BOISE, Idaho -

Scientists who built a "phantom road" high on an Idaho ridgeline say they've demonstrated how traffic noise can interrupt songbird migration.

Boise State University professor Jesse Barber and his team erected a half-mile string of tree-top loud speakers above Idaho's Snake River Plain in 2012.

When a tape played sounds of cars and trucks barreling along, the number of songbirds declined by more than a quarter, with some species disappearing almost completely, they found.

Funded by the National Park Service and published recently in a respected British scientific journal, the team's work could eventually guide wildlife managers trying to balance the interests of visitors driving through America's preserves and with the concerns of the wildlife they have come to see.