Bird Watcher's General Store

The Magic Song of the Wood Thrush
Is Being Lost Due to Declining Habitat
08/06/10


Dear Bird Folks,

When I was a kid I used to hear the beautiful song of the Wood Thrush in the woods near my house. Now I don’t hear it anymore. Has something happened to them or have my ears become so bad that I simply can’t hear bird songs anymore?

– Floyd, Greenfield, MA

Part of the problem could be your ears. As we get older, it becomes more difficult for some of us to hear higher frequencies, especially the frequencies found in many bird songs. I’m not saying you’re old, but your name suggests you probably aren’t a teenager. There are kids hanging out in my house everyday and I’ve never heard one of them tell me that Floyd is coming over to play video games. However, if I go to the post office early in the morning there’s always a pod of retired men yapping out front and at least half of them are Floyds. There are also a few Clydes, a couple of Harrys and one Buster. I try to avoid Buster.

If I could somehow play the song of the Wood Thrush, so everyone who is reading this column could hear it, I’d bet most people would stop and say, “Hey, I’ve heard that song before.” I’d also bet that just about everyone would have an image of where they first heard the song. Just as the smell of balsam reminds folks of Maine, Christmas or cheap air fresheners, the unforgettable song of the Wood Thrush brings back memories of walking in the woods on a summer’s evening. Wood Thrushes are chubby, medium-sized songbirds. They are closely related to the American Robin, and in poor light the two birds look rather similar. In good light it’s easy to see that robins have slate-black backs and their signature brick-red breasts, while Wood Thrushes have rusty-brown backs and spotted fronts, looking like a sloppy house painter. The Wood Thrush’s habitat of choice is not our front lawns but deep, dark woodlands, where they spend most of their day on the ground searching for food. The forests in which these birds breed are often so dense that they can’t be seen, even by each other. To compensate for this lack of visibility, the thrushes have developed a song that not only helps them attract a mate but is one of the most haunting sounds in the bird world.

When I say the Wood Thrush’s song is “haunting” I’m not exaggerating. Their echoing song seems to appear out of nowhere and magically drift through the forest like early morning fog. Researchers have long wondered how the birds are able to produce such complicated sounds. Like most birds, thrushes have a syrinx, or voice box, which contains two membranes that the birds vibrate when they want to sing. However, unlike most birds, the Wood Thrush is somehow able to separately control the vibration of each membrane, producing two distinct sounds at one time. The bird essentially sings a duet with itself, which explains its colloquial name, “The Sonny and Cher Thrush.” Actually, that’s a name I just made up, so you probably won’t find it in many bird books…yet.

Unfortunately, the population of this musical wonder has been declining over the past few decades. In some locations the number of breeding thrushes has dropped by nearly forty percent. As you may have guessed already habitat change is a big part of the problem. Wood Thrushes spend the colder months in Mexico and Central America, where clear cutting has negatively altered their wintering grounds. Thrushes typically return to the same forests each winter. If the forests have become, say, orange groves, it forces the birds to find a new place to live in the winter. Many of these displaced birds will spend the winter wandering the tropics and may eventually fall victim to predation and never fly north again.

The birds that do return to North America must now deal with changes we’ve made to their breeding grounds. Many of their secluded forests have become a patchwork of roads, homes and wood lots. Even though Wood Thrushes are fairly tolerant of humans, that tolerance comes with a price. The closer the birds nest to humans the more likely they will fall victim to other creatures that also tolerate humans. High on that list of predators are raccoons and house cats, but the number one troublemaker is the Brown-headed Cowbird. Cowbirds, of course, don’t eat thrushes, but they do lay their eggs in their nests. For whatever reason, the adult thrushes don’t notice that they have laid three beautiful blue eggs and one ugly brown one. The trusting adults hatch all the eggs, then feed and raise whatever comes out them, which is often to the detriment of the little thrushes.

Whether your ears are in good shape or not, Floyd, it is becoming more and more difficult to hear the duet-sounding song of the Wood Thrush. But don’t give up trying to hear them. Their amazing song is worth going out of your way to hear. In fact, the folks in the District of Columbia enjoy the Wood Thrush so much they have made it their official “state” bird. You gotta love that. The lawmakers in Washington have chosen to honor a bird that is able to talk out of both sides of its mouth at once. How perfect.




Artwork by Catherine Clark


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