Excerpt

The Genius of Birds

Jennifer Ackerman

April 25, 2016 
The following is from Jennifer Ackerman’s book, Genius of Birds. Jennifer Ackerman has been writing about science, nature, and human biology for almost three decades. Her most recent books include Sex Sleep Eat Drink Dream: A Day in the Life of Your Body; Ah-Choo: The Uncommon Life of Your Common Cold; Chance in the House of Fate: A Natural History of Heredity; and Notes from the Shore.

All birds vocalize. They hoot, yodel, caw, wail, rattle, chit, seet, and sing like angels. They call to warn of predators and to identify family, friends, and foes. They sing to defend their territory—to stake it out or fence it in—and to woo a mate.

Calls are typically short, simple, succinct, and innate (like a human scream or laughter), uttered by both sexes to make their point. Songs are generally longer, more complex, and learned, sung normally in tropical regions by both males and females, and in temperate climates more commonly by males only during the breeding season. But there is no neat division between call and song, and there are plenty of exceptions. The calls of crows fall into a dozen different categories—rallying, scolding, assembling, begging, announcing, dueting, among others—and some are learned. For sheer complexity, the calls of the black-capped chickadee far and away beat out a great tit’s two-tone song.

But singing is something special. “Nearly all animals that communicate vocally do it by instinct,” says Jarvis, who studies vocal learning at Duke University. “They are born knowing how to scream or cry or hoot.” These utterances are innate or imprinted, like a sheep’s baa. “Vocal learning, on the other hand, involves the ability to hear a sound and then, by using muscles of your larynx or syrinx, to actually repeat that sound yourself,” explains Jarvis, “whether it be a sound learned in speech or the note of a birdsong.”

Close to half the birds on the planet are songbirds, some four thousand species, with songs ranging from the mumbled melancholy chortle of the bluebird to the forty-note aria of the cowbird, the long, byzantine song of the sedge warbler, the flutelike tune of the hermit thrush, and the amazing seamless duets of male and female plain-tailed wren.

Birds know where to sing and when. In the open, sound travels best a few feet or so above the vegetation, so birds sing from perches to reduce interference. Those singing on the forest floor use tonal sounds and lower frequencies than those singing in the canopy. Some use frequencies that avoid the noise from insects and traffic. Birds living near airports sing their dawn chorus earlier than normal to reduce overlap with the roar of airplanes.

* * * *

In his poem “Ode to Bird Watching,” Pablo Neruda asks, “How / out of its throat / smaller than a finger / can there fall the waters / of its song?”

Because of a single invention.

It’s a unique instrument called a syrinx, after the nymph transformed into a reed by Pan, god of fields, flocks, and fertility. Scientists took a long time figuring out its details because the syrinx is buried deep in a bird’s chest, where the trachea splits in two to send air to the bronchi. Only in the past few years did researchers finally produce a stunning high-resolution three-dimensional image of the organ in action, using magnetic resonance imaging and microcomputed tomography.

The high-tech image revealed a remarkable structure. It’s made of delicate cartilage and two membranes that vibrate with airflow at super-fast speeds—one on each side of the syrinx—to create two independent sources of sound. Gifted songbirds such as the mockingbird and canary can vibrate each of their two membranes independently, producing two different, harmonically unrelated notes at the same time—a low-frequency sound on the left, a high-frequency sound on the right—and shifting the volume and frequency of each with such breathtaking speed as to produce some of the most acoustically complex and varied vocal sounds in nature. (This is quite extraordinary. When we talk, all of our pitch, all the harmonics of our vocalizations, move in the same direction.)

All of this is managed by minute but powerful muscles. Certain songbirds, such as European starlings and zebra finches, can contract and relax these tiny vocal muscles with submillisecond precision—more than a hundred times faster than the blink of a human eye. This feat of fast-muscle contraction has shown up in only a handful of animals, including the sound-producing organ of rattlesnakes. The winter wren, a little brown bloom of a bird known for its swift song delivery, sings as many as thirty-six notes per second—far too quick for our ears or brain to perceive or absorb. Some birds can even manipulate the syrinx to mimic human speech.

