April 15, 2009 -- Millions of birds die every year from nighttime collisions with communication towers. But there may be a simple way to save tons of avian lives -- without tearing down towers or sacrificing airplane safety.
All we have to do, suggests a new study, is change some light bulbs so that steady lights become blinking lights.
"The potential is that all the communication towers in the world could potentially be changed to be better," said Terry Rich, director of Partners in Flight, a bird conservation group, in Boise, Idaho. He was not involved with the new study.
"That would save millions and millions of birds," Rich said. "It's hugely important. It's hard to overemphasize what the potential is."
An estimated 4 or 5 million birds die each year in the United States from flying into communications towers, said Joelle Gehring, lead author of the new study, though some estimates range as high as 50 million birds a year. Migratory songbirds are the most common victims of tower collisions. And most run-ins happen at night, which is when these birds tend to travel.
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Scientists suspect that migratory birds use stellar constellations and other light cues to navigate. If the animals encounter other lights along their journey, they can become easily confused, especially if fog, clouds or rain push them down to lower altitudes and obstruct their view of the stars.
Befuddled birds often circle illuminated towers before ramming into them or the wires that connect them to the ground. These structures are lit at night so that pilots can avoid them.
"We knew these towers were involved in collisions for decades," said Gehring, a conservation scientist at the Michigan Natural Features Inventory in Lansing. "But we never dove into why and how we could prevent it."
Gehring and colleagues happened upon the perfect natural experiment. The Michigan state police maintain a network of communication towers that were built around the same time and are all equipped with the same lighting systems. Best of all, the police department agreed to give the researchers full access to the towers, including the ability to fiddle around with the way the lights glowed at night.
The scientists randomly selected 21 towers around the state. All of the towers were about 470 feet tall. And each was assigned to one of four lighting scenarios: Blinking white lights; blinking red lights; red lights that alternate between bright and dim without ever shutting off completely; and steady-burning red lights that don't blink at all.
For 20 days, a huge network of researchers and volunteers walked around each tower at the same time every morning, picking up bird carcasses and sending them to Gehring for counting and analysis.
The final tally revealed that lighting alone has a huge impact on bird deaths.
"Those towers that had steady-burning red lights had significantly more collisions than all of the other three combined," Gehring said. "We could reduce avian collisions by as much as 70 percent, just by turning off those steady-burning lights."
For now, the Federal Aviation Administration approves only steady-burning reds and blinking whites. But those policies are outdated, Gehring said, and the FAA is planning to re-assess the safety of other scenarios.
It would be not only easy and cheap to switch steady reds over to blinking reds, she added. The change would also save energy and reduce maintenance costs.
"If the FAA deems it safe," she said, "That's a win-win."
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