Birds Sing to a Different Tune
It's not just humans who have different accents and dialects. It turns out, song birds do, too. Like humans, they have different dialects that depend on where they live. Song birds also learn their songs - much the same way humans do. Scientists from Ohio State University are researching the song-learning process and influence of dialects on behavior.
That was the song of a white-crowned sparrow. The trained ear would also know the song was of a certain dialect, from near Bandon, OR, about 100 miles from the California border. OSU biology professor Douglas Nelson has such a trained ear. He studies songs of white-crowned sparrows. He's found that, unlike other birds or noise-making animals like frogs, song birds learn their songs over time.
"What makes it interesting to us is that birds learn their songs, so there's some similarities in that respect to how humans develop their own speech," Nelson says.
He says this might be the only animal model scientists have for this type of speech learning. The research may have implications for neurobiology.
"There's a lot of interest from neurobiologists in the brain mechanisms involved in this learning process so that's a very active area of research and a lot of important discoveries have come out from the bird song research," says Nelson.
Bird songs have dialects the same way human languages do. Tiny differences in song accumulate over time and become distinct dialects. Two white-crowned sparrows less than 70 miles apart may have different dialects.
Nelson says the white-crowned sparrow is possibly the most well-researched bird. He says the sparrow, which is native to the Pacific Northwest, provides a textbook example of song-learning. The researchers have already found that white-crowned sparrows can distinguish dialects. From playing back song recordings for the birds, they discovered that the sparrows respond more strongly to their own dialects.
A particular dialect is characterized by how a song ends.
"It appears that the main difference between these dialects up and down the Pacific Northwest coast is in the ending of the songs, what we call the trill," Nelson says.
Nelson says it's fairly easy for the human ear to identify dialects. One of the dialects of white-crowned sparrows from Puget Sound in Washington has a slower trill. A second, neighboring dialect has a faster trill.
Nelson and a post-doctoral researcher, Angelika Poesel, have just returned from this season's field work in Oregon. They're trying to find just what kind of effects dialects may have on behavior. From March through June, they slept in tents along the Pacific Coast where the sparrows live. They recorded songs, noted behaviors, and took blood samples. They're in their second year of a four-year study to determine how dialects influence territorial and mating behavior of males.
So we're interested in whether these dialects or whether having a song that's similar to what your neighbor is singing whether that's important to males both in defending territory with other males, and also in the context possibly of mate choice.
Nelson says nearly all songbirds have dialects. But the white-crowned sparrow is easier to study because it only has one type of song. Other songbirds, like the cardinals that are native to Ohio, have six to ten song types.
Nelson is also the Director of the Borror Laboratory of Bioacoustics at OSU. The laboratory has a sound database not only of birds, but also insects, frogs, and toads. They have over 30,000 recordings of over 1400 different animals for scientific and public use.