Birdsong

Book by Stap Don

Chapter One

Several years ago on a Sunday afternoon I wandered through the one-story cinder-block building at one of the most famous addresses in bird studies -- 159 Sapsucker Woods Road: Cornell University's Laboratory of Ornithology. I had been let in, the door locked behind me, and I had the place to myself. To research an article I was writing on birdsong, I planned to review some of the literature in the lab's private library, including materials that were available nowhere else, but within minutes I found myself drawn to another kind of archive. Passing through an unlit hallway hung with the paintings of Louis Agassiz Fuertes, the greatest of bird artists, and an early associate of the lab, I made my way to the southeast wing of the building and opened the gray metal door to Room 125. Stepping inside, I felt a rush of cool, dry air. The windowless room, tightly packed with rows of metal shelves, was austere: white walls, a cement floor, exposed ductwork and girders, and bare lightbulbs hanging from the ceiling. It had the sterile functionality of a hospital room, and it appeared, if anything, cleaner and more orderly. The only sound was air moving through the vents. It would have been difficult to imagine a more lifeless space, yet all around me, stored on wall-to-wall shelves, was the aural life of the planet. This was the archive of the Macaulay Library of Natural Sounds, the largest collection of its kind in the world. The shelves, which rose above my head, contained more than 130,000 individual recordings, some in neatly labeled boxes containing seven-inch reels of tape, others on standard cassettes in makeshift containers with hand-scribbled labels.

Walking down the narrow aisles, I found boxes that held the sounds of crickets chirping, mountain gorillas thumping their chests, triggerfish squirting water, and prairie dogs barking. It was birdsong, though, that had drawn me there, and birdsong that dominated the Library of Natural Sounds. There, arranged taxonomically from ostrich to raven, were the songs of nearly six thousand of the world's nine thousand or so species of birds. On one shelf were the babbling-brook arias of mockingbirds, on another the flutelike ee-oo-lays of wood thrushes, and on others the wistful melodies of white-throated sparrows, the caroling of robins, and the songs of birds I had never seen nor heard: the superb lyrebird, laughing kookaburra, black-and-gold cotinga, snowy-headed robin chat, and more. If I looked, I could find the sounds of my childhood, the ok-ka-leee of a red-winged blackbird and the squeaky-gate call of a blue jay. And somewhere, surely, was Keats's nightingale and Shelley's skylark. The room was brimming with sound. But of course I heard nothing. The silence was profound.

This archive of sounds is invaluable. A second set of recordings made from these originals is kept in a vault in a limestone cave for safekeeping. Several recordings hold the voices of birds now extinct. Many are the only known aural records of rare and elusive species. Recordings like these are critical in one of the newest fields in zoology: bioacoustics, the study of how animals use sound to communicate. In recent years, scientists have discovered that elephants use infrasonic sounds to send messages across great distances; that hippos are able to communicate simultaneously in water and air; that small insects known as treehoppers send vibrations through the stems of plants to communicate with other treehoppers; that vervet monkeys use one kind of alarm call to signal that a leopard is nearby and a different one to signal the presence of a snake. But it is birds that have attracted the most attention. It has always been birdsong that has most enthralled and mystified us. Frogs croak, crickets chirp, wolves howl, and lions roar, but birds sing.

Today, many ornithologists are listening to bird vocalizations and studying their intricacies in ways that were beyond the grasp of their predecessors only a generation ago. Avian bioacoustics has flourished in just the last few decades, a result of two inventions from the mid-twentieth century: the tape recorder and the audiospectrograph, or sonograph. The latter, which produces a visual representation of sound, allows ornithologists to measure the details of a bird's song as concretely as Darwin measured the beak of a finch. These tools make it possible to look for answers to some ancient questions: Why do birds sing? What do their songs mean?

