Bird Songs

My eyes are still closed when I hear catbird filling our backyard with a rich, complicated jumble of his favorite songs, squeaks, and squeals. It is 4:15 a.m. and lying in bed listening to a seemingly endless variety of his cheerful sounds, I think there is no more glorious way to begin a day. Catbird’s songs exuberantly announce his gender and species, and his ownership of a particular piece of real estate. Earlier in the spring, he would have sung to attract a female, but we have seen two catbirds darting in and out of the thick shrubbery where they nest every year, so we think his mate has arrived and they are already nesting. His song this morning more likely is directed at any potential rival males, telling them to move along out of his territory.

Birds use a wide variety of sounds to communicate. Turkey vultures are mute, lacking a voice box. When they have something to say, they hiss. Many species have a simplified voice box that allows them to vocalize, but not sing. According to Paul R. Erlich, David S. Dobkin, and Darryl Wheye, authors of the classic Birder’s Handbook, A Field Guide to the Natural History of North American Birds, woodpeckers communicate by distinctive calls, and by drumming with their bills on various surfaces or hollow tree limbs to produce different sounds. Crows and ravens can call, but not sing, and they clack their bills to make sounds. A few species even make sounds with their tail or wing feathers. During courtship flights, the American woodcock and Wilson’s snipe spread out specialized feathers, causing the air rushing past them to make whistling sounds. The male ruffed grouse makes loud booming sounds by striking the air with cupped wings, which he flaps rapidly forward and upward.

In order to sing, birds need a complex vocal apparatus called a syrinx, which allows them to control the volume and pitch of sounds, and even to produce more than one sound at a time. Unlike the human voice box or larynx, which is located at the top of the windpipe, or trachea, the syrinx is a bony sac located at the bottom of the bird’s trachea. Often located deep within the breast of the bird, the syrinx is a resonating chamber controlled by specialized muscles, and surrounded by a resonating air sac. The muscles controlling the syrinx control the tension on highly elastic vibrating membranes that act like the skin of a drum. Each side can be controlled independently, allowing some birds to produce two simultaneous sounds. The birds we know as songbirds are divided into two groups, depending on where and how the syringeal muscles are attached. One arrangement allows certain species, including catbird, to sing complicated and elaborate songs. Another arrangement allows other species to produce flutelike or whistling types of songs. According to Donald Kroodsma, author of The Singing Life of Birds: The Art and Science of Listening to Birdsong, songbirds, with highly complex voice boxes, and highly developed brains, are the master singers, capable of learning songs.

Other birds, approximately 1,100 species, also sing, but have less complex vocal mechanisms, and sing less complicated songs. According to Kroodsma, these birds are incapable of learning songs. The songs they sing are inherited, passed down from one generation to another in their genetic material, and these songs do not change. The eastern phoebe, that nests in our yard, belongs to this group. His songs are hard-wired in his genes, and they are the songs he will always sing, with no variations.

A catbird, that is capable of learning and inventing new songs, occasionally adds to his repertoire. Two crows caw loudly from somewhere high in the white pine tree, clacking their bills rapidly as if they were castanets, and by the time phoebe starts belting out the same few familiar phrases of his ancestral song, we are all fully awake, and ready to begin a new day.

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