"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."
Canada's Sparrows Are Singing a New Song. You'll Hear It Soon. https://nyti.ms/2VGVHNL
Jamie:
My cynical hunch was that the novelty of the doublet ending and the sole source of Northern BC of such were both over-stated.
The paper is available online as is a seminal one from 1965 which it briefly references to say triplets were ubiquitous.
The new paper clearly shows a trend in doublets heading East which must be as they claim cultural transmission - very cool.
But the latter paper from 1965 actually states "Six of the 433 recorded birds (1.4 per cent) sang a song that ended in doublets instead of triplets: 1 from Quebec ... 2 from Maine ... 2 from Ontario ... and 1 from Manitoba... The occurrence of this feature in Whitethroat songs is thus not restricted to western birds, as Saunders (1935: 270) suggested."
So there is more to it as always. I wonder if noise pollution might also play a role on their shared wintering grounds. Or perhaps more and more Western birds gradually showing up in the East due to increasingly differential mortality (caused by us humans no doubt).
TE: It's really interesting. I didn't realize how many decades this has been studied.
Here's a study confirming what you suspected, that urban noise pollution is affecting the White-crowned songs.
"Urban noise, which is louder at low frequencies, increased during our study period and therefore should have created a selection pressure for songs with higher frequencies. We found that the minimum frequency of songs increased both within and between dialects during the 30-year time span."
And this intriguing study that males share more varied songs with their nearest neighbors than distant visitors.
"Machine learning song analysis methods allow us to overcome perceptual bias in the classification of the songs of New Zealand hihi (Notiomystis cincta). We show that males share more song elements of their repertoire with their neighbors than with more distant males or with males from the same natal area."
And here's a lovely homespun warm ode to the variations in song and appearance of the song sparrow.
And isn't the Ipswich sparrow just a pale variant of the Savannah sparrow?
Mitochondrial DNA Variation, Species Limits, and Rapid Evolution of Plumage Coloration and Size in the Savannah Sparrow.
"haplotypes found on Sable Island representing the "Ipswich sparrow" were not distinctive, thereby failing to support species status for this taxon."
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