Most birds have distinct calls that tend to stay the same. It’s how birders can recognize a species without seeing it. But new research shows these tunes can change.
Over the course of two decades, white-throated sparrows across western and central Canada have changed one of their songs, replacing a three-note call with a two-note one. The new tune started in British Columbia and spread east—now, most of Canada’s birds are singing it. And it’s still spreading in Quebec, more than 2,000 miles from where it originated.
Although some bird calls undergo slow evolutions, this rapid shift in a bird’s song has never been observed before, says Ken Otter, lead author of the study, published July 2 in the journal Current Biology.
“There is nothing that we know of that’s spread like this,” Otter says.
As the song sweeps west to east, ornithologists wonder what makes the song so catchy—and if the trend will continue. The finding was made possible by crowd-sourced birdsong recordings, which are uncovering patterns that may have previously gone unnoticed.