If you consider Chirpy Chirpy Cheep Cheep to be the ultimate catchy tune, think again: British Columbia’s White-throated Sparrows have come up with a new song that has gone viral in Canada.
For years, the traditional descending whistle of the little songbird featured a three-note ending. But researchers have traced how a single two-note version of the male bird’s call has quickly spread 3,000 km (1,864 miles) east from western Canada to central Ontario during this century.
Many bird species are known to change their songs over time, but these “cultural” evolutions generally remain within local populations, becoming a regional “dialect” rather than the new normal for an entire species. Scientists have not previously observed how a new song dialect moves rapidly across a continent.
“As far as we know, it is unprecedented,” said Ken Otter, a biology professor 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.”
In the 1960s, white-throated sparrows across the country whistled a song that ended in a repeated three-note treble. When Otter moved to western Canada in the late 1990s, he noted that a new two-note ending had developed among local sparrow populations.
“When I 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 said. Over 40 years, songs ending in two notes, also known as double endings, had become a universal west of the Rocky Mountains.
Otter and his team used 18,000 recordings of male songs collected by citizen birdwatchers across North America to track the new double-ending song. Their study, published in Current Biology, found that in 2004, the two-note dialect stopped in the middle of Alberta. Ten years later, every recorded bird in Alberta sang the “western” dialect and began to appear in populations in Ontario, 3,000 km to the east.
Scientists predicted that young male birds would hear the new song when they shared the wintering grounds with birds from other areas of the dialect. The juveniles would then return to their breeding grounds singing the new song, extending it further.
The sparrows were equipped with geolocators that confirmed that those from the western regions were sharing hibernation grounds with eastern singers, who then returned to their eastern bases with the new tune.
Investigators are still unsure why the new song is so compelling. They found that it did not give males a territorial advantage over other males, but now they want to study whether females prefer the new tune.
“In many previous studies, women tend to prefer the local song type,” said Otter. “But in white-throated sparrows, we might find a situation where females 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. “
The bird was hailed for its patriotism in Canada, with its triplet ending song popularly described as “Oh My Sweet Can-a-Da, Can-a-Da, Can-a-Da”. “Unfortunately, this is being replaced with our western variant that seems to stutter birds ‘Oh My Sweet Can-a, Can-a, Can-a, Can-a-Da,'” Otter said.
Whatever the reason, the Wild West White-throated Sparrows seem to have the best tunes: Researchers have identified yet another new song in the Western Male Sparrow repertoire that in its initial extension may coincide with the ending double note movement.
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