Little Brown Jobs

House Wren_ManitouLake-CO_LAH_4169Would you like your bedroom to be infested with spiders? I can’t count the nights I’ve spent wide awake in bed. staring at a suspicious black blob on the ceiling (I’m rather nearsighted without my glasses). Was it a spider? Should I turn on the light? It might move if I take my eyes off it to find my glasses. What if it is a spider? Is it going to fall on me in the middle of the night?

You can tell I don’t appreciate spiders in my bedroom. It’s a good thing, then, that I’m not a House Wren.

House Wren_GardenCity-KS_LAH_5334House Wrens are small, nondescript brown songbirds. They eat insects and spiders. Following the bugs, their population expands northward in summer, when they can be found in most of the U.S. and parts of Canada. Then, as the seasons turn, these northern birds head south, wintering in the southern states and central Mexico.  However, House Wrens can also be found all the way to the southern tip of South America! That makes them the most widely distributed bird in the Western Hemisphere.

With a bird that far-ranging, it’s no surprise that there are several distinct subspecies. Here in the U.S. we have the Northern House Wren, Troglodytes aedon aedon. There’s also the Brown-throated wren, T. aedon brunneicollis, found from Texas south throughout Mexico, the Cozumel Wren, T. aedon beani, endemic to the island of Cozumel, and the Southern House Wren, T. aedon musculus, which includes wrens from southern Mexico to Patagonia. And just to further complicate matters, some ornithologists (a minority at this time) consider these all separate species.

South American birds look pretty much like those summering in Canada, although those on the various Caribbean islands can appear quite dissimilar. But if the House Wrens are ever broken into differing species, it will be because of their songs. It’s unlikely that a bird from the northern end of their range would understand a bird from the southern end—the songs are that different.

House Wren_ManitouLake-CO_LAH_4230rHouse Wrens make up for their small size with a big voice. I’m always amazed that so much volume can emanate from such a tiny throat! I most often see these wrens hopping among the lower branches of a large bush or small tree, where they hide among the twigs. It’s difficult to spot a quiet brown bird sitting in a brown shrub. Once it opens its mouth, however, there’s no mistaking that there’s a House Wren nearby. For the most part, they only sing during the breeding season, which is now. And it’s not just the males making the racket—the females also sing.

I just learned that the western Great Plains is House Wren central—with the highest density in North America. I believe it! Lately I’ve seen plenty of House Wrens, and they’ve all been quite busy building nests.

Our local wrens typically nest in abandoned woodpecker holes, although they’ll also move into nest boxes, tin cans, under eaves, or any place else affording shelter and protection from predators.  If nothing satisfactory can be found, these belligerent birds will choose an already-claimed spot and simply evict the current tenants. Not nice!

The nests are cup-shaped, and constructed of fairly substantial twigs. The male does the building, but his mate expresses her opinion of his construction by tossing out any twigs that don’t strike her fancy. Then she’ll line the nest with softer materials such as moss, hair, or even trash.

They don’t like competition. Once they’re settled in their cavity, they’ll fill up adjoining cavities with more twigs, barricading the hole to any potential neighbors. In addition, they’ll peck holes in the eggs of any intruders.

Once the babies arrive, hairless and helpless, it takes both parents to keep them fed.  It takes several weeks for the young to fledge, and the nest accumulates parasites—blood-sucking mites and insects that can harm, or even kill, the nestlings. This is where those spiders come in.

The adult wrens will carry spider cocoons into the nest cavity. The spiders eventually hatch. Being voracious predators, the spiders eat the parasites, and everyone lives happily ever after. Until the wrens eat the spiders.

The answer the last week’s quiz is Yellow-headed Blackbird.

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