By Mona Sabalones Gonzalez
Urban birds are changing their song. We mean that literally. Mating calls in the past, in a quiet jungle were usually low frequency and rather nice. With the noise pollution of the city’s technology, mating calls need a high pitch to be heard. A study in the
showed that female birds find the high pitch mating call less sexy. Netherlands
The study was done by Wouter Halfwerk, behavioral ecologist at
. The paper was published in the Proceedings of the Leiden University, Netherlands of the Sciences. National Academy
The study showed that because of all the noise in the city—airplanes, car engines, construction noise, etc., male birds were forced to raise their mating calls to a higher pitch.
High pitched sounds can be heard better at short distances, and are good in a noisy environment. For example, the laughter of children can cut through lots of background noise because it is high pitched.
But female birds prefer low pitched sounds. The trouble is, in the city, these mating calls are drowned out by the surrounding noise. Halfwerk was able to discover this by studying the Great Tit, a bird that can imitate the sounds of up to 30 random birds in the
Halfwerk recorded the mating calls of 30 different male Great Tits, half of which gave high pitch sounds, and half who gave low pitch sounds. He then conducted paternity tests on the hatched eggs of the female birds who responded to the calls.
Most birdies were the offspring of male birds that used low frequency sounds. The study stated the low-pitched male birds probably swooped down in the last minute to lure the female out of her nest and fertilize her.
Halfwerk then played the mating calls of the birds that were prerecorded. They noted that female birds responded to the low pitched sounds. However, when they added urban noise to the background of the low pitched mating calls, the females were drawn to the high pitched mating calls, most likely because these were the sounds they could hear.
It’s understandable why female birds would be more drawn to low frequency sounds. In a forest, these are the sounds that have long wavelengths. They can bend around the trees and other forest barriers, and go long distances. Birds traditionally sing in low frequency sounds.
The study concludes that noise pollution can affect bird populations in a negative way.
Here’s an amazing BBC video of a bird that copies a wide range of jungle sounds in the forest, including a chainsaw!