In just sixty years Alasania zonotrichia from Canada almost completely changed their repertoire. The traditional song with the ending of three notes came with new, which ends with two notes. As noted by the authors in the journal Current Biology, it originated in the West, and from there spread to the East. Such a rapid change are unique among birds. According to ornithologists, the reason could be the interest of females zonotrichia to the novelty — but the idea has not yet been confirmed.
The musical tastes of people are changing very fast. A new track could gain popularity just a few weeks, making everyone forget about the previous leaders of the charts. Against this background, the songs of birds seem to be incredibly stable, although they also gradually transformirovalsya in the course of cultural evolution, it is usually too slow a process so that an ordinary person could detect it.
However, there are exceptions. In the 1960-ies Alasania zonotrichia (Zonotrichia albicollis) across Canada sang a song which ends with a repeated fragment of three notes (usually its sound convey the English phrase “O-oh sweet Canada, Canada, Canada”). Half a century later, you can hear it only in the extreme East of the continent (or on older records, for example, in the video below). In the rest of the area birds completely abandoned the traditional songs in favour of a new option, with the final phrase of two notes.
A team of ornithologists under the direction of Ken Otter (Ken A. Otter) from the University of Northern British Columbia decided to find out why the repertoire of zonotrichia changed so quickly. First, they compared archived recordings of the songs of these birds, made in the last century, with samples 2000-2019 years. In total the collection included songs 1785 males.
Analysis of the records showed that song with the end of two notes originated in Western Canada in the middle of the last century, and then spread rapidly across the continent. To 2000-2004 year it completely replaced the traditional West of the Rockies, and several years later entered the Eastern part of Canada. In 2014 it was all males in the province of Alberta, and in 2015 — all males are to the West of the Central part of the province of Ontario. By 2019, Western reached Quebec. In just 60 years he traveled over three thousand kilometers, simultaneously displacing the original version of the song. According to the authors, such a rapid change of the repertoire is unique among birds.
Records from Algonquin provincial Park to the East of the province of Ontario has allowed to reconstruct in detail how the new version of the song replacing the old in a single location. Until 2000 all zonotrichia here sang a song with the ending of three notes. In 2005, she first entered the territory of the Park — it was performed by one male of seventy-six, whose voices were on the record. Nine years later, the popularity of the new version has grown to twenty-two percent, and three years later — almost to fifty. Thus, the growing popularity of “Western” songs is exponentially.
The authors suggested that the song with the end of the two notes is distributed through males who are just learning to sing. The wintering of young birds from Eastern populations occur from Western neighbors and caught from them a new version of the song. However, to confirm this hypothesis, it was necessary to prove that zonotrichia from different parts of Canada do winter in the same areas.
To do this, researchers marked geolocators 50 males from British Columbia, 20 in 2013 and 30 in 2016. It turned out that zonotrichia from Western Canada winter in two different areas: in California (this trip one of the nine males, geolocator which were returned) and in the South-Eastern United States (here spent the winter of the other eight). Southeast wintering use and birds from the Eastern populations. Because zonotrichia actively singing in non-breeding areas, the idea of the exchange of songs between individuals from different parts of the continent can be considered confirmed.
Unfortunately, scientists have not been able to figure out why the new version of the song almost completely replaced traditional. Perhaps the reason should be sought in the tastes of females zonotrichia who are very critical about the final phrase of the song. In the population, where the predominant traditional version, the alternative version may attract females of their novelty, which enhances its popularity among males. This idea of waiting until the check. Meanwhile, in the West of Canada has already distributed a new version of the song with different beginning of the final phrase.
Sometimes the repertoire of songbirds are changing under the influence of external circumstances. For example, yellow-headed forest songbird that lives in the Western United States, the songs become more varied after a forest fire. According to ornithologists, this is due to the fact that natural disasters make the birds more active to settle, with the result that the speakers of different dialects are mixed.
Sergey Knee High