Brown Headed Cowbird: Nature's Welfare Bum

This time of year every morning I'm filled with anticipation, wondering if another bird species is going to arrive today. Lately, I've been disappointed more often than not. So while I'm waiting for the next species to arrive and remind me it's spring, I think I'll talk about the Brown-headed Cowbird, nature's welfare bum.

This bird's call is beautiful. It's very high-pitched. Sometimes the pitch is so high it's almost inaudible. It's hard to describe--it sounds like water in a tumbling brook running over rocks (except that the pitch is many times higher).

Although this picture doesn't do the bird justice, it really is gorgeous. Its head is brown and its body is black, but it also has metallic purple or green highlights that change color depending on how sunlight is hitting it.

But don't be fooled. This bird is an insidious, destructive baby killer. It sneaks into other birds' nests when they're not looking, destroys their eggs and lays its own. The bird that made the nest ends up having to raise the cowbird chicks, who usually grow faster than their legitimate "siblings." Baby cowbirds out-compete their step-siblings, frequently taking more than their share. This increases the risk that the legitimate chicks will not make it to adulthood. Some birds can recognize their eggs and throw them out of the nest. Other birds will leave the area to nest elsewhere when they find their nest has been invaded. But the cowbird is moving into new territory occupied by species that haven't evolved any defense. In these cases, native species can be decimated in just a few years.

The picture above is of the male of this species. The female is a gray-brown, and looks exactly like a female Brewer's blackbird.  They seem to take advantage of this similarity. If blackbirds and cowbirds are in the same area, they can usually be found together in the same flock. In my area, I'm pretty sure that the bulk of the cowbird young are raised by blackbirds.

You can protect your local populations. I've noticed that this bird is not just lazy when it comes to raising children. It's not much of a forager, either.  If you buy birdseed from the store, stop doing it. Most wild bird seed contains millet. Most birds don't like millet. But cowbirds do.  Research the bird species that visit your yard. If you want to feed them, find out what they eat. Purchase that specific type of food. Don't buy anything with the words "wild" and "bird seed" in the title. It's too generic, and will help birds like this gain a foothold. Also, when feeding birds, less is better. Put out only the amount of food that will be eaten in a few minutes. Make sure that the birds are hungry enough to eat whatever falls on the ground, too. Your feeder is not the only source of sustenance for your friends, and if they're leaving food behind they're probably eating more than is healthy anyway.

Your second line of defense is quail eggs. On the day after Easter, go to Walgreen's and buy 5 or 6 Easter egg baskets. Get some straw from the local feed store or dried grass from your lawn, and make nests. Try to put the nests in places that are easy for you to access but seem natural.  Don't underestimate cowbirds' powers of observation: The best time to work around these fake nests is during the night when birds are sleeping. Take a magic marker and make a tiny mark on each quail egg, to be sure you can identify when cowbirds are using your nest. Every other day, put one quail egg in each nest. Just one. Do this until the nests have accumulated 4-5 eggs.

Every day, visit the nests. Move eggs when you do, because that's what the mother bird would do. Quail eggs will start to go bad after a week, so replace quail eggs with fresh ones weekly. If you discover cowbird eggs, mark them and leave them there for a week or so (like the quail eggs, remove them before they go bad). If the cowbird finds out the "mother bird" has discovered her deception, she'll quit using that nest.

I would imagine that after a few years, local bird populations will begin to develop resistance to cowbirds. Perhaps they'll learn to recognize the interlopers' eggs. Or once the baby cowbirds hatch, they'll learn to recognize them and throw them out of their nest. I don't know for sure, because I've only been dealing with them for a few years. But I do know that, though cowbirds are native to North America, their range is growing as they come into contact with humans who like to feed birds. And they are a non-native, invasive species to much of the territory they now occupy. They can have a devastating impact on the species in your neighborhood.

As soon as the cowbirds show up at my house, I'll post some pictures of my stealth nests. I don't expect them here until the beginning of May. I'd like to hear from you about your cowbird woes and any successes you experience. So post a comment, or send me an email.