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Taking note | Bird song and animal calls prove to be more than just sounds of music

Pam Dixon

2-Aug-2000 Wednesday

Since ancient times, humans have looked to animals as a source of inspiration, especially for music. In ancient Greece, Homerian singers named all manner of birds in their epic songs, including hawks, which they believed were the “messengers of Apollo.”

The fascination with birds continued, but the inspiration became more direct. Music containing actual bird song fragments and themes has permeated Western music since the 16th century, if not before.

Mozart had an avian muse, his famed starling. The story goes that Mozart purchased a starling, and then purportedly worked its songs and trills into later compositions. According to legend, the starling was able to sing the finale of the G Major Concerto, though the story has never been proved.

There is no doubt that animals, particularly birds, have influenced human music. But are musical-sounding animals such as song birds actually making music or are humans the only music makers on the planet? Scientists have delved deeply into this question.

“I think it’s fulfilling a romantic intent when someone reduces animals to our level. What they do with sounds has very much to do with their own business and sound structure,” says Thomas Eisner, director of the Cornell Institute for Research in Chemical Ecology. “I’m for really sticking to the fact that animals are inclined to be different than us, and that they are more interesting and enticing by virtue of their music. What a bird like a magpie learns is a function of what it hears at certain times. But because animals make musical sounds doesn’t make them composers or performers; it doesn’t even make them music critics.”

The scientific evidence falls firmly in Eisner’s corner. Study after study links the sounds that animals make to distinct behaviors and communications. And that’s where things begin to get interesting. When you drop the notion of animals as musicians and begin to look at their sounds as unique forms of language, a new world opens up.

Sex and violence

Bird song, because it has been studied extensively across species, has yielded many of its secrets to scientists. “Bird song is about sex and violence,” says Ron Weisman, professor of psychology and biology at Queen’s University, Canada. “It may sound nice to us, but it’s all about attracting mates and repelling territorial invaders.”

Scientists have learned that male birds are the singers, and they require a tutor at a young age in order to learn their species’ distinct battery of songs. Genetic testing has furthered songbird research, revealing precisely which male singers attract the most females. But some mysteries remain.

“We have not been terribly successful in explaining the differences between species,” says Michael Beecher, a professor of psychology and zoology at the University of Washington. “A (common) sparrow learns nine different songs, a white crown sparrow learns one song; marsh wrens have hundreds of songs, and then there are the birds who can mimic all sorts of songs.”

Beecher’s research has focused on how song sparrows use a shared selection of songs to communicate with neighboring birds. One of his recent discoveries is that birds tend to learn the songs that the birds near them are learning. The birds also use specific types of songs, shared or not, to communicate detailed territorial and mating information. “A given bird may share songs of types A, B and C with one neighbor, and he might share C, D, and E with another neighbor. This is what they seem to do. The birds speak different songs to different neighbors.”

It’s a song language that reveals much about the way birds perceive and use sound. An important aspect of bird song is the frequencies that are in it, says Eugene Morton, a researcher at the National Zoo and the Smithsonian Institute.

He has found that birds can hear things much more quickly than humans can, and birds are able to focus much more precisely on the frequency of each sound. “Some frequencies travel through the environment better than others, depending on habitat,” he says.

Birds that live in open, brushy country, for instance, use timing types of sounds such as trills and buzzes. Those sounds, while not nearly as musical to the human ear, allow those birds to prevail against the negative effects of their habitat.

“The most beautiful singers don’t occupy open habitats,” Morton maintains. “Musical birds are in the forest, where there isn’t the heating effect of the sun to deal with. Those birds can use the long whistles and frequencies in the midrange that are pleasing to human ears.”

Frequency is so important to birds, in fact, that scientists can identify species of birds in a region simply by the frequencies of their calls. “Songbirds hear relative pitch about as well as we do. But their ability to hear absolute pitch and detect a particular frequency is flat-out better than ours,” says Morton.

By “perfect pitch,” Morton is referring to an ability that is statistically very rare among humans. Most humans can hear relative pitch, that is, how far apart two notes are from each other. But very few humans have the ability to identify perfect pitch, or the frequency of a note, even though humans have the biological equipment to do so.

Musicians who have perfect pitch can, for example, hear a note played and can identify the name of the note unerringly.

Diana Deutsch, professor of psychology at UCSD, is one of the few scientists who have studied perfect pitch in humans. “I’m hypothesizing that we are all born with the ability to use perfect pitch, but we only develop it if we are driven to use it,” she says. “People who speak tone languages, for example, are far more likely to develop perfect pitch because they are using pitch to communicate.”

Tone languages are those like Vietnamese that rely on specific tones or frequencies for meaning of words. The same word spoken at a different pitch can have a completely different meaning, thus the need for perfect or near-perfect pitch. Deutsch recently discovered that fully one-third of native Vietnamese speakers have perfect pitch, which is an astonishingly high amount compared with nontone language speakers.

