In a recent post, we lamented that high levels of noise in urban areas were pushing the numbers of certain bird species down due to overlapping frequencies between human noise and crucial elements of the birdsongs. Amazingly, this is not as much of a problem for the Black Capped Chickadee, a chameleon of sorts in the songbird world. Armed with the Wildlife Acoustics SM1, the same Dr. Proppe from the study in Canada investigated the birds’ strategy to adapt and thrive in city environments.
Nowadays, because of the low frequencies that traffic noises produce, we are finding that birds by busy roads tend to have high frequency calls as they avoid overlap in the sound spectrum. However birds that sing the higher pitched songs are making a trade off. Higher frequencies don’t travel as far as low ones do, and therefore the range of their audience is smaller. In addition, lower-pitches are a signal for dominance in their world, and that’s an important trait to convey to neighboring females as well as rival males within hearing range. Still, a bird that sings a high-pitched song and is heard wins out over the male who isn’t heard at all. So what is a bird to do?
Well if you’re a Black Capped Chickadee, you can have your cake and eat it. The Chickadees possess what’s called short-term behavioral plasticity. They adapt, adjusting the frequencies of their songs in a way that is most advantageous given the level of noise surrounding them.
In Dr Proppe’s study, the chickadees sang higher pitched songs when traffic noise was high, and lower-pitched songs when the noise subsided. In addition, they sang shorter songs in areas of high noise. This served two purposes: it meant less energy expenditure and also that they could better fit the songs between short bursts of traffic. With such a knack for adapting in a modern environment, it’s no wonder these birds are so abundant in forests in urban areas.
Photo by jackanapes in Flickr