Birds with a more elaborate set of syringeal muscles tend to produce more elaborate songs. The mockingbird in that cedar tree has seven pairs that allow him to perform his vocal gymnastics over and over with seemingly little effort—seventeen, eighteen, nineteen songs per minute when he really gets going. Between the notes, he takes tiny breaths to replenish his air supply.

His phantasmagorical song may be executed by his syrinx, but it’s initiated and coordinated by his brain. Nerve signals from an elaborate network of brain areas control each of the muscles, coordinating nerve impulses from his left and right brain hemispheres to the muscles in the two halves of his syrinx, creating just the right airflow in each necessary to produce the hundreds of different imitated phrases he sings.

He makes it all look so easy.

But think about it. To imitate a phrase, say, in German or Portuguese, you have to listen carefully to the person uttering it. You have to hear it accurately. Not such an easy task, Tim Gentner tells the roosting bird specialists at Georgetown, especially if you’re at a cocktail party or on a noisy street, where you have to pick it out from a cacophony of sound, a phenomenon called “stream segregation.” Birds put up with a lot of this partylike pandemonium, especially at peak times of song, like the dawn chorus. “Many birds are social creatures; they’re communicating with one another in relatively large groups,” says Gentner, a psychologist at the University of California, San Diego. “There’s a lot of signal, and not all of it is useful to every individual at every point in time, so one important task is to figure out which acoustic streams are carrying information.”

Once you’ve segregated a target phrase from all that din, you have to hold it in your mind while your brain translates the sound into a set of motor commands. It sends these to your larynx in the hopes that it will produce a similar sound. Rarely do you get the phrase right the first time. It takes practice, trial and error, hearing your own mistakes and correcting them. If you want to retain the phrase, it means repeating it often enough to reinforce the brain pathways that created the memory in the first place. And if you want to remember it for life, you must file it away in a safe long-term-storage place.

Mockingbirds are really, really good at all this. The proof is in the sonograms or spectrograms. These are visual printouts of sound (with frequency or pitch on the vertical axis and time on the horizontal axis) that scientists use to detect subtle differences in birdsong. Sonograms comparing a prototype song and the mockingbird’s copy show that the imitator sings nuthatch and thrush and whip-poor-will with almost perfect fidelity to the original script. Scientists found that when a mockingbird sings a cardinal’s song, it actually mimics the muscular patterns of the cardinal. If the notes of his model fall outside his normal frequency range, he substitutes a note or omits it, lengthening other notes to match the song in duration. And if he’s facing a too-rapid-fire delivery of notes such as a canary’s, he clusters the notes and pauses to breathe while still maintaining identical song length. That may not fool the whip-poor-will or thrush, but it fools me.

Of course, the mockingbird is not the only mimic in birddom. A cousin Mimidae, the brown thrasher, by some accounts can mimic ten times the number of songs a mockingbird sings, though not with such accuracy. Common European starlings are also accomplished mimics, as are nightingales, which can imitate some sixty different songs after hearing each only a few times. Marsh warblers are known to sing a wild, urgent, international pastiche of a song peppered with the tunes of more than one hundred other species. Some of the songs are European, picked up at its nesting grounds, but most are African, plucked from the neighborhoods of Uganda, where it spends its winters. Its imitated songs of the Boran cisticola, vinaceous dove, and brubru shrike create a kind of acoustic map of its African travels.

The lyrebird is renowned as a champion sound thief. As one naturalist noted, it’s a startling experience to be walking in the Australian forest when suddenly you’re confronted “by a fowl-like, brown bird which may bark at you like a dog.” The fork-tailed drongo, that brainy African bird that dupes the pied babbler, mimics the alarm calls of not just the babblers but a startling number of other species in a similar ploy—to scare honest birds or mammals off their hard-won morsels, which the drongo then steals.

