WILD NEIGHBORS: Not Just the Same Old Song

By Joe Eaton
Thursday April 26, 2012 - 05:01:00 PM
A semi-local (Half Moon Bay) white-crowned sparrow
Dick Daniels, via Wikimedia Commons
A semi-local (Half Moon Bay) white-crowned sparrow

From a birthday card I saw a couple of years ago: “It’s not that you’re getting older—the music really does suck.” 

I’m not going to take that one on, except to note that a lot of what I liked in the Sixties is pretty near unlistenable now. Music changes; context changes; tastes change. And that’s not just a human phenomenon. It’s been known for some time that hump-backed whales are susceptible to musical fads. All the males produce the same sequence of groans, whines, and gurgles until some innovator comes up with something new, which spreads worldwide and displaces the old song. 

That apparently happens among songbirds as well; those that learn their songs, at least. Song pattern is hardwired in some birds. You can expose a male olive-sided flycatcher to all kinds of influences in all stages of development, and it’s never going to say anything but “Quick, three beers!” This seems to be true of most of the suboscine passerines (tyrant flycatchers and a number of tropical families), which lack the vocal apparatus necessary for complex song. 

Most passerines—and a few nonpasserines, including some hummingbirds—are learners. They can only acquire “normal” song if they’re exposed to a model—a parent or neighbor—at a critical point in development. Scientists like Don Kroodsma have documented this with painstaking experiments involving rearing young birds in isolation and/or letting them hear only the songs of other species. 

Field research remains essential to understanding the song-learning process, though. The Bay Area has been a focal point for this kind of research, starting with the late Luis Baptista of the California Academy of Sciences and his studies of the white-crowned sparrow. Among other things, Baptista found that sparrows in different parts of San Francisco and the East Bay have developed distinctive local song dialects—three in the Presidio alone. 

David Luther of George Mason University and Elizabeth Derryberry of Tulane have revisited Baptista’s work. Luther and Baptista collaborated in 1999, finding only two Presidio dialects, with one on its way to becoming dominant. Luther says it has subsequently taken over the city. The dominant dialect has a higher frequency and is presumably more audible over urban traffic. Something similar has been reported for songbirds in Europe. 

With Derryberry, Luther set up iPod speakers near 20 white-crowned sparrow territories in the Presidio and played back songs recorded in 1969 and 2005. The more contemporary songs elicited strong aggressive responses from territory-holding males, reacting as they would to a pushy neighbor. But they hardly reacted to the 1969 songs. 

Next, the researchers plan to test the responses of female white-crowns to songs of different vintages. Do they care if males perform oldies or the avian equivalent of whatever pop-music mutation is currently cutting-edge? I don’t even know enough to provide an example. And, being an old fart, I don’t have to know, which is kind of a relief. 

With the sparrows on my mind, I was intrigued to read yesterday in the New York Times that rock hyraxes, small African rodent-like creatures that are actually next of kin to elephants and manatees, have regional song dialects. Yes, they sing, for 5 to 10 minutes at a stretch. It’s also claimed that their songs have syntax, which is bound to stir up the linguists. (Is there a Chomskyan in the house?) Very likely someone is out in the bush right now tracking trends in hyrax music.