The Mystery Of Roosting Wrens

Story and illustration by Doug Pifer

Just before I let the dogs out, I turned the porch light on and saw something that looked a lot like a pinecone resting on top of the corner post next to the porch ceiling. I recognized it because I’d seen the same thing there several years ago—a roosting Carolina wren.

Carolina wrens are abundant year round in the Shenandoah Valley. They’re familiar to rural folks for a tendency to build their mossy nests in unlikely nooks and crannies. At our place wrens have built nests and raised their young in a pocket of a barn jacket hung in a shed, under a plant in a hanging basket, and under the protective cover of a propane fuel tank. Unlike the migratory little house wren, a Carolina spends the winter here, often in the same territory it nests in.

How such small birds as wrens survive cold winter nights is miraculous. Even the hardiest of them must find a warm dry place to roost in the worst weather. Wrens and other cavity nesting birds often roost in their former nests or those of other birds. But sometimes they sleep out in plain view, like this one.

The first time I saw one roosting on top of the porch post, I had no idea what it was. It certainly didn’t look like a bird. Almost the size of my balled up fist, the object was round, dark, and covered with white specks like a ball of black string with tiny bits of white cotton scattered through it. Only when I walked up to investigate did it shrink down into a bird. I recognized the white eyebrow and rufous back of a Carolina wren in that instant before it flew off into the autumn night.

Many small birds fluff the feathers on their lower backs to cover their wings and bodies on cold winter nights. Presumably this helps them conserve energy and keeps their tiny bodies from losing vital heat, like sleeping under a down comforter. Chickadees, juncos, and other small species roost this way in trees among dead leaves or thick branches. A bird fluffed up to this extent, with its wings and its head completely hidden within the feathers, looks several times bigger than its natural size.

But unlike these other birds, a fluffed up Carolina wren shows luminous-looking white spots that are invisible when its feathers are in their natural daytime position. These spots make the roosting bird resemble a pinecone or some furry, spotted mammal.

Researching this subject, I came upon many photos and several blogs from other naturalists describing the mystery of the white spots on roosting Carolina wrens. A couple of them proposed theories as to why these wrens might behave and look this way, either for warmth or for camouflage. None had been able to reach a scientific conclusion.

For me, the thrilling thing about nature is just being able to see a plant or an animal being itself or doing something amazing. Knowing exactly why isn’t so important.