Birds hardly change their tunes. And even when they do, it usually remains within the local populations and the changes become regional dialects.
But according to a recent study, over the last two decades, white-throated sparrows of British Columbia have actually devised a new tune, which has gone viral in the sparrow community of Canada.
These white-throated sparrows across western and central Canada have replaced their original three-note call with a two-note one.
Ken Otter, lead author of the study published on July 2 in 'Current Biology' says the original tune had triplet ending sounds like "Oh, my sweet Can-a-Da, Can-a-Da, Can-a-Da".
But now with its new two-note ending, it sounds more like 'Oh, my sweet Cana Cana Canada.'
Otter was actually one of those who first noticed a basic change in sparrow tune in the late 1990s. He noticed it when one of his colleagues in British Columbia mentioned that the sparrows sounded weird.
Some bird calls usually undergo slow evolutions. This kind of rapid shift in a bird's song had never been observed before. Otter mentioned that it is still a mystery how and why this song has spread like this.
Studies found that the new song originated in the west of the Rocky Mountains, and has been steadily and quickly spreading eastward. By 2014, every sparrow in Alberta area was singing the doublet song and every sparrow in the west of central Ontario was singing the new tune by 2015.
It did not stop there. It is still spreading in western Quebec, nearly 2,000 miles from where the new doublet tone originated.
Researchers speculate that young birds choose the new song and carry it to their mating grounds, from where the new tune spreads to other sparrows. Otter suspected that the eastern and western sparrows' crossing paths may have been playing a role behind it.
According to Otter, western sparrow population meets eastern populations in the southern Great Plains of the United States crossing the Rocky Mountains. This might have been a tutoring ground for young male sparrows to learn the new song before returning to their respective breeding ranges and spreading it further.
Otter and his team were able to map the song's spread using two decades of citizen-recorded data, including more than 1,785 recordings.
New bird calls emerge every now and then but they either eventually die out or remain as a local dialect. But somehow the sparrows have found this doublet tone interesting.
Why the new doublet tone is so compelling remains a mystery. There is no evidence that this new tune gives any advantage at wooing mates or defending territories.
Perhaps, the white-throated female sparrows prefer the songs that are not typical to their environment, says Otter.
If that is the case, then learning and singing new tune might come in as an advantage for the male sparrows.
Whatever the reason is, it seems that these sparrows have some of the best tunes.
However, the researchers have identified another new tune in Prince George, British Columbia.