Sparrows Tweet Louder To Be Heard In Noisy Cities
Sparrows in San Francisco’s Presidio district changed their tune in order to be heard above the increasing cacophony of car horns and engine rumbles, reports new research from George Mason University. The study focused on the male white-crowned sparrow, a small bird that sports a jaunty white cap with black stripes.
The study, “Birdsongs Keep Pace with City Life: Changes in Song Over Time in an Urban Songbird Affects Communication,” compares birdsongs from as far back as 1969 to today. The researchers also detail how San Francisco’s streets have grown noisier based on studies from 1974 and 2008.
Luther wrote the study with Elizabeth Derryberry, an assistant professor of ecology and evolutionary biology at Tulane University and a research assistant professor at Louisiana State University’s Museum of Natural Science. “We’ve created this artificial world, although one could say it’s the real world now, with all this noise — traffic, leaf blowers, air conditioners,” Luther says.
The study shows a strong link between the change in song and the change in noise, says David Luther, term assistant professor of biology at Mason. It is also the first study to track the songs over time and the responses of birds to historical and current songs.
Just as we raise our voices to be heard when a car speeds past, birds making their homes near busy intersections have to tweet a little louder, Luther says. But it’s more than just whistling the same tune and turning up the volume. Most birds stopped singing some old songs because those ditties couldn’t cut through the racket.
From Click Green:
So the birds changed their tune. Sparrows in the Presidio used to sing in three distinct dialects when famed ornithologist Luis Baptista made his recordings in 1969. When Luther worked with Baptista some 30 years later, those song stylings had dropped to two, with one higher-range dialect clearly on the way to be the only song in town.
“One dialect had basically taken over the city,” says Luther, adding that it is officially called the “San Francisco dialect.”
To do the study, the researchers found territories of 20 sparrows in the Presidio where there’s lots of traffic, especially in the morning rush hour when the birds do most of their singing. They set up an iPod speaker, shuffled the sparrow songs from 1969 and 2005 and waited for a reaction.
“The birds responded much more strongly to the current song than to the historic song,” says Luther, adding that male sparrows flew toward the speaker while chirping a “get out of here” song. “The (current) songs are more of a threat.”
The researchers will next look at how the songs affect female sparrows.
Songs of course need to be heard, not just because they sound pretty — birds use them to talk to each other, warn away rivals and attract mates.
How fascinating that these white-crowned sparrows have been able to stay around by adapting to their environment. Nature is all around us, even in the city!
Photo Credit: ingridtaylar