Most bird species are slow to change their tune, preferring to stick with tried-and-true songs, which help in attracting the females. Now, with the help of citizen scientists, researchers have tracked how one rare sparrow song went “viral” across Canada, traveling over 3,000 kilometres between 2000 and 2019 and wiping out a historic song ending in the process.
“As far as we know, it’s unprecedented. We don’t know of any other study that has ever seen this sort of spread through cultural evolution of a song type,”
Senior author Ken Otter, a biology professor at the University of Northern British Columbia.
Although some bird species tend to change their tunes over time, there are some regional dialects amongst birds of a particular area which show cultural evolutions within species. This was how two note endings and three note endings have been concluded.
“When I first moved to Prince George in British Columbia, they were singing something atypical from what was the classic white-throated sparrow song across all of eastern Canada,” he says. Over the course of 40 years, songs ending in two notes, or doublet-ending songs, had become universal west of the Rocky Mountains.“
Ken Otter
With the help of a large network of citizen scientists, Otter had found that the song was not only popular to the west of the Rocky Mountains, but that it was also spreading rapidly across Canada, beyond the western populations. The dialect boundaries had stopped halfway through Alberta in 2004, but a decade later every bird in Alberta was singing this western dialect and it had been appearing in populations as far away as Ontario, which is 3,000 kilometers from their location.
So the researchers harnessed sparrows with geolocators—what Otter calls “tiny backpacks”—to see if western sparrows who knew the new song might share overwintering grounds with eastern populations that would later adopt it. They found that they did. And not only did it appear that this rare song was spreading across the continent from these overwintering grounds, but it was also completely replacing the historic triple-note ending that had persisted for so many decades—something almost unheard of in male songbirds.
But through the study, they found that the new song didn’t give male birds a territorial advantage over their counterparts, but still want to study whether female birds have a preference between the two songs.
“In many previous studies, the females tend to prefer whatever the local song type is. But in white-throated sparrows, we might find a situation in which the females actually like songs that aren’t typical in their environment. If that’s the case, there’s a big advantage to any male who can sing a new song type.”
Ken Otter
Now, another new song has appeared in a western sparrow population whose early spread may mirror that of the doublet-note ending. The team is very excited to continue their work and see how this song shifts in real time with more help from citizen scientists.