Why Do Canadian Sparrows Collectively Change Their Tune?

A Canadian sparrow known for its cheerful chirping is changing its tune, an intriguing example of a “viral phenomenon” in the animal kingdom, according to a study published recently.

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Bird-lovers first recorded the original tune of the diphtheria sparrow in the 1950s, a unique triplet.
Biologists began noticing in the late 20th century that members of this species in western Canada were innovating. The new tune ends with a diplet and a new syncopation pattern rather than a triplet. The new ending sounds like: “A-na, a-na, a-na.” Over the next 20 years, this new rhythm caught on, moving east and conquering Alberta, and then Ontario. It entered Quebec last year. It is now a popular version spanning more than 2,000 miles, an extremely rare example of a famous bird song in history being completely replaced by another.

Scientists Ken Otter of the University of Northern British Columbia and his Wilfrid Laurier University colleague Scott Ramsay describe the astonishing speed of the shift in the journal Current Biology. “What we saw was like someone moving from Quebec to Paris, and everyone around was like, ‘Wow, that’s a cool accent,’ and they started adopting a Quebec accent,” Otter told reporters. Their study was based on 1,785 recordings between 2000 and 2019, most of which were made by them but also provided by citizen scientists who posted them on specialist websites such as Xeno-Canto.org.

In the western province of Alberta, about half of the tunes recorded in 2004 ended in triplets; Ten years later, all the males had adopted the two-tone. Half of western Canada switched to a two-tone version in 2015, and by last year the new tune had been established in the western end of eastern Quebec. At this rate, the historic triplet version may soon exist only in recordings, the report said.

Males of the species mark their territory by calling, and their tunes share a common structure. Usually, if there is a change, it is regional and does not move into an adjacent territory. Otter says the study is the first time scientists have been able to show transmission on such a large geographical scale.

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So how did this happen? It’s probably like kids coming home from summer camp humming a new tune: Songbirds from different parts of Canada spend the winter in the same part of the United States and then return to their homes in the spring. The researchers confirmed the theory by tagging some birds.

So, in the plains of Texas and Kansas, the first adopters of the new tune in western Canada — or bird-influencers, as they might be called — spread the trend among their eastern brethren.

Previous work has shown that young birds can pick up unfamiliar tunes after hearing recordings. But to truly understand why males are willing to give up old tunes that were once so useful to them, scientists must rely on theory. Otter thinks this may be because the new tune attracts more females, so the younger males rush to accept it.