Most bird species are slow to change their tune, preferring to stick with tried-and-true songs to defend territories and attract 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. The study, publishing July 2 in the journal Current Biology, reports that white-throated sparrows from British Columbia to central Ontario have ditched their traditional three-note-ending song in favour of a unique two-note-ending variant — although researchers still don’t know what made the new song so compelling.
“As far as we know, it’s unprecedented,” says senior author Ken Otter, a biology professor at the University of Northern British Columbia. “We don’t know of any other study that has ever seen this sort of spread through cultural evolution of a song type.” Although it’s well known that some bird species change their songs over time, these cultural evolutions tend to stay in local populations, becoming regional dialects rather than the norm for the species. This is how the two-note ending got its start.
In the 1960s, white-throated sparrows across the country whistled a song that ended in a repeated three-note triplet, but by the time Otter moved to western Canada in the late 1990s and began listening to the local bird songs, the new two-note ending had already invaded local sparrow populations. “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. MORE