Telecom towers are killing nearly seven million birds every year as they migrate from the US and Canada to Central and South America, says a new study.
According to the study, around 84,000 telecom towers, some of which can rise nearly 2,000 feet into the sky, much higher than the Empire State Building at 1,250 feet, dot the two countries.
However, the birds are killed not by running into the tower itself but the dozens of cables, known as guy wires, that prop up the thin, freestanding structures, said study co-author Travis Longcore, associate professor at the University of Southern California Spatial Sciences Institute, US. "This is a tragedy that does not have to be," added Longcore.
The taller the tower the greater the threat, the study found. The 1,000 or so towers above 900 feet accounted for only 1.6 percent of the total number of towers. Yet these skyscraper towers killed 70 percent of the birds, about 4.5 million a year, Longcore said, the journal the Public Library of Science ONE reports.
During bad weather, the birds were pushed down by cloud cover and flew at lower altitudes. The clouds also removed navigation cues, such as stars, leaving only the blinking or static red lights of towers. The blinking did not fool the birds, but towers with a static red light resulted in more dead birds, according to a Southern California statement.
"In the presence of the solid red lights, the birds are unable to get out of their spell," Longcore said. "They circle the tower and run into the big cables holding it up."
Longcore estimated that changing the steady-burning lights on the 4,500 towers greater than 490 feet tall (about six percent of the total) could reduce mortality about 45 percent, or around 2.5 million birds. The study also recommended that businesses should share towers to reduce their number and build more freestanding towers to reduce the need for guy wires.
The study did not include shorter towers that typically are used for transmission.