“I think the relationships between speech and music are much more profound than people realize,” says Deutsch, who notes that for musicians to have perfect pitch, they must have been exposed to music and note names very early in life. And to have perfect linguistic pitch, a person needs to have learned a tone-based language from birth or very near to birth.

Like most birds, humans need to learn musical information early in life for it to stick.

Long-distance calling

Whale song research is finally beginning to catch up to the bird research, thanks to advances in underwater recording technology. So far, little is known about whales’ use of perfect pitch to communicate. Researchers have discovered, however, that like birds, whales process sound faster than humans, and the connection between songs and behavior coincides eerily with that of birds.

Male humpback whales sing 10- to 15-minute-long, highly complex songs during breeding season, which lasts about a third of the year. Humpbacks learn their highly melodic songs within their unique social groups or pods, and they have a mysterious way of transforming and sharing songs among each other that is not completely understood.

“Whales’ song is a reproductive display by the males,” says Peter Tyack, senior researcher at the Woods Hole Oceanographic Institution in Massachusetts. “Each population of humpback whales has a distinct song that gradually evolves over time.”

Tyack, who has tracked humpback whales in the wild for two decades, says the whales’ songs change so distinctly over the course of one breeding season that he can tell the approximate date of the tape he’s listening to.

Thanks to their super-low frequency vocalizations, whales have amazing long-distance sound capacities. “We can hear humpback songs for at least 5 to 10 kilometers (3 to 6 miles), larger species even further. Finback and blue whales, which don’t congregate — they disperse in tropical oceans — make a loud, low-frequency song you can hear hundreds miles away.”

As in birds, the distinction between species that congregate and those that don’t appears to make a significant difference in how the animals’ vocalizations evolve. The songs that humans find most attractive tend to be those that are made for shorter-range communications.

Katy Payne, a bioacoustic researcher at Cornell, has found a great deal of similarity between elephants and the blue and finback whales. She notes that both whales and elephants make very low-pitched, powerful calls that travel long distances, up to several miles in the air for elephants, maybe more through the ground.

Payne discovered that elephants use ultra-low frequencies to sing songs that are inaudible to the human ear. Female elephants sing low-frequency songs of up to 45 minutes while in heat, attracting males from surrounding regions. The trumpeting sounds that elephants make are quite separate from the more mysterious low-frequency vocalizations, which range from about 5 herz to just above 14 herz .

King communicator

Among the keenest musical communicators in the animal kingdom are dolphins. While much remains to be learned, a study done by the Dolphin Institute found that dolphins can recognize similar tones spanning more than two octaves.

“Other than humans, no other animal species has been shown to recognize melodic sequences or sounds across octaves,” says Adam Pack, a dolphin researcher and the Dolphin Institute’s assistant director.

“Songbirds can recognize the same type of melodic sequence within the same octave. But if you change octaves, songbirds treat it as a new problem and they have to learn it again,” Pack says. “Dolphins spontaneously recognize the same pitches across the octaves in the same way we can recognize a woman’s voice vs. a man’s voice.”

Dolphins process and recognize an amazing range of frequencies, from the ultra-low 16 herz to the high-frequency 150 herz. Pack says that dolphins use broadband clicks for echolocation. Narrow-band whistles, also called “signature whistles,” are thought to be unique to each dolphin and are typically used for social commentary.

“Dolphins will imitate the signature whistle of close companions. Mothers, when separated from young, may mimic their youngster’s signature whistle to call them, and close companions mimic each other when they’re separated.”

Frog filters

At the other end of the size spectrum, sound frequency also appears to be a critical element in frog and even insect communication. Frogs have developed the ability to filter the distinct frequencies and rhythms of their own species’ calls through a thick curtain of background sounds in a jungle.

“Frogs can also `time share’ the spacings of their calls to an amazing degree,” says Peter Narins, a leading neural ethologist based at the University of California Los Angeles. “Some frogs care about the frequency of a call, others about the timing.”

Crickets are even more efficient — each species produces sound at only one frequency. The females of the species can hear only that frequency, which tends to be right around 5,000 herz, says Kenneth Prestwich, a biologist at the College of the Holy Cross.

Like birds and whales, frogs and crickets have only one or two things in mind when they’re creating those pleasing calls. “There’s no question that frog calls can be melodious. You can’t help but notice that when you’re in the rain forest,” says Narins. “The sounds are beautiful and melodic and can be everything that music is, but it isn’t an artificial score.”

And that’s the distinction. While animals are using their melodic sounds to communicate basic needs, humans are able to use music for that and more. “The elements of music are in our communication,” Eisner says, noting that pitch and rhythm are indeed formal musical elements, elements which also exist in the communication of songbirds, whales and even frogs.

The question is whether animals have taken communication a step further to make music. At this point, Eisner and most other scientists believe that music-making, that is, creating and forming sounds in a choreographed way, belongs to humans alone.

Knowing what researchers have uncovered about bird song, it’s unlikely that Mozart knew what his starling was really saying. But it was music to his ears nonetheless.