Twenty-year-old study tracks a sparrow song that went ‘viral’ in Canada

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 a rare sparrow song went “viral” in Canada, traveling more than 3,000 kilometers between 2000 and 2019 and erasing a historical song that ends in the process. The study, published July 2 in the journal. Current biology, reports that white-throated sparrows from British Columbia to central Ontario have abandoned their traditional three-note song in favor of a single two-note variant, though researchers still don’t know what made the new song so compelling.

“As far as we know, it is unprecedented,” says lead author Ken Otter, a professor of biology at the University of Northern British Columbia. “We don’t know of any other study that has seen this type of spread through the cultural evolution of a type of song.” Although it is well known that some bird species change their songs over time, these cultural evolutions tend to remain in local populations, becoming regional dialects rather than the norm for the species. This is how the end of two notes started.

In the 1960s, white-throated sparrows across the country whistled a song that ended in a repeated three-note treble, but by the time Otter moved to western Canada in the late 1990s and began listening to the local bird songs, the new two Final Note had already invaded local sparrow populations. “When I first moved to Prince George in British Columbia, they were singing something out of the ordinary for the white-throated sparrow song across eastern Canada,” he says. Over 40 years, songs ending in two notes, or songs ending in doublet, had become universal west of the Rocky Mountains.

Otter and his team used the vast network of North American citizen bird watchers who had uploaded recordings of white-throated sparrow songs to online databases to track the new double-ended song. They found that the song was not only most popular west of the Rocky Mountains, but was also rapidly spreading across Canada beyond these western populations. “Originally, we measured the boundaries of the dialect in 2004 and halted half of Alberta,” he says. “By 2014, every bird we recorded in Alberta sang this western dialect, and we began to see it appear in populations as far away as Ontario, which is 3,000 kilometers from us.”

Scientists predicted that the sparrows’ hibernation grounds were playing a role in the rapid diffusion of the end of two notes. “We know that birds sing in wintering areas, so juvenile males can pick up new types of songs by wintering with birds from other areas of the dialect. This would allow males to learn new types of songs in the winter and take them to new places when they return to the playback locations, which helps explain how the song type can spread, “says Otter.

Therefore, the researchers used sparrows with geolocators, what Otter calls “little backpacks,” to see if western sparrows who knew the new song could share winter terrain with eastern populations who would later adopt it. They found that they did. And not only did this weird song seem to be spreading across the continent from these hibernation grounds, it was also completely replacing the historic triple-note ending that had persisted for so many decades, something almost unheard of in male songbirds.

Otter and his team discovered that the new song did not give male birds a territorial advantage over their male counterparts, but they still want to study whether female birds have a preference between the two songs. “In many previous studies, women tend to prefer the local song type,” says Otter. “But in white-throated sparrows, we might find a situation where women really like songs that are not typical in their environment. If that’s the case, there is a great advantage for any man who can sing a new type of song. “

Now, another new song has appeared in a population of western sparrows whose early release may reflect that of the double-note ending. Otter and his team are excited to continue their work and see how this song changes in real time with more help from citizen scientists. “By having all these people contribute their private recordings that they just do when they go birding, it gives us a much more complete picture of what is happening across the continent,” he says. “It allows us to do research that was never possible before.”