Even if you’re not a bird person, you probably know the jaunty song of the white-throated sparrow. It plays on loop in North America’s boreal forests, a classic as familiar as the chickadee’s trill and the mourning dove’s dirge. It even has its own mnemonic, “Old Sam Peabody-Peabody-Peabody.”
But over the past half-century, the song’s hook — its triplet ending — has changed, replaced by a new, doublet-ended variant, according to a paper published Thursday in Current Biology. It seems the sparrows want to sing something new.
The study, which took 20 years, is “the first to track the cultural evolution of birdsong at the continental scale,” said Mason Youngblood, a doctoral candidate in animal behavior at the CUNY Graduate Center who was not involved in the research. It describes a much broader and more rapid shift in birdsong than was previously thought to occur.
Scott Ramsay, a behavioral ecologist at Wilfrid Laurier University in Ontario, was the first to notice that the forest sounded a little off during a visit to western Canada with Ken Otter, a professor at the University of Northern British Columbia.
“He said, ‘Your birds are singing something weird,’” Dr. Otter recalled.
Dr. Otter recorded some white-throated sparrow songs and turned them into spectrograms — visualizations that lay birdsongs out, so they can be more easily compared. The classic “Old Sam Peabody-Peabody-Peabody” songs ended in a triplet pattern: repeated sets of three notes. The new songs ended in doublets, like the record got stuck: “Old Sam Peabuh-Peabuh-Peabuh-Peabuh.”
It was “a different kind of syncopation pattern,” Dr. Otter said. “They were kind of stuttering it.”
Like many birds, male white-throated sparrows use songs to signal where their territory is, and to attract mates. Each individual sparrow has his own way of starting the song, but they all converge on a shared ending.
But as in the human world, those who mix novelty with familiarity occasionally find success, and their new song circulates through a particular community.
Usually, it stays there, and Dr. Otter and his colleagues figured this was happening only with their birds in western Canada, that “it was just an isolated, peripheral population” doing their own thing, he said.
When they tried to figure out where the song’s range ended, though, they realized birds were singing the song in other areas, too. In 2004, half the birds the researchers recorded in Alberta were singing doublets instead of triplets. By 2014, they all were, “and it was starting to show up as far east as Ontario,” Dr. Otter said.
To get a better sense of the spread, the researchers turned to citizen science birdsong databases. They pulled white-throated sparrow songs from across Canada and the northern United States, and plotted them over time and according to song type. In maps, you can see the doublet song gain prominence, its influence expanding and strengthening. By 2019, it had taken over completely from the Yukon to Ottawa, a certified hit that is currently encroaching on the Northeastern United States.
By tracking the western Canadian birds with geolocators, they found that some of them spend their winters in the southern United States, where they overlap with birds from other places. They’re probably sharing the song there, like a mixtape being passed around.
The possibility that the birds are swapping songs on their wintering grounds “really opens up how we think of song learning,” said Dana Moseley, an ecologist at James Madison University in Virginia who was not involved in the study. It’s also evidence that where birds “winter, where they stop over in migration, and where they breed shapes their behavior,” she said.
For a song to take off like this is highly unusual, said Dr. Otter. It goes against prevailing birdsong theories, which emphasize the benefits of sticking to your own local song type. What’s happening with the sparrows is “kind of like an Australian person coming to New York, and all the New Yorkers start suddenly deciding to adopt an Australian accent,” he said.
It’s unclear why the doublets are so popular. Dr. Otter and his colleagues think it has to do with the female sparrows, who may enjoy a little novelty.
Donald Kroodsma, a birdsong expert who was not involved in the study, agreed, pointing to previous work showing that certain populations of chestnut-sided warblers shuffle rapidly through songs that have to do with mating, while keeping fight songs mostly the same. “The speculations by the authors are appropriate, it would seem,” said Dr. Kroodsma. “But only the birds know.”