They called it Phantom Road.
Researchers at Boise State University and the Idaho Bird Observatory created it to study the effects of road noise on migratory birds.
Other studies have shown that there are effects of roads but did not filter out factors other than noise, such as visual or chemical stimuli, road mortality or habitat fragmentation.
“Our aim was to tease apart noise as an independent stimulus. We know that roads probably affect wildlife. Noise has been implicated repeatedly, but never as an independent factor,” said BSU researcher Jesse Barber, assistant professor of biology.
“Birds are great because they are the canaries in the coal mine (of roads). It’s an animal dependent on sound.”
A third-of-a-mile array of 15 pairs of speakers were placed along a ridge in a roadless area, creating a phantom road. Noise was introduced on a four-day-on, four-day-off cycle to test the effects on migrating songbirds.
Daily surveys were taken within 55 yards of the test area.
“Twenty-five percent of the songbird community leaves when road noise was introduced,” Barber said. A control area showed no such results.
More than half of the species responded negatively to the noise.
Species with significant differences in abundance during background noise levels were American robin, ruby-crowned kinglet, spotted towhee, red-breasted nuthatch, Cassin’s vireo, Western tanager, chipping sparrow, mountain chickadee, cedar waxwing, yellow warbler, dusky flycatcher and Townsend’s warbler.
Only the Cassin’s finch was positively associated with the site noise. But in some sections, the yellow warbler completely avoided the “road,” Barber said.
It’s likely that other factors would add to the effects of road noise, according to researchers.
If bird sounds are masked by roads, changes in behavior are likely to happen, since birds use sound for mate attraction, territorial establishment and defense.
It’s possible that the stress of road noise can ultimately impact survival. Is there a solution?
“I’m not a noise engineer,” Barber said.
“A lot of work is being done to make urban environments quieter. (Noise has been shown) to have negative impacts on human health and learning in school children. There have been some limited quieting efforts in this country; Europe has done a lot,” he said.
“We can make roads with quieter surfaces, reduce speed limits, put roads underground, and install noise barriers along the roads that potentially can make a difference.
“But noise walls might create a different movement among animals, and the barriers could do more harm than good,” he said.
It’s a societal issue. The role of the ecology research community is to see how much of a problem a louder world would be for all wildlife. Birds play a pivotal role, dispersing seed, controlling insect populations, possible top-down effects on ecosystems. It could be dramatic.
“There are many outstanding research questions but certainly, with the evidence, policymakers can start considering the acoustic environment as an important priority in the conversation.”
Columnist Sharon Wootton can be reached at 360-468-3964 or www.songandword.com.