I have a love/hate relationship with cowbirds. I love their shiny feathers and fearless antics, but I know in my heart there is not much to be admired about them except that they eat a lot of insects. In fact it is their eating practices that are responsible for their worst and most infamous habit. Cowbirds literally follow cows and other livestock and eat the insects stirred up by the animals. They will also eat grain in open fields or grassy areas. They often hang out with blackbirds and starlings in large flocks. They don’t have a lot of free time to build a nest or sit around on a nest or care for their young…so they don’t. They let the rest of the bird kingdom raise their young. Yep- every cowbird you see was a foster child, raised by some other species!
Cowbirds aren’t even picky about who raises their young. They will lay their eggs in the nests of bigger birds, smaller birds, birds with different colored eggs. Cowbirds lay more eggs per season than any other wild bird. That means 30-40 eggs! And each one is typically laid in a different nest. Why the other birds don’t automatically reject the intruder egg is a mystery, but most don’t. Only a few of the larger birds will remove the foreign egg.
Cowbirds have all the attributes of the perfect parasite. They scout early in the season and early in the morning so they can easily find unattended nests. They are smart enough to usually remove one host egg and replace it with their own. The cowbirds hatch about one to five days earlier than the host’s chicks, so they get the most attention, and food, from their foster parents. And they are so big that they often crowd out the eggs or new chicks from the nest. If a cowbird happens to lay two eggs in a nest it is almost inevitable that all of the host chicks will die, either from starvation or being knocked out of the nest.
As the number of cowbirds increases in some areas there is a real danger of other species being at risk. Cowbirds are actually trapped and/or killed in some areas containing endangered birds. But apparently it is our logging and agricultural practices that have allowed the cowbird to expand its territory. The more forest we remove and land we expose, the more cattle we own, and the more grain we grow, the more convenient we make life for this bully bird! It seems like a no-win situation.
I just feed the birds each day and enjoy the company of whatever species shows up to eat. I try not to judge…