WASHINGTON — Is the pursuit of fewer dropped calls leading to more dropping birds?
The lights atop communications towers that warn pilots to stay away can have a come-hither effect on birds -- killing millions of migrating warblers, thrushes and other species every year.
During bad weather, birds can mistake tower lights for the stars they use to navigate. They will circle a tower as if in a trance, often until they crash into the structure, its guy wires or other birds. Sometimes disoriented birds simply plummet to the ground from exhaustion.
The fatally hypnotic effect of warning beacons on birds is not a new phenomenon; early lighthouses attracted swarms of birds. But as towers proliferate to accommodate an ever-growing number of mobile phones and other devices, conservationists say bird deaths are climbing.
"We're talking about estimates of millions of birds dying because of these towers," said Paul Schmidt, assistant director for the migratory bird program at the U.S. Fish and Wildlife Service, which has pegged the annual deaths at 4 million to 50 million.
Precise numbers are elusive because many of the approximately 105,000 lighted communications towers nationwide are in isolated areas, and scavengers waste little time feasting on the dead birds.
It's another example of the conflict between technology and nature -- a battle that has not gone well for migratory birds. Not only are their habitats being lost to development, their flyways are increasingly mined with deadly windmills, power lines and confusing reflective-glass skyscrapers.
Lacking definitive studies on birds and towers, the communications industry questions the wisdom of adding costly new regulations at a time when more towers are needed for expanding cellular phone service and high-definition TV and radio broadcasts.
"We don't want to be anti-conservation ... but you have to sort of balance that with this transition we're making to this next generation of technology," said Dennis Wharton, a spokesman for the National Assn. of Broadcasters. "So far, according to our engineers and scientists, it's still open to a lot of debate."
That debate has begun in Washington.
Can blinking lights help?
Spurred by environmental groups, the Federal Communications Commission announced this month that it was considering new tower regulations. The agency is asking for more data about the effect of a tower's height and the use of steadying guy wires. And the commission is proposing that new and modified towers use more expensive white strobe lights instead of the steadily burning red ones now on most towers.
Researchers say red light waves may interfere with the magnetic compass of migratory birds, and some studies have indicated that blinking lights are less alluring.
"If you have a strobe light that even allows for a momentary period of darkness, it breaks that sort of spell and the birds are allowed to escape," said Darin Schroeder, deputy director of conservation advocacy at the American Bird Conservancy.
Researchers first noticed birds' strange attraction to lights in the night sky more than 100 years ago when they flocked to the beacons of lighthouses.
After explosions at offshore oil platforms, the glow of the flames has lured scores of birds to fiery deaths.
"We don't completely understand it," said Travis Longcore, science director of the Urban Wildlands Group, a Los Angeles-based conservation organization.
"They will not leave the zone of the light. They will be attracted to it and circle it."
It's not just big, bright lights. The Federal Aviation Administration requires communications towers taller than 200 feet or close to airports to have warning lights for pilots. To a migratory bird's brain, those lights can be mistaken for stars when clouds block the real ones.
Birds migrate using celestial navigation. Stars stay fixed in the sky even as birds travel hundreds of miles -- the same way the moon appears to follow you as you drive. But when birds try to keep a tower light in a fixed location, it causes them to circle in confusion.
For 40 years, Charles Kemper, a bird enthusiast from Chippewa Falls, Wis., studied the phenomenon at a nearby TV tower. He counted more than 120,000 dead birds there until he stopped in the mid-1990s. One late summer morning in the 1960s, he said, he and a friend picked up 11,000 carcasses.
"For a long time it was one of the only towers in the area," Kemper said. "Now we have cell towers all over the place."
A matter of costly rewiring
The communications industry has exploded over the last decade. The number of cellular transmitting sites has increased to 197,576 this year from 24,802 in 1996, according to CTIA -- the Wireless Assn., a trade group for the mobile phone industry. Those aren't all towers; several cell antennas can cluster at one spot and they can be placed on water towers and other tall structures.