Traffic noise is just another inconvenience for many of us. But for wildlife, noise from honking, and zooming vehicles can often be an insidious threat: it can degrade habitats without leaving any physical evidence of change, warns a recent study published in the Proceedings of the National Academy of Sciences.
Road noise — even in moderate levels — pushes migrating birds away from their stopover habitats, researchers from Boise State University in Idaho found. Those that stay back become weak.
“I was initially surprised that even moderate road noise — comparable to a suburban setting — would have such a wide-ranging impact on migrating birds,” William Laurance, a professor at James Cook University in Cairns, Australia, who was not involved in the study, told Mongabay. “On reflection, however, I guess such migrators have to be hyper-vigilent about noise, as they’re constantly moving to new areas where unseen predators could be lurking.”
Threats from roads can be aplenty. To tease out the independent impact of traffic noise on birds from those of other threats, such as collisions, visual disturbance, and chemical pollution, the team set up an elaborate experiment. They created a “phantom road” — a road that was made out of noise alone.
Along half-kilometer forested section in Lucky Peak State Park in southwest Idaho, the researchers arranged an array of speakers that played road noises at moderate volumes, simulating traffic on an actual road.
The team also kept this phantom road away from any actual road noise by keeping the speakers’ locations very remote, Heidi Ware, lead author of the study, told Mongabay. This meant hiking and backpacking with 40 pounds of batteries a day to keep the phantom road running, she added.
In addition, the team had a comparable control site nearby that lacked any traffic noise. Then for two years, between 2012 and 2013, the researchers counted the number of migratory birds coming to the area, and assessed their body condition.
“Migration is an energetically stressful time,” Laurance writes in a commentary about the study. So any unpredictable noise in their stopover locations could potentially affect the time they spend being vigilant or feeding, ultimately affecting their health.
The team found that around 31 percent of the birds kept away from the phantom road. Of the remaining birds that stayed, most suffered loss of body mass.
Continue reading at ENN affiliate, MONGABAY.COM.
Noise pollution image via Shutterstock.