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song birds cling strongly to tradition. Most of the species sing the same tune for decades, mimicking the trills that they are effective to defend territory and attract females. In some cases, their songs are repeated from generation to generation for over a thousand years.
however, a team of researchers has traced how a new and rare song sparrow has become “viral” in Canada, travelling more than 3,000 miles from British Columbia to central Ontario between the years 2000 and 2019 and deleting a song is historical in the process.
The study, published in the journal “Current Biology” reports that sparrows white throated have abandoned their traditional song of three notes in favor of a single variant of two notes, although the researchers still do not explain the reason.
“as far as we know, is unprecedented,” says lead author Ken Otter, professor of biology at the University of Northern British Columbia. “We know of no other study that has seen this kind of spread through the cultural evolution of a type of song,” he says. Although it is well known that some species of birds change their songs over time, these developments cultural tend to remain in the local populations, becoming regional dialects in place of the norm for the species.
step to the two notes
In the 1960s, sparrows white throated all over the country whistled to a song that ended up on three notes, but when Otter moved to western Canada in the late 1990’s and began to listen to the songs of local birds, the endings were of two notes. “When I moved to British Columbia, they sang something atypical of what was the classical song sparrow white throat throughout the eastern Canada,” he recalls. Over 40 years, the songs that ended up on two notes, or songs that ended up in doublet, had become universal in the west of the Rocky Mountains.
Otter and his team used recordings of sparrows white throated uploaded onto the internet by fans of the observation of birds of North America to track the new song of double end. They discovered that the song was not only more popular in the west of the Rocky Mountains, but also was spreading rapidly through Canada beyond these populations of the west. “Originally, we measure the limits of dialect in 2004 and stopped in the middle of Alberta,” he says. “For 2014, every bird that we recorded in Alberta sang this dialect is western, and we begin to see it appear in populations as far away as Ontario, which is 3,000 miles away from us”.
Learning winter
The scientists had predicted that the grounds of wintering sparrows were playing a role in the rapid dissemination of the final two notes. “We know that birds sing in the wintering areas, so that the juvenile male can collect new types of songs if they spend the winter with birds from other areas of the dialect. This would allow the males to learn a new kind of song during the winter and take it when they return to the breeding sites, which helps to explain how it can spread,” explains Otter.
therefore, the researchers used sparrows with geolocators, what Otter called “small backpacks” to see if the sparrows were westerners who knew the new song could be shared terrain winter with eastern populations that then embrace it. They found that they did. And not only it seemed that this strange song was spreading around the continent, from these lands of hibernation, but that was also replacing completely the historical end of the triple note that had persisted for so many decades, something almost unheard of in songbirds, male.
The taste of females
The team discovered that the new song did not give to the males a territorial advantage over the others, but you still want to explore whether females have a preference between the two songs. “In many previous studies, females tend to prefer the kind of song local”, pointing to Otter. “But in the sparrows of white throat, we may find a situation in which females really like the songs that are not typical in their environment. If that is the case, there is a great advantage to any male that can sing a new kind of song”.
Now, another new song has appeared on a population of sparrows westerners whose early dissemination may reflect the end of a double note. Otter and his team are excited to continue his work and to see how this song changes in real-time with the help of citizen scientists. “When you do that all these people contribute with their private recordings that they make when they watch birds, gives us a more complete picture of what is happening across the continent,” he says. “It allows us to do research that was never before possible.”
