Road noise is clearly a stressful experience for wildlife. But the din from traffic is actually causing songbirds physical harm, says a study out of Boise State University.
Many birds just avoid stopping near busy roads, but those that don’t may suffer from decreased “body condition.” That is, they get thinner and more emaciated. And although the study only looked at birds, the same could be true of other animals.
Researchers built a half-mile “phantom road” along Idaho’s Lucky Peak. The virtual street used speakers to simulate the sounds made by a road. By eliminating air pollution and all other physical manifestations of a real road, the team, led by Jesse Barber, could study the effects of noise alone.
Battery-powered horn speakers fired the sound of cars, recorded from a real road, out into the forest, for four days at a stretch. The result? The birds didn’t eat much. The area where the experiment took place is a “critical staging ground for migrating songbirds,” says the Atlantic, and the birds stop off there to feed before flying south. Compared to similar birds a the nearby Intermountain Bird Observatory, fully a third of birds left the Phantom Road right away. The rest ate so little that their overall body condition decreased by a full standard deviation. Body condition is a five-point measure of the size/weight of birds, and runs from “obese” to “severely emaciated.” A full standard deviation is a big deal.
Barber and his team think that the road noise puts the birds on constant alert. Because the din drowns out natural sounds, the birds have no way to check for predators other than to look up and scan their surroundings. This extra heads-up time means less time to eat, which may account for the weight loss.
Next up for Barber is a study of insects. If road noise affects them, then it could also affect plant life in the area, as well as any animals further up the food chain. We already know that traffic noise is killing humans by disturbing our sleep and causing stress, which is why plans that aim to reduce traffic noise in cities are so important. Now it seems like we should be reducing traffic noise even in places where few humans visit.