美国国家公共电台 NPR How To Make Broadcast Towers More Bird-Friendly: Turn Off Some Lights（在线收听）

STEVE INSKEEP, HOST: 

There are more than 100,000 broadcast and cell towers across this country. You use them every time you make a cellphone call or turn on the radio in your car. They're a problem, though, for migrating birds. Every year, millions of birds slam into those towers at night. Ben Thorp of our member station WCMU reports on a simple way to prevent that.

BEN THORP, BYLINE: Likely the only time you really notice one of your neighborhood towers is at night when they're lit up with conspicuous bright red lights. Those lights help airplane pilots see the huge metal structures that can reach a thousand feet into the air, but can spell disaster for birds.

CALEB PUTNAM: For example, in 1976 in Gun Lake, Mich., one tower in one night killed over 2,300 birds.

THORP: That's Caleb Putnam. He works for the Michigan Department of Natural Resources, and says for reasons scientists still can't quite figure out, birds kept flying headlong into towers.

PUTNAM: If that many are dying at one night at one tower, and yet there are thousands of towers across the country and as you go across the world, the numbers are staggering.

THORP: Putnam says in North America alone, it's estimated that 7 million birds smash into towers every year, but until recently scientists didn't know why it was happening. Figuring that out became biologist Joelle Gehring’s mission. She helped conduct a study in 2003 to find out what could be done.

(SOUNDBITE OF MUDDY FOOTSTEPS)

JOELLE GEHRING: I can't not look at the ground when I'm underneath these towers (laughter).

THORP: It's an unusually warm January morning, and the farm fields surrounding this tower are oozing mud. Gehring is standing at a broadcast tower in rural northeast Michigan that belongs to the local radio station. Gehring says every morning in the spring or fall, the peak migration season, she and others had the unpleasant job of counting dead birds at the base of these towers. What she discovered was surprising.

GEHRING: So we were able to reduce the numbers of bird fatalities on communications towers by simply extinguishing those non-flashing lights, and those fatalities were reduced by as much as 70 percent.

THORP: You heard that right - simply turning off the steady beam lights on towers reduce bird fatalities by 70 percent. Exactly why isn't yet clear, but she has a theory.

GEHRING: Some research has documented that when birds are exposed to long wavelengths of light such as red or white, that it actually interferes with their ability to use magnetic fields for navigation.

THORP: Joelle Gehring says that's especially true on cloudy nights when birds can't navigate by the stars. The tower's steady red lights seem to confuse them, flashing red lights don't. In 2015, the Federal Aviation Administration changed regulations on new towers, requiring they all be built with only flashing lights. Gehring, who now works for the Federal Communications Commission, spends much of her time contacting people who run towers built before 2015, encouraging them to switch to blinking lights.

GEHRING: And when we drive back and forth around those beautiful Great Lakes at night, we see more and more communications towers that are lit with only flashing lights at night. And my son always points out - another bird-friendly tower, mom (laughter).

THORP: There are still tens of thousands of towers, though, that aren't bird-friendly, as birds are drawn to the solid red lights. Gehring and others will continue to try to save those birds by doing one simple thing - changing those tower lights. For NPR News, I'm Ben Thorp.