AUDIE CORNISH, HOST:
Wildlife researchers estimate that each year nearly seven million migrating birds die because of communications towers. The big problem, according to researchers at the University of Southern California, are the solid red lights on these towers - lights required by the FAA - in order to that are meant to warn aircraft pilots.
Scientists say the light causes a kind of vertigo and a recent effort in Michigan to temporarily turn the lights off during migrating season cut the number of bird deaths there by more than half.
I'm joined now by Travis Longcore. He's an associate professor of spatial sciences at USC and coauthor of a recent study about this red light effect. Travis, welcome.
TRAVIS LONGCORE: Hi. How you doing?
CORNISH: So, to start, bird vertigo - I don't know if that's really a scientific term. What exactly does it mean? What was happening to the birds here?
LONGCORE: Well, people have observed for a very long time that nocturnally migrating birds are attracted to lights at night and it's exacerbated during periods of bad weather and there's research that suggests that they can't use their magnetic compass where they detect the magnetic field of the Earth under a red light, especially, and other light of longer wavelengths. And so it leaves them circling these towers that they encounter and running into either the guide wires on the towers, each other, ending up on the ground and taken by predators, etc.
CORNISH: Ending up on the ground, meaning they fly until they're exhausted?
LONGCORE: Yes. They get exhausted. They collide with things. They may be injured and then they're picked off by an owl or something. So we're looking at probably, on the tallest towers, there's a few birds a night, but in extreme events, you can get hundreds or even thousands have been recorded.
CORNISH: Now, these towers have a steady red light and a blinking one. Can you describe what, specifically, the problem is with the light and is the color a factor?
LONGCORE: Right. So the solid lights appear to the be the key issue. Red seems to be worse than other parts of the spectrum, but we also know that solid white lights attract birds, as well. So it's like it breaks the spell, as it were, to have that break in a dark period so the birds aren't kept there in that zone of influence.
CORNISH: So what's the solution to this problem? How did the FAA react to it?
LONGCORE: Well, there's two agencies involved. One is the FCC, which regulates the construction and registration of the towers and the other is the FAA, which deals with air safety. And, because of the research that's been done showing the number of birds being killed at these towers, along with the proposed solution, which is to go to flashing lights only, the FAA has just completed what they call a conspicuity study, where they have shown that towers that just have the red flashing lights without the solid red lights are equally conspicuous to pilots and therefore equally safe.
The FCC has said that could be OK, but it doesn't appear to me yet that they're going to mandate this on existing towers, which is something from a conservation - sort of a humane perspective I'd like to see so that we can avoid this sort of needless death of so many of these birds, which are all - 97 percent of them are songbirds. About half of them are warblers and the rest are thrushes and sparrows and things and these are birds that actually have an important role in our ecosystems. They're insectivores. They keep insect populations in check, keep our forests healthy and many species that die at towers are also of conservation concern and declining for various other reasons in addition to tower mortality.
CORNISH: Travis, thank you for talking with us.
LONGCORE: It's been my pleasure. Thank you.
CORNISH: That's Travis Longcore, associate professor of spatial sciences at the University of Southern California talking about how turning off steady red warning lights could reduce the number of bird-tower collisions. Transcript provided by NPR, Copyright NPR.