Stereotypes about city-dwellers abound. They’re always rushing. They’re curt. They’re shrill. A new study on birdsongs in urban areas suggests that birds might use some of the same tricks to cope with the challenges of urban life.

The study, which will be published in the December 5 issue of Current Biology, focuses on the great tit (Parus major), a small songbird common in Europe and Asia. Researchers recorded samples of the bird’s songs in ten European cities, including Paris, London, Prague, and Brussels, and compared each to songs in neighboring rural areas.

What they found was remarkable: In every comparison, songs in urban areas were significantly shorter and faster than those in rural areas. Researchers also noticed that  urban songs were higher in pitch, a finding that indicates that great tits have figured out how to make themselves heard over the low-frequency din of traffic.

The study is significant because it suggests natural selection: Great tits, which use their songs to attract mates, have evolved to excel in cities. Although the bird does not live in the United States, it is very closely related to one of the most common urban birds in America, the chickadee.

“If the great tit didn’t adapt, it might have less reproductive success,” says Hans Slabbekoorn, a behavioral biologist at Leiden University in the Netherlands and one of the study’s lead researchers. “This suggests that they are urban survivors.”

Previous research has shown that urban birdsongs are different from rural ones, but this study shows how birds modify their songs, says Stephen Yezerinac, a biologist at Bishops University in Sherbrooke, Quebec who  was not involved in the study.

“It’s like a change of vocabulary, as opposed to a change of pronunciation,” says Yezerinac, who has studied urban birdsongs in North America. “The birds were actually singing different songs, rather than just pronouncing the songs differently.”

While great tits, chickadees, sparrows, and pigeons might be able to adjust to life in cities, not all birds are so adaptable. Urban environments generally have far fewer species of birds than rural ones do.

“We know that wood larks and orioles are not common in the city any more,” says Slabbekoorn. “In old times, they were, and they have relatively low frequency sounds.” But, he adds, these birds have very specific habitat needs, and it’s unlikely that noise alone forced them out of urban environments.

Reed Bowman, director of the Avian Ecology Lab at Archbold Biological Station in Florida, says he believes the study is evidence of natural selection. But figuring out the order in which different traits develop is tricky.

“Some birds adjust their songs to the city, and others don’t,” he says. “But is it simply because some birds are there long enough for natural selection to take place?”

It will take more research for biologists to find out. If it does turn out that noise is driving some of the less adaptable birds out of the city, Slabbekoorn hopes that humans will notice and take steps to make cities quieter for the sake of birds—and people.

“Luckily for the birds, noise also bothers us humans,” he says. “So people are becoming more and more interested in how to deal with this.”

Posted on Dec 5, 2006 at 5:45 PM
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