I was editing a piece the other day on mourning warbler songs, and learned that males who live in different parts of the country sing differently. The variations might sound subtle to you and me, but to a bird they’re probably quite stark. Researcher Jay Pitocchelli, an ornithologist at Saint Anselm College in New Hampshire, found that males in Newfoundland used 22 different syllables in their songs, while birds on the mainland used 110.
I guess another way to put this is that the birds have regional accents, making them like us, or us like them. The biggest differences occur when natural barriers of significant size prevent contact between varying populations: think the difference between Irish and English accents, or English and American, or American and Australian.
But, of course, things don’t have to be so dramatic. Pitocchelli notes that factors like land development also play a role in song divergence. A different study done in the boreal forest region in Canada found that habitat fragmentation altered black-capped chickadee songs in localized populations. A human equivalent might be the difference between the south Boston accent and the Massachusetts accent found just an hour drive outside of the city.
Another example might be the Catskill accent versus the downstate accent, which is the subject of a paper by Julian Rauter that recently showed up in my inbox. Rauter grew up in the Catskills and is studying language documentation and revitalization as an undergrad at Harvard. In his experiment he recorded 10-second snippets of sound from 10 “native” speakers (natives being defined as those having spent their first 18 years living in the Catskills) and 10 “migrant” speakers (those who spent their formative years downstate before moving to the Catskills). He then had a different set of people rate the accents. In over 60 percent of the cases, the raters correctly identified the migrants as “definitely not Catskill.” The flip side, of course, is that in 33 percent of the cases, migrants sounded “more Catskill,” an indication, perhaps, that they’d linguistically assimilated.
In this paper on warblers Pitocchelli writes: “Geographic variation in song may reduce or eliminate the ability of some populations to recognize each other as conspecifics, possibly leading to assortative mating, reproductive isolation, and speciation." In Rauter's paper on Catskill regiolects, he credits the 60-plus percent who didn’t assimilate, in part, to the social divide between natives and those from away. “Many downstaters reported experiencing difficulty becoming part of the community once they decided to become full-time residents of the Catskill region,” he wrote. “Very few migrants have a large volume of verbal interaction with natives.”
It’s just sort of interesting to see the parallels.