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Cowbird Eggs

Dear Bird Folks,

For the past few years a pair of House Finches have nested in the hanging plant on my front porch. Yesterday, while I was watering the plant, I noticed four small finch eggs and one large speckled egg. I assume the large egg belongs to a cowbird. Is the cowbird egg going to hatch and become a problem for the young finches? Should I remove the egg or let nature take its course?

-Susan, Yarmouth Port


Fun Question Susan,

The other day I saw a book in a book store, of all places. I can’t remember the exact title, but the book was nothing more than a series of questions. The book didn’t provide any answers, it simply asked questions, and it was up to us to formulate our own answers. Many of the questions had a moral twist to them. There was stuff like, “Would you return a lost wallet?” and “Would you take home a lost dog?” and “If a guy ran in front of your car, would you slam on the brakes, even if he was wearing a Yankee hat?”

These questions and your cowbird question present us with a dilemma. (Also pronounced “delimmer” in some parts of Massachusetts. Don’t ask me to explain.) If that cowbird egg hatches, a family of baby House Finches could be doomed to starvation. If the egg is removed, then the cowbird may not have any offspring this year. It’s a tough call and I’m not sure if I can provide the answer you are looking for. Perhaps, with a little information about both birds, you can make your own decision.

For those of you who don’t know already, cowbirds are parasitic nesters. They don’t build their own nests. It is believed that cowbirds used to follow the moving bison herds so they didn’t have time to build a nest, incubate eggs and raise their young before the herd moved on. Cowbirds would simply drop an egg into another bird’s nest and continue with the herd. The “host” bird is often tricked into raising the baby cowbird, feeding it, teaching it to fly, and paying for college, which is a sweet deal for the parent cowbirds.

The downside is that often the “host” birds aren’t able to feed both the fast growing cowbird and their own less aggressive babies. Thus their own nestlings may starve to death while the young cowbird thrives. Sounds pretty evil eh? Why wouldn’t we want to toss out the cowbird’s egg and let the baby House Finches live? Well, if we do a background check on House Finches, we find that they too have their own baggage and are far from the perfect avian citizens.

House Finches are birds from western North America. They were illegally introduced to this part of the country back in the 1940’s. Since then their population has exploded. Taking advantage of our many bird feeders, hanging plants, and the fact that life is so much better on the east coast than the west, the House Finch has become ubiquitous.

What’s so bad about that you ask? Well, usually when one bird moves into an area, other birds are forced out. In recent years the population of the similar and locally native Purple Finch has been dropping. Some experts feel that the rapidly expanding House Finch population is to blame. Plus, the fast breeding House Finch population has become plagued with conjunctivitis, a deadly eye disease, that it may be passing on to other birds. Now who’s the bad bird?

Both birds have issues. The cowbird raises havoc with other nesting songbirds, while the regionally introduced House Finch has also caused its share of problems. Do you dump the egg and save the baby finches or do let the egg hatch and allow more parasitic cowbirds into the world? Tough question, eh? Should we poll the audience? What would you people playing along at home do? Thumbs up or down on the cowbird egg? I can’t say for sure, but I’d be willing to bet that most people would say to dump the egg. Heck, we know what’s better for nature and as soon as nature learns that, the better off it will be.

Oh, there’s one more piece of information that I need to tell you about. Both cowbirds and finches are protected by the federal government. Without a permit, it is illegal to interfere with the eggs, nests or nestlings of either species. Thus your last suggestion Sue, about “letting nature take its course,” is your only legal, and probably best option. If you interfere with any bird’s nest, you are at risk of being investigated by the government’s Department of Nestland Security. And you don’t want to mess with those guys.