Here's How White Noise Could Save Millions of Birds
Across the United States, bird populations have shrunk by about 3 billion since 1970. As a matter of fact, in New York City alone, approximately 200,000 birds a year die from flying into buildings. As our high-rise cities grow upward and outward, the problem is only likely to grow exponentially, with more and more birds dying by crashing into tall glass buildings, communication towers, and power lines. However, with excellent design, this doesn't have to be the case.
A study from May states we could prevent migratory birds from colliding with high metal structures, tall buildings, and possibly even wind turbines by installing "acoustic lighthouses" that blast white noise in short bursts, a press release states.
The system, called Acoustic Lighthouse, is invented by a group of researchers led by Timothy Boycott from the College of William & Mary. While there are other strategies involving patterned glass and laser lights, the researchers thought the sound would be a better warning as most birds sometimes have a blind spot right in front of them due to the placement of their eyes.
Two types of sound signals were shown to diminish bird activity around communication towers by up to 16 percent in field studies done during the North American fall migration.
During these field trials, researchers used speakers to blast white noise around two communications towers on the Delmarva Peninsula, on the east coast of the United States, in 30-minute bursts. Over the course of six days, two distinct types of white noise were tested to see birds' reactions. One of them was tuned to fit the hearing range of many birds, while the other was tuned to stand out against background noise at higher frequencies.
Flight behaviors of more than 1,500 birds passing within 328 feet (100 m) were recorded, so the researchers were able to determine the numbers of potential birds saved. Both sounds tested prevented birds from flying too close to the towers; however, the lower frequency sound (4-6 kHz) was more successful at making sure more birds steered clear of the towers sooner than under normal conditions.
"[Birds] stayed farther away from the towers and they angled their flight trajectories away from the towers more," Boycott explained. While this would vary by bird species, it could indicate that birds can hear lower frequencies more clearly.
"Future studies would be really important to see how those differences in flight behavior actually translate to mortality on the ground," Boycott added.
However, it should be noted that sound alone may not be enough to deter birds, which is why visual cues could also come in handy. In fact, another study showed painting wind turbines black can reduce bird deaths and the risk of a collision by 70 percent.