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How a bird forgot its mother tongue

New research to be published next month reports that this European bird gradually lost the syntactical structure of its song over the last million years, as it colonized island after island. 

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The chaffinch's song loses syntactical structure the further out the birds are found on the mid-Atlantic archipelago.

Robert Lachlan/Duke University

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Each time the chaffinch arrives on a new island, it forgets its species’ traditional song a little more.

In the first instance of quantifying how bird songs change over time, new research reports that this European bird gradually lost the original syntactical structure of its song over the last million years, as it colonized island after island. Now, just the chaffinches in the bird’s ancestral homeland, mainland Europe, are fluent in the song, while the birds out on the last colonization stop, in the Canary Islands, sing an un-patterned version.

That the chaffinch’s loss of syntax followed such a neat, directional pattern suggests that the evolution of the chaffinch’s song is not random at all, but somehow yoked to the bird’s island hopping. That find also furnishes a new question: What about moving to a new island pressures a bird into unraveling its song? Answer that question, the authors say, and it might be possible to better clue into the process through which one species of bird becomes two species, and then four, and so on.

“We found this really striking pattern of evolution,” says Robert Lachlan, a postdoctoral fellow at Duke University and the lead author on the paper, to be published in October in the journal Current Biology.

“Something that happened during or shortly after the process of colonization was responsible for the change in song structure,” he said. “But we can’t say for sure what it is yet.”

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