How to Know the Birds: No. 8, Why Do Carolina Wrens Sound So Loud?

I had every intention of sleeping in. I’d flown in late the night before and had nothing planned for the morning.

The Carolina wren had other plans. At 5:39 local time (that’s 3:39 body time), the bird went off. Then a pause of 6–7 seconds, and again. It went on and on like this, the worst part being those pauses. I can sleep through the steady din of robins and house sparrows (they were out there too), but the wren was like a slow motion car alarm.

I wouldn’t be getting back to sleep. And I got to wondering: Why do Carolina wrens and other birds sound so loud when I’m Back East?

A Carolina wren brays outside the bedroom window of the house in which the author grew up. Why do wrens and other birds always sound so loud Back East? Audio by © Ted Floyd.

Years ago, I’d hit upon altitude and humidity as possible culprits. I’ve lived for many years in the Denver metro area, where the air is famously high and dry. That makes a huge difference in so diverse aspects of daily living—from hitting baseballs out of Coors Field to landing planes at DIA to cooking quinoa and brewing kombucha in our Boulder bungalows. Could it be the same with birdsong? After a fair bit of asking around, and even solving some physics equations, the best I can come up with is: It’s complicated.

The place where I was staying—the place with the Carolina wren—is fantastically complex from an acoustics standpoint. Homes and buildings, steep hillsides with tall trees dripping with overnight rain, basically all the infrastructure of a big city in the upper Ohio River valley. Yes, I was back in my hometown of Pittsburgh—for “spruce budworm warblers” and my mother’s 80th birthday party, not necessarily in that order. All those objects in the environment have significant effects on how humans and birds hear birdsong. Ornithologist Paul Handford, working in South America, has shown how whole populations of rufous-collared sparrows change their songs in response to ongoing habitat change: Subtract trees from the landscape (deforestation) or add them (recovery therefrom), and the sparrows change their songs.