White-throated sparrows singing a new tune

From the Beatles to Beyoncé,  the musical world is filled with groundbreaking artists who come along to shake up the game and change the way music sounds. It turns out the bird world may not be so different. Canadian white-throated sparrows were historically known for singing a patriotic song that sounds like they are calling, “Oh, sweet Can-a-da Can-a-da Can-a-da!”.

The three-syllable ‘Canada’ ending is now being unanimously thrown out the door: white-throated sparrows are instead singing a doublet-song ending that first popped up in British Columbia prior to the year 2000 before spreading across the country. The rapid takeover of this new tune from the west coast of Canada all the way to Ontario and Quebec shows an unprecedented rate of spread for a song variation, allowing researchers to use this phenomenon to study the cultural evolution of bird song.

“We started off looking at the song as a sort of curious regional dialect, that we initially thought had arisen because the population west of the Rockies is isolated from the main population to the east of the Rockies,” says Ken Otter, lead author of the study and Professor of Biology at the University of Northern British Columbia. 

But this unique song began to catch on with white-throated sparrows outside of this thought-to-be isolated population. Two decades of recordings of white-throated sparrows collected by researchers and citizen scientists showed that the new song spread like wildfire across the continent, replacing the old triplet-song.  In Algonquin Park, all white-throated sparrows sang the triplet-ending song until 2005, when a single male was caught singing the doublet-ending. By 2017, almost 50 percent of males in the park were singing the new tune. The new song reached into western Quebec in 2019.

Male white-throated sparrows sing to communicate two main messages to other members of their species. They sing to let other males know that a territory is occupied, and at the same time, “females hearing that song will know that there is a territory occupied by a male who is looking for a mate,” says Otter.

Dialects form because birds normally learn and sing the song that’s common to their region. “There’s supposed to be a big advantage to conforming to what your local dialect is,” says Otter. It increases the prospects of being able to communicate with neighbouring males, he says, and there’s a number of studies in various species showing that female birds prefer local dialects as opposed to foreign dialects.

Turns out that white-throated sparrows from across Canada do get a chance to hear each other’s unique tunes. Geolocation tracking revealed that white-throated sparrow populations from east and west of the Rockies meet and mingle on their winter grounds in the United States. This exposes juvenile males to different dialects of birdsong. 

During the first year of a bird’s life, they are very sensitive to listening to the songs that other males in their species are singing, says Otter. “They go through a memorization phase,” says Otter, where the males listen and learn the tonality of all the different songs they’re hearing. 

In late winter, prior to heading to their breeding areas, males go through a ‘subsong’ period, where males will try and sing the songs that are in their head, practicing and practicing their renditions until it becomes crystallized. Just like you might not remember all the lyrics to a song despite hearing them over and over again on the radio, Otter says that the young males might make some mistakes and warble around until they can sing their tune properly.

While the odd male may return to the breeding ground with a couple of changed notes in their song, it was unprecedented for a new song to increase in popularity and then begin to completely replace the old song so rapidly. Such a switchover suggests that males might be preferentially adopting these new song elements because there is an adaptive advantage to singing the doublet ending. 

Otter and his team tested if the new doublet-ending song affected a male bird’s ability to hold territory. They played both versions of songs to male sparrows  and found that the males treated both song dialects the same. “There’s no disadvantage to the male to sing a foreign dialect,” says Otter.

If the new doublet ending doesn’t make a difference in males coveting territory, that leaves open the possibility that female birds are driving males to sing a new song. Otter cites work by Jill Trainer in the 1980s that showed that male cacique birds in Central America changed their songs from the start of the breeding season to the end. Trainer suggested that the female caciques were becoming habituated to the old song type. “When the males introduced something new, it got the females attention again,” says Otter. Whether this is the case for white-throated sparrows remains to be tested.

The recordings of bird song by Otter and his team were collected in part by citizen scientists. Gone are the days where bird-watchers put pen to paper to create simple lists of species sightings. Now, online platforms such as eBird and xeno-canto allow birders to upload recordings of bird sounds from all over the world into a global sound library. 

These platforms allow scientists to enlist a thousand research assistants from all over the globe, says Otter. The information provided by citizen scientists is fuelling research projects that wouldn’t have been possible even ten years ago, and provide snapshots of what is happening to bird songs on an annual basis over a very broad geographic range. No fancy sound equipment is required to join this digital revolution, as smartphones are powerful enough to take research-quality clips of bird songs. So if you enjoy sipping your morning coffee on your cottage porch while listening to birds, take the time to record some of the the avian chatter. Who know: you might stumble upon the latest trend-setter in the world of birdsong. 

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