and acceptance, it most certainly is not. Cowbirds hatch faster than most other bird species and also grow at a faster rate, meaning they easily outcompete their nestmates. Sometimes cowbirds will even push eggs and nestlings of other species out of the nest to ensure their greatest chance for survival.
While this certainly seems mean, it’s an adaptation that actually makes a lot of sense given the cowbirds lifestyle. It’s believed that Brown-headed Cowbirds used to follow herds of bison as they moved across the great plains of the United States, eating insects that also followed the herd or got kicked up from the grass by the large animals. This more nomadic lifestyle meant that they couldn’t stay in one place to make a nest and raise young, thus brood parasitism became the norm for the species.
Brown-headed Cowbirds can still be seen following Buffalo and Cattle across the plains, but now their range has expanded both east and west to the point where it now engulfs the entirety of the lower 48 states, Southern Canada, and a large portion of Mexico. Much of this expansion was actually a side effect of humans expanding. Since Cowbirds like open areas such as fields and lawns, the more farms and homes that popped up, the more habitat was made for cowbirds to thrive. Another way in which humans accidentally aided the brown headed cowbird was by offering them seeds. This was partially due to agricultural practices leaving seed crops in fields, and partially due to the rise of backyard bird feeding. With a more than adequate amount of seeds to supply Cowbirds with sustenance coupled with their preferred habitat, the species no longer needed to follow bison and other large animals across the country. However, their habit of laying their eggs in the nests of other birds remained.
What started as a necessary adaptation has turned into something of an ecological disaster as Brown headed Cowbirds reside in the same place for the duration of the breeding season, wreaking havoc on nearby breeding birds. They have proved detrimental to many different species, most notably the endangered Black-capped Vireo and Kirtlands Warbler. This has become such a problem in areas such as the jack pines that the Kirtlands warblers breed in, that efforts have begun catching and removing combirds to prevent them from destroying broods of the endangered warblers.
While cowbirds are most detrimental to at-risk species, they are a nuisance to almost all birds in areas they inhabit as over 200 different species of birds have been found to have nests parasitized by brown headed cowbirds.
All of this has led to backyard bird lovers and ecologists despising the Brown-headed Cowbird, but can we really blame them? After all it was humans that changed the landscape so much that it actually altered the lifestyle of the species entirely.
Nonetheless, Brown-headed Cowbirds pose a unique problem for other birds as well as the humans that care about them. Since they are a native bird, it is illegal to kill them, and removing cowbird eggs from nests is said to sometimes be met with retribution by the cowbird mother. Some types of birds recognize the cowbird eggs and abandon the nest, or destroy the foreign egg. Most however, can’t spot the difference and end up raising a cowbird that directly or indirectly destroys the original brood.
So what can be done about the Brown-headed Cowbird and the destruction they bring upon other bird species? In some places where sensitive species are nesting, efforts to catch and remove cowbirds are in effect. Other than that, there isn’t much that can be done. It looks like for the foreseeable future, brown headed Cowbirds will be a part of life for birds, and backyard bird watchers across the country.
At their core, these birds are just doing what it takes to pass on their genes, ensuring that the species will endure the test of time. They are birds that developed an ingenious adaptation, that has now been rendered unnecessary by the development of human civilization and yet still it persists. Sure, many people love to hate them, but the Brown headed Cowbird is here to stay, and we’re all just going to have to learn to live with them.
If you liked this video leave us a like and a comment. Also, check out our video on how the House Sparrow spread across North America. Thanks for watching, we’ll see you next time, on Badgerland Birding.