Bird "songs" -- typically an elaborate series of notes, often musical to our ear -- are delivered almost exclusively by the male of the species in the breeding season and sung repeatedly for prolonged periods; in contrast, bird "calls" -- relatively simple, brief vocalizations -- are made by both males and females to influence behavior in particular contexts (nestlings begging for food or geese honking in flight to coordinate the movement of the flock). Naturalists have long recognized that birds in temperate zones begin singing each spring when they are forming pairs, mating, and rearing young, so the common thinking was that the function of a bird's song was to romance a mate. In the 1930s a series of studies by a British naturalist, H. Eliot Howard, confirmed that birds are territorial. It's now known that a release of hormones, triggered by the lengthening of days during spring, spurs male birds to begin singing to announce their presence to other males. The dueling arias, sometimes punctuated with physical skirmishes, establish territorial boundaries. To females in the vicinity, the same songs (in most cases) brim with that most essential lust: the desire to reproduce oneself. Thus, male birds sing both to claim territory and attract a mate.

But the question is larger than this. Why do birds sing? Why have they come to rely on this particular means of communication? One line of thinking connects song with flight. Flying takes a great deal of energy. Song is an energy-efficient way to advertise and defend a territory. A bird need not fly from boundary to boundary to ward off interlopers. It can sit in one spot and sing. There are other ways to ask the question. Why do some birds sing, and others not? Why don't eagles sing like robins? Why does the chestnut-sided warbler sing one song before dawn and switch to another at sunrise? Furthermore, if the functions of birdsong are only to claim a territory and attract a mate, why do chipping sparrows sing one song but marsh wrens sing fifty or more? If both species are equally successful in defending territories and reproducing, what good are those extra forty-nine songs for the marsh wren? Why do mockingbirds continue learning new songs throughout their lives and imitate the songs of other birds? Why in some species -- cardinals, Baltimore orioles, rose-breasted grosbeaks, among others -- do females sing as well as males?

I left the Lab of Ornithology that Sunday afternoon with more questions than I'd arrived with. A few weeks later, I flew to Cape Cod, boarded the 6:15 ferry to Martha's Vineyard, and followed the winding, hilly roads to Gay Head, on the west edge of the island. I arrived shortly before dusk at a summerhouse overlooking an inlet. University of Massachusetts professor of biology Don Kroodsma had rented it for the weekend and invited me to join him and several biologist friends for what he called, more seriously than not, a party. With Kroodsma that evening were Jan Ortiz, a naturalist from Amherst; Linda Macaulay, an experienced natural sound recordist; Sylvia Halkin, a professor of biology from Central Connecticut State University; Curtis Marantz, one of Kroodsma's graduate students; and Bruce Byers, who had recently completed a Ph.D. at the University of Massachusetts. Still more of Kroodsma's friends were to arrive the next day.

The "party" began about the time others might be ending -- 3:30 A.M. I rose, startled by the alarm clock, and turned on the bedside lamp. The house was silent except for a rustling in the kitchen where I found Kroodsma. There was no time for breakfast. Kroodsma was already headed for the front door carrying a backpack over his shoulder. With an efficiency that suggested he was accustomed to getting up at this hour, he quickly loaded up his car with a tape recorder, a parabolic microphone, and a bag filled with cable connectors, batteries, and other electronic gear. We drove off, Kroodsma intent on his mission: to explore the mystery of the song of the black-capped chickadee.

The chickadee is one of the best known and most common birds in North America, a tiny puff of white and gray with a black cap and chin. Its range encompasses the northern half of North America from Nova Scotia to British Columbia, and it is a frequent visitor to bird feeders. Consequently, its song and most common call -- a whistled fee-bee-ee and a buzzy chick-a-dee-dee-dee respectively -- are known by even the most casual observers of birds. Yet, many experienced bird-watchers and more than a few ornithologists would have been surprised to know there was any mystery regarding the chickadee's song. Clearly, they hadn't listened to it as closely as Kroodsma had.

Kroodsma, a tall, fit man in his fifties, has been eavesdropping on birds all of his adult life. He is widely regarded as one of the world's experts on birdsong. When I first called him to introduce myself and ask about his work, he quickly invited me to join him on Martha's Vineyard. The mystery of the chickadee's song, he said, was irresistible. I knew the song well, or thought I did, having grown up with it in the Midwest. Of the two whistled notes (fee followed by bee-ee), the first is delivered at a higher pitch than the second, and the second note is interrupted with a slight hesitation. The tone of the whistled notes and the descending pitch give it a wistful quality. Kroodsma, as hard-nosed as they come when he's thinking as a scientist, becomes wistful himself when he talks of the beauty of a bird's song. Under the spell of the chickadee's modest melody, and mindful that one func...