If birds could speak, they'd have many complaints to make about roads. There's the swift violence of a death between rubber and asphalt. There are the streetlamps, which make nighttime activity far less discreet. There’s the pollution. And, perhaps worst of all for a group of crooning animals, there is the ceaseless noise of traffic.
Any new road brings those various harms to birds all at once, so it’s tough to figure out what parts are most harmful. But proximity to roads is shown to affect the breeding rate, number of birds, and diversity of species—and not in a good way. That is why a group of researchers decided to build a different kind of road through Idaho's Lucky Peak State Park. They left out the lights and the cars and the asphalt, and instead paved a half-mile road of noise, which they called a "phantom road." By stringing up speakers playing the sounds of recorded traffic, they aimed to identify how the sound of traffic alone affects birds in the area.
Once everything was in place, the team turned the road on and off for four-day stretches throughout the autumn months, just as migrating songbirds were flocking to the ridge… They found the phantom road drove a third of the local birds away from the ridge. And those that stayed didn’t have it easy. At least five species, including MacGillivray’s Warblers, Western Tanagers, and Cassin’s Finches, were substantially lighter for their size if they arrived when the road was in effect compared with their counterparts who arrived when the road noise was turned off.
Head over to the Atlantic to find out why traffic noise prevents birds from feasting in a forest full of berries. It might just shed some light onto why a bird would avoid crossing or even approaching a road—unless it's a chicken, anyway.