White-throated sparrows are changing their tune — an unprecedented development scientists say has caused them to sit up and take note.
Ken Otter, a biology professor at the University of Northern British Columbia, whose paper on the phenomenon was published on Thursday, said most bird species are slow to change their songs, preferring to stick with tried-and-true tunes to defend territories and attract females.
But the shift to this new tune went viral across Canada, travelling over 3,000 kilometres between 2000 and 2019 and wiping out a historic song ending in the process, he said.
"The song is always described as being 'Oh My Sweet Canada Canada Canada Canada — so that Canada is three syllables. It's a da-da-da, da-da-da, da-da-da, da-da-da sound. That's the traditional description of the song going back into early 1900s," Otter said in an interview Wednesday.
But now, the song has changed.
"The doublet sounds like Oh My Sweet Cana-Cana-Cana-da. They are stuttering and repeating the first two syllables and they are doing it very rapidly. It sounds very different."
From British Columbia to central Ontario, these native birds have ditched their traditional three-note-ending song for a two-note-ending variant, he said, adding researchers still don't know what has made the new tune so compelling.
Otter drew a comparison to people picking up the accent, phrases and pneumonics of a new area they move into.
"This is actually the opposite," he said.
Male sparrows are showing up singing atypical songs but then others are starting to adopt that, and over time the dialect is actually changing within that site to the new type and replacing the old tune, he said.
"So it's like somebody from Australia arriving in Toronto and people saying, 'hey, that sounds really cool,' mimicking an Australian accent and then after 10 years everybody in Toronto has an Australian accent," he said.
"That's why, at least within the scientific community, it's getting so much interest. It is completely atypical to what you would predict around all the theories that you have about dialects."
Otter and a team of citizen scientists have found that the new tune is not just more popular west of the Rocky Mountains, but was also spreading rapidly across Canada.
"Originally, we measured the dialect boundaries in 2004 and it stopped about halfway through Alberta," he said in a news release.
"By 2014, every bird we recorded in Alberta was singing this western dialect, and we started to see it appearing in populations as far away as Ontario, which is 3,000 kilometres from us."
The scientists predicted that the sparrows' overwintering grounds were playing a role in the rapid spread of the two-note ending, he said.
Scientists believed that juvenile males may be able to pick up new song types if they overwinter with birds from other dialect areas, and take them to new locations when they return to breeding grounds, which could explain the spread, he said.
So they fitted the birds with geolocators — what Otter called "tiny backpacks" — to see if western sparrows that knew the new song might share overwintering grounds with eastern populations that would later adopt it.
"They found that they did," he said in the release.
Otter said he does not know what has caused the change, and his team found that the new song didn't give male birds a territorial advantage over others.
"In many previous studies, the females tend to prefer whatever the local song type is," he said.
"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."
The new song can be chalked up to evolution, he said in the interview.
Otter said he prefers the two-note song because it sounds smoother.
"But I'm not a sparrow so it doesn't really matter which one I prefer," he said with a laugh.
But the tune may be continuing to change, he said adding scientists were supposed to study it this year but COVID-19 has put a damper on the field season.
"The two note is not the be all and end all because in the last five years we noticed a male that was singing something slightly different than the standard two note doublet song," Otter said.
"And when we recorded it we noticed he was modifying the amplitude of the first note. And more of them are doing it now. We could be seeing waves of these things that we just never noticed before."