The Canadian white-throated sparrow once sang a delightful song that ended with three distinct repeated notes that rang out in a rhythm resembling Can-a-da, Can-a-da, Can-a-da.
But today, the Canadian White-throated sparrow ends its song with a triple, two-note ending that sounds like this: Can-a, Can-a, Can-a.
And that missing note sounds the beginning of one of avian science’s greatest mysteries – why has the Canadian white-throated sparrow (Zonotrichia albicollis) dropped its final note in the can?
This mystery begins more than two decades ago when ornithologists distinctly recorded the association between the Canadian white-throated sparrow and its three-note song ending.
However, around the year 2000 experts began to note that this signature tune was beginning to change, not everywhere and not in every bird but some birds were undeniably changing their tune.
Now, bird scientists around the world have previously accepted that bird songs do not usually change very much, if at all, in a local region. So, the discovery in 2000 was, scientists thought, an unusual blip.
But that was nothing to the findings of a study in 2014, which discovered that the change was not only taking precedence, it was roaring across the country’s white-throated sparrow population at a rate of knots with 22 per cent of males singing the new song. By 2017, half the male birds were singing it.
According to research data released by a team at the University of Northern British Columbia in Prince George, Canada, these changes were documented at a remote research station in eastern Canada and the latest findings are even more remarkable.
The study says new tune started in British Columbia and spread east and now most male white-throated sparrows have joined the choir. Moreover, it is still spreading in Quebec, more than 3,200 kilometres from the place it originated.
“When we first noticed the change, we thought it was specific to this one community of sparrows,” says Dr Ken Otter, an avian biologist and researcher at the University of Northern British Columbia.
“It wasn’t until seven or eight years later that we started to realize that the song was actually spreading eastwards.”
The problem is no-one knows for sure why the birds have changed their song, not even Dr Otter. He suspects that because males are the principal singers in the bird world, and that song is mostly about attracting the opposite sex for procreation, then the song and the change may be inextricably linked.
“If there is a little bit of female preference, which is something we want to test next, then it would be advantageous for males to sing an atypical song. And after a while, it would just take over,” Dr Otter says.
And you know what? That rings true – after all, love is the strongest force in nature, right?