TV, radio towers killing millions of birds, scientists say.

By Margaret Munro

Postmedia News

Ever-taller communications towers in the U.S. and Canada are killing close to seven million birds a year, say wildlife authorities, who are calling for changes that could greatly reduce the carnage.

“This tragedy, it doesn’t have to be,” says Travis Longcore of the University of Southern California, lead author of a study published Wednesday by researchers at Environment Canada and at U.S. agencies and universities.

They recommend that the telecommunications industry change the lighting on tall towers, saying it could almost cut the death toll in half.

The study is the most comprehensive look yet at bird kills at communications towers — a problem that has grown worse with the proliferation of towers that relay television and radio signals across the continent. Some towers are now more than half a kilometre high, held up by many kilometres of cable and wire that entangle birds drawn to the towers’ lights.

The 84,000 communications towers now dotting the continent kill an estimated 6.8 million a year in Canada and the U.S., the study says, up from about 1 million bird deaths a year in 1979. Put another way, the towers kill 27 times more birds each year than the Exxon Valdez oil spill, says the study published in the journal PLoS One.

Most of the casualties are songbirds, such as warblers, orioles, and thrushes, migrating to and from their nesting grounds in North America and wintering grounds in Central and South America. “Many of the birds are of conservation concern,” Longcore said in an interview Wednesday.

Most of the deaths occur in the U.S., which has far more towers than Canada, but Longcore notes many of the birds are en route to Canada.

“These birds, a lot of them are coming up to nest in your forests,” he said.

Millions of the birds don’t make it because they “fall under the spell” of the lights on the towers, that are meant to keep planes at a safe distance.

During bad weather, migrating birds are pushed down by cloud cover and fly at lower altitudes. The clouds also obscure their navigation cues such as stars, and the birds are attracted to the red lights on towers. Then they begin circling round and round the structures.

“They are simply unable to leave the spell of the lights,” says Longcore.

Most of the birds do not die because they run into the towers but because they get caught in the cables and guy wires propping up the structures. Some also run into each other or die from exhaustion.

Studies have shown that solid red lights are the biggest problem. Towers with blinking lights see fewer casualties.

“The minute you turn the light out the birds will disperse,” says Longcore. “It breaks the spell.”

In their study, the scientists challenge the regulators of aviation and communication industries to act for the sake of the birds. They say replacing the steady-burning red lights with blinking lights on 4,500 towers more than 150 meters tall should be a “top priority.” They estimate it could cut mortality by about 45 per cent, or about 2.5 million birds. Longcore says pilots would be able to see the blinking lights and avoid the towers.

The study also recommends that telecommunications companies share towers to reduce their number and build more free-standing towers that minimize the need for guy wires.

“It is simply bad form to go ahead and do something that kills millions of birds a year, when there is a way to dramatically minimize that number,” Longcore said. (He says cellphone towers are not very tall and are not a big killer of migrating birds.)

Pierre Mineau, of Environment Canada’s National Wildlife Research centre, co-authored the report. He was on leave and not available for comment on Wednesday.

mmunro@postmedia.com

Twitter.com/margaretmunro

PN 4/25/12 18:16:53