Even a specific count of dead birds at the foot of a tower may be misleading. Many animals feed on the birds, and at one site other researchers saw an owl snatching birds out of the sky as they plummeted toward the ground.
The new study indicates it may be possible to reduce the number of tower deaths dramatically, but it's not as easy as it might seem.
"We certainly aren't asking that any towers be torn down," Longcore said. But he and his colleagues would like to see the static lights replaced with flashing lights.
However, that's within the jurisdiction of the Federal Aviation Administration, which is focused more on aviation safety, as it should be, than bird mortalities. FAA regulations are broad, leaving specifics up to regional safety officers, because conditions vary greatly across the country. What works on the Great Plains, where so many of the taller towers are located, may not work in the Rocky Mountains.
The agency is looking at the bird problem, along with the U.S. Fish and Wildlife Service and the Federal Communications Commission, but there has been no official announcement.
"The FAA is very deliberate and measured and careful in what it approves," Longcore said. But he would like to see those static red lights replaced, as long as air safety is not compromised.
Meanwhile, nocturnal migrators will continue their dangerous journeys every spring, and every autumn. It's a wonder they make it at all.