World Teach Laura Molles is so attuned to birds that she can tell where birds of some species are from just by listening to their song. She’s not a real-world Dr Doolittle. She’s an ecologist in Christchurch, New Zealand, who specializes in a little-known area of science: bird dialects. While some birds are born knowing how to sing innately, many need to be taught how to sing by adults — just like humans.
Those birds can develop regional dialects, meaning their songs sound slightly different depending on where they live. Think Boston and Georgia accents, but for birds. Just as speaking the local language can make it easier for humans to fit in, speaking the local bird dialect can increase a bird’s chances of finding a mate. And, more ominously, just as human dialects can sometimes disappear as the world globalizes, bird dialects can be shaped or lost as cities grow. The similarities between human language and bird song aren’t lost on Molles — or on her fellow bird dialect experts. “There are wonderful parallels,” said American ornithologist Donald Kroodsma, the author of “Birdsong for the Curious Naturalist: Your Guide to Listening.” “Culture, oral traditions — it’s all the same.”
The first bird dialect experts For centuries, bird song has inspired poets and musicians, but it wasn’t until the 1950s that scientists really started paying attention to bird dialects. One of the pioneers of the field was a British-born behaviorist named Peter Marler, who became interested in the subject when he noticed that chaffinchesin the United Kingdom sounded different from valley to valley. At first, he transcribed bird songs by hand, according to a profile of him in a Rockefeller University publication. Later, he used a sonagram, which Kroodsma describes on his website as “a musical score for birdsong.” (“You really need to see these songs to believe them, our eyes are so much better than our ears,” Kroodsma said.)
In the 60s and 70s, scientists put baby birds into sound isolation chambers to see if they would be able to sing their songs, according to ornithologist David Luther. Scientists found that some birds — the ones that learn their songs — couldn’t sing at all. “They just continued like a baby babble for their entire life,” he said. Those birds are known as “true song birds.” In other birds, singing was innate. “When they came of age they could just sing a perfect song no problem.”
When birds are copying adults, scientists discovered, they sometimes make a mistake. That mistake in turn is copied by other birds, and a local dialect develops. That means that dialects can only exist in true song birds because they have a “learned oral tradition,” says Kroodsma. Dialects can also be created as birds adapt to the local environment, said American ornithologist Elizabeth Derryberry. Birds that can be heard better may find a mate better, meaning their song is more likely to be handed down from generation to generation.
It relates to an idea developed by Bernie Krause, the founder of soundscape ecology, that animals make sounds at different pitches so they can all be heard. Some dialects shift fast — even within a breeding season. Other birds hold on to their dialects for decades. When Luther researched San Francisco dialects of white-crowned sparrows — a common bird in North America — he found that some dialects hadn’t changed at all in 40 years. Dialects and dating (in birds)
For something that is often the result of a copying glitch, dialects can be very useful. According to Molles, birds communicate for two reasons: Either they are trying to tell off their neighbor, or they are trying to attract females. “Nothing very poetic, unfortunately,” she quips. When it comes to defending territory from other birds of the same species who aren’t local to the area, knowing the local dialect allows for more complex interaction. Mimicking a song note for note is seen as aggressive to birds, so having a wider repertoire means a bird can get its point across without escalating the interaction to a fight. Knowing the local dialect is also useful when it comes to finding a romantic partner. In many species, it’s the male who does the singing.
According to Molles, females tend to prefer a familiar dialect — it suggests the male birds know the local area, has territory, and isn’t just “someone who’s passing through.” Some birds are bilingual, or even trilingual — perhaps because they have grown up around different local dialects. When they are mating, they’ll opt to sing the local dialect of wherever they choose to settle, Luther said. But not having the right dialect isn’t an insurmountable barrier. Kroodsma gave the example of a prairie warbler in Massachusetts, where he is based, which has returned every year for the past few years. Although the bird has a very atypical song, it attracted females and raised babies every year.