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What Carolina Wrens Like For a Nesting Box

Dear Bird Folks,

Is there a house for Carolina Wrens?

– Jay, Dennis, MA


It’s tricky, Jay,

Unlike House Wrens, Carolina Wrens typically don’t use traditional birdhouses. For some reason, those customary round entrance holes don’t appeal to them. But a few years ago, I found plans specifically for a Carolina Wren birdhouse. The box wasn’t anything special, except there was no round hole. The birds entered via a slot near the top, like books through a library drop box. For the sake of science (and sales), I decided to ask my birdhouse guy (yes, I have one of those) to build a few of them. Once completed, I put one of the boxes under an overhang above my backdoor (as wrens like to be hidden), and waited. I didn’t have to wait very long, because birds immediately began using it. Great, right? No, not great.

Unfortunately, instead of wrens, my test box attracted House Sparrows. Some people (Brits) might have been okay with this, but the invasive House Sparrows are a huge problem for many of our native birds. In order to keep the sparrows from completing their nest, I blocked the entrance slot with a balled-up clump of aluminum foil. (My wife just loved the way it looked…not.) The plan was to eventually remove the box, but if there is something I’m good at, it’s procrastinating. Two years later, the box is still in place. This spring, Casey told me that the sparrows were back. Grrr! It was time for the box to come down for real this time. But just as I was getting ready to climb the ladder, Casey told me to hold on. He cautioned me that the fast-flying brown birds might also be wrens. I put the ladder away.

Cape Cod has two species of “backyard” wrens. We have the House Wren, which is brown, and that’s all. The Carolina Wren has a brown back, a buffy belly and a significant white stripe above each eye. In addition, the male Carolina Wren has one of the biggest mouths in the animal kingdom. Weighing less than 3/4 of an ounce, he has the vocal impact of Bernie Sanders…with a megaphone. Each day, from sunup ‘til sundown, the male sat on my porch railing and yelled his signature song, nonstop. Even though I never saw him go into the box or even gather nesting material, his endless chatter convinced me that his mate was sitting on eggs. I spent a fair amount of time watching, but saw no activity. I even moved directly under the box and still saw nothing. I next tried to spook the bird by whistling, clamping my hands and yelling, “ding-dong!” as if I was selling Avon, but there were no signs of life in the box. I hated to be such a nosy landlord, but for the sake of my birdhouse study (and this column), I needed to know if the box was occupied. Finally, I took a long stick and tapped the side of the box. Bingo! A rather irate female wren flew out. I apologized to her and promised never to go near her nest again. Although, I don’t think the male believed me since he kept yelling, which he probably would have done anyhow.

I wasn’t done watching the wrens, however. On the contrary, I was more obsessed with them than ever. To lure them in, I put out a small tray of mealworms. (Most people use mealworms to feed bluebirds, but in my yard, bluebirds are only a myth.) The worms attracted lots of birds (catbirds, cardinals, chickadees), but no wrens (or bluebirds). Eventually though, the female found the worms, but instead of eating them, she flew away with a mouthful, indicating that she had hungry mouths to feed. Once again, Bingo!

More often than not, it was the female’s job to carry the worms to the chicks (the male was too busy yelling at everyone). Surprisingly, she didn’t fly directly to the nest. After snagging a worm, she would hop along our deck or climb all around our lawn furniture, like a nuthatch (a drunk nuthatch), before finally zipping off to the nest. Was this misdirection a ploy to keep her nest hidden from me? Maybe, but the misdirection wasn’t necessary. I kept my word and only watched the nest from across the yard. From this vantage point I could observe the birds without interfering with their normal behavior, and I saw some interesting stuff. For example, whenever a Blue Jay went near the nest, the wrens would scold it, nonstop. Surprisingly though, they showed virtually no interest in Gray Squirrels. Unlike the rest of the world, they were totally at peace with squirrels. But anytime a chipmunk showed its face, they would dive at it like fighter planes. It was pretty funny, but the poor, scared chippies didn’t find any humor in it.

For the next few weeks, I would put out mealworms and watch the wrens carry them off to the nest. Then one morning, the female grabbed a worm and made a beeline to the nearby thickets. It didn’t take a wizard to figure out that her babies were now able to fly on their own…at least as far as the thickets. For a few more hours the parents came and went for worms. Then they stopped. I could still hear the male doing his usual screaming, but slowly his voice became more distant. His kids were on the move, and while I was sad to see them go, I have to admit it was good to get a break from the old man’s intense yelling. (I heard enough of that when I was growing up.)

Would I recommend this odd wren box, Jay? Probably not. Wrens are interesting birds, but who knows if they were attracted to the box, or the location or the mealworms. But if you want to try one of these boxes, you should contact my wife. She has a balled-up clump of aluminum foil that she’d love to get rid of.