Be mite particular in cleaning nests

House wrens and spiders have a working relationship.

The wrens employ baby spiders as pest-control crews. The spiders eat mites, which is a good thing, because as many as 50,000 mites can be found in a single wren nest. Remember that number.

This unusual relationship came to mind recently when I was cleaning the wren nest boxes in our yard, after the breeding season was over.

We place one artificial cavity in each corner of our yard. Male wrens tend to choose a territory that offers multiple nesting cavities, natural or store-bought. They build partial nests in at least two of the cavities, usually more. Our male built in all four of our boxes.

A female wren is attracted to an area by a male's singing. But the female apparently pays more attention to the nests than to the male. She wants at least two nesting cavities from which to choose.

If she is happy with the real estate, she stays. And he, apparently, accepts any female who likes his taste in dwellings. If it's good enough for her, she's good enough for him.

"Apparently" is a good word to use when discussing the biology of many bird species. House wrens are among the most thoroughly studied of North American birds, in part because nest boxes make them readily available for research. Yet so much about them is unknown or uncertain.

Wren house hunting

Though the spiders do an admirable job on the mites, the nest boxes still need to be emptied in the fall. I went out to clean them.

In the first box, I found half a dozen twigs, two spider egg sacs and four small pieces of Styrofoam. Box No. 2 had more twigs. Box No. 3 had a partially constructed nest. Box No. 4 is where the male and his partner took out a mortgage. They chose one of my PVC boxes, 4 inches in diameter, 6 inches from the base to the entry hole.

The box was filled with twigs above that entry. Peeking in, it looked like a jumble.

But when I removed the nest, I thought it looked like an anklet made of twigs -- several hundred twigs. There was the opening at the top where the foot (or the bird) would enter, then an unobstructed tunnel to the toe. At the bottom the female had used grass, bark, hair and feathers to soften her nest.

Use caution when cleaning

I don't like mites, lice, chiggers or other crawly vermin, so I'm careful when I clean nest boxes in the fall. I use a narrow, long-handled mason's trowel to remove old nests. And I often wet the box contents first to discourage foul fowl dust.

Of course, I learned to be so cautious the hard way.

Many years ago, some barn swallows nested on top of a porch light above my back door. When the young birds had fledged, I decided to get rid of the nest. I stood underneath it and casually gave it a whack to knock it down.

A mist of live mites descended on me, dropping into my hair, my ears, down my shirt, in my shoes. Fifty-thousand is a conservative estimate.