There are reports of a bullfinch trained to sing “God Save the King,” a gray catbird sounding taps (which it may have picked up from burial services at a nearby cemetery), and a crested lark in southern Germany who learned to imitate the four whistling notes a shepherd used to work his herding dogs. So faithful were the imitations that the dogs instantly obeyed the bird’s whistled commands, which included “Run ahead!” “Fast!” “Halt!” and “Come here!” These whistled calls subsequently spread to other larks, creating a little pocket of local “catchphrases” (and, quite possibly, some very winded sheepdogs).

Some birds have an exceptional gift for imitating human speech. The African grey parrot is one such species. The mynah certainly qualifies, as does the cockatoo. These few are generally considered the Ciceros and Churchills of birds. Arguably, there are a few others in the corvid and the parrot families: parakeets, for instance. The New Yorker once reported that “after weeks of silence, the first words uttered by a Westchester parakeet were, ‘Talk, damn you, talk!’”

Imitating human sounds is a lot to ask of a bird. We form vowels and consonants with our lips and our tongue, among the strongest muscles per inch in the human body. For birds, with no lips and with tongues that generally aren’t used for making sounds, it’s a tall order to take on the nuances of human speech. This may explain why only a handful of species have accomplished the skill. Parrots are unusual in that they use their tongues while calling and can manipulate them to articulate vowel sounds, talents that probably underlie their ability to mimic speech.

The African grey parrot is the parliamentarian of the bird world. Irene Pepperberg made African greys and their speech abilities famous through her work with Alex, perhaps the world’s most renowned talking bird. Pepperberg would intermingle different sorts of questions about objects and Alex could answer with near perfect specificity. For example, if she showed him a green wooden square, he could say what color it was, what shape, and, after touching it, what it was made of. He also cottoned to phrases he heard around the lab, like “Pay attention”; “Calm down”; and “’Bye, I’m gonna go eat dinner, I’ll see you tomorrow.”

Alex was not alone in his badinage. One African grey I know, Throckmorton, pronounces his name with Shakespearean precision. Named for the man who served as an intermediary for Mary, Queen of Scots (and was hanged in 1584 for conspiring against Queen Elizabeth I), Throckmorton has a wide repertoire of household sounds, including the voices of his family members, Karin and Bob, which he uses to his advantage. He calls out Karin’s name in a “Bob voice” that Karin describes as spot-on; she can’t tell the difference. He also mimics the different rings of Karin’s and Bob’s cell phones. One of his favorite ploys is to summon Bob from the garage by imitating his cell phone ring. When Bob comes running, Throckmorton “answers” the call in Bob’s voice:

“Hello! Uh-huh, uh-huh, uh-huh.”

Then he finishes with the flat ring tone of hanging up. Throckmorton imitates the glug, glug sound of Karin drinking water and the slurping sound of Bob trying to cool his hot coffee while he sips it, as well as the bark of the family’s former dog, a Jack Russell terrier dead nine years. He has also nailed the bark of the current family pet, a miniature schnauzer, and will join him in a chorus of barking, “making my house sound like a kennel,” says Karin. “Again, he’s pitch perfect; no one can tell it’s a parrot barking and not a dog.” Once, when Bob had a cold, Throckmorton added to his corpus the sounds of nose blowing, coughing, and sneezing. And another time, when Bob came home from a business trip with a terrible stomach bug, Throckmorton made sick-to-my-stomach sounds for the next six months.

For one long stretch, his preferred “Bob” word was “Shhhhhhhhiiiit.”

Parrots have been known to teach other parrots to talk smack. Not long ago, a naturalist working at the Australian Museum’s Search and Discover desk reportedly took a number of calls from people who had heard wild cockatoos swearing in the outback. The ornithologist at the museum speculated that the wild birds had learned from once-domesticated cockatoos and other parrots that had escaped and survived long enough to join a flock and share words they had picked up in captivity—if true, a fine example of cultural transmission.

 

From GENIUS OF BIRDS. Used with permission of Penguin Press. Copyright © 2016 by Jennifer Ackerman.


More Story
Shakespeare is Dead: Six Hot Takes It's hard to believe it's been 400 years since Shakespeare died. It feels like only yesterday Polonius saw us off to college,...