Canadian sparrows have changed their tune

Researchers in Canada have found that there’s a new hit song sweeping the country - at least among the nation’s white-throated sparrows. When biology professor Ken - another Ken - Otter moved to British Columbia in Western Canada he was surprised to discover that these small and noisy birds were singing a very different tune to their East coast colleagues. And as the years went by, recordings sent in from citizen scientists all over Canada showed that this west coast new song had gone viral! Eva Higginbotham spoke to Ken to find out more...

Ken - What it is is at the beginning of the song, the males have an introduction that has three whistled notes; very clean, pure-sounding notes. And it's supposed to... it's very patriotic in Canada, at least the description of it is that they're supposed to be singing, "my oh my, sweet Canada, Canada, Canada, Canada". And so that ending phrase is a repeat of three repeating notes with a little gap in between them. So it's "da-da-da, da-da-da, da-da-da," like that. And the males will sing that a variable number of times. That's the classic triplet ending song.

Eva - And you've actually sent me some recordings of that. So let's have a listen and hear what that sounds like, the triplet.

[BIRDSONG]

Eva - Okay. So I can hear the Canada, Canada, Canada. That's the classic - what's the new one?

Ken - That's the classic. The one that we found: instead of singing three notes, they sing two notes; it's kind of a long note-short note, long note-short note, with not much of a space in between it. And then they ended on a long note. So it kind of goes, "can-a can-a can-a can-a Canada," like that. So it's like they're stuttering the whole way through it.

Eva - Okay, cool. Let's give that one a listen too.

[BIRDSONG]

Eva - Uhuh, okay. So the song seems to have originated in the west of Canada and now is traveling east?

Ken - It was still the common song type in the east, across the eastern range of the birds, was the triplet ending songs in the early 2000s. And between 2000 and 2019, the doublet ending song spread across Canada and took over; it completely replaced the triplet ending song. So it's travelling across the country at quite a rapid pace and it's completely replacing the triplet song wherever it's taken a foothold. What was happening is our birds, in British Columbia, were overwintering with birds that were singing a totally different song type. And we started to look to see whether there was a possibility that the birds were singing on these wintering grounds and potentially serving as tutors for juvenile birds that bred and other populations. And that could explain how the song actually spreads from one population to another.

Eva - And so this was essentially a mixing of birds from the west of Canada with the east of Canada. They all head down and mix up and overwinter together.

Ken - That's basically what we found, that the birds do sing on their wintering ground, and we started to see this western dialect popping up in the eastern wintering grounds. But what's strange about this is that we're having situations where males are coming in and they're singing this new song type, the doublet ending song, and instead of converging on the common song type in a particular area, these few males that are settling suddenly become the template, and other males start adopting that song and it starts to spread in the population. And so the new song type starts to take over. It would be kind of like an Australian person coming to Cambridge and everybody suddenly adopting an Australian accent, and everybody starting to sound like Australians in Cambridge. And that's essentially what we're seeing here.

Eva - So what is special about the doublet sound that has made it take off so well?

Ken - I don't know specifically what it is about the doublet. It may just be that it's slightly different. And there are certain templates inside the bird's head that when they actually hit on that new song, it's acceptable, but it's novel. And that's what we think might be driving this: that they're picking it up just because it sounds slightly atypical, but it's still within the acceptable limits of what the birds recognise as an acceptable song. And so occasionally these things might pop up, and then if they're broadly adopted, then it just sweeps through the population quickly.

Eva - So it's sort of the cool new tune, which is not so far out that the birds will be put off by it, but it's different enough to sound cool and interesting.

Ken - Exactly. And so that's what we think might be happening. Because there doesn't seem to be a big disadvantage to sing one of these new dialects if you're trying to establish yourself as a territorial male. So we think what might be happening is that the females might actually like these slightly atypical songs, and that could be driving males to adopt them. But that's something that we still have to test.