White-throated sparrows in British Columbia are whistling a new song and it’s going viral across Canada.
What started as a minor change to a common song has now become a phenomenon across the continent before our own ears.
“As far as we know, it is unprecedented,” says biologist Ken Otter of the University of Northern British Columbia, Canada.
“We don’t know of any other study that has seen this type of spread through the cultural evolution of a type of song.”
When Otter moved to western Canada in the late 1990s, he heard white-throated sparrows (Zonotrichia albicollis) singing an unusual tune. Rather than sticking to the usual three-note finish of the species, local sparrow populations were finishing their tune on two notes.
https://www.youtube.com/watch?v=XJ98hPcRARE
Between 2000 and 2019, this little change has traveled more than 3,000 kilometers (1,800 miles) from British Columbia (BC) to central Ontario, practically erasing the end of a historical song that has been around since the 1950s at least.
No one knows what is so addictive about this new ending, or why it can’t exist along with the three-note variant, but scientists are trying to figure it out.
Thanks to citizen scientists, researchers were able to analyze the songs of 1,785 male white-throated sparrows, which were recorded from the 1950s onward.
While it’s not unusual for sparrow and other bird populations to change their tunes, it’s generally still a regional dialect. It certainly doesn’t extend like BC’s.
And yet, from Alberta, to Saskatchewan, to Manitoba, this unique ending crossed Canada’s prairie provinces in record time.
“It could very well be a ‘we haven’t noticed it before’,” Otter admits to ScienceAlert.
“Now that many more songs from vast areas are uploaded each year, it is possible to start exploring whether this is a more general phenomenon in other species.”
In 2004, data shows that Alberta’s sparrows were still threshing with the triplet ending in the species. Ten years later, all the males in that region had changed to a double.
By 2015, it had spread to central Ontario, completely supplanting the three notes ending in the northwest. By 2019, it had reached western Quebec, covering the entire western portion of the species’ geographic range.
In total, it is a linear distance of almost 3,300 kilometers.
“Within the regions where the double-ending song variant spread, it was also completely replaced in the process,” the authors write.
“As far as we know, this is an unprecedented rate of song type transition in any species of bird.”
Using citizen science databases such as eBird and Xeno-Canto, the new study shows that the songs heard on the winter grounds tend to coincide with the origin of the sparrows.
“This concentration and intermingling of birds from large portions of the breeding range suggests that the spread of song variants among populations may be facilitated by song tutoring in wintering locations,” the authors write.
Incidentally, there are reports that white-crowned sparrows (Z. leucophrys) sometimes incorporates elements of other dialects during winter singing.
To test this idea, the researchers associated geolocators, or what Otter calls ‘little backpacks,’ with 50 male sparrows in British Columbia. They then retrieved the devices after the animals had migrated, some to the west and some to the east.
Several crossed the Rocky Mountains and entered a new breeding region, which could have extended the new ending of the song to eastern populations.
“We know that birds sing in wintering places, so young males can pick up new types of songs if they overwinter with birds from other areas of the dialect,” says Otter.
“This would allow males to learn new types of songs in the winter and take them to new places when they return to breeding sites, which would help explain how the song type could spread.”
It is still unclear why men end up embracing this new ending. Otter says the ending could be simply compelling because it is unusual and unique. However, like many other bird songs, it might have to do with females and their preferences.
“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. ”
And it could be happening again. Researchers are currently seeing a new song variant that suddenly emerged in western sparrow populations and is rapidly spreading.
Maybe this time, we can find out why.
The study was published in Current biology.
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