REGIONAL— Researchers at the University of Minnesota are hoping that understanding how raptors hear sounds may one day lead to solutions to reduce the frequency of their impacts with wind …
REGIONAL— Researchers at the University of Minnesota are hoping that understanding how raptors hear sounds may one day lead to solutions to reduce the frequency of their impacts with wind turbines. While wind turbines offer a sustainable energy source, they can pose a threat to raptors, including federally-protected species like bald and golden eagles.
Scientists at the U of M’s Raptor Center and the College of Veterinary Medicine recently combined their efforts to get a better understanding of the frequency and sensitivity of hearing in bald eagles and red-tailed hawks. The research was funded by the U.S. Department of Energy, which is looking for ways to reduce bird deaths from wind turbines, particularly of eagles.
Dr. Julia Ponder, executive director of the Raptor Center, said the $300,000 research project is just the first step towards developing methods to effectively deter raptors from flying into the vicinity of wind turbines. Birds can fly into both the enormous towers as well as blades that operate the turbines. Bird strikes into windows, buildings, and towers of all kinds are a leading cause of bird deaths around the world.
Ponder said the dangers posed by wind turbines vary substantially, depending on the kind of turbine and their location.
Until just recently, researchers have known very little about how birds hear sounds. Raptors are known for exceptional eyesight, but their hearing appears to be underdeveloped compared to many mammals. Ponder said the testing conducted at the Raptor Center as part of the study has expanded the understanding of raptor physiology and confirmed that the hearing ability of red-tailed hawks and bald eagles is similar, although the hawks tend to be slightly more sensitive to sound than eagles.
That’s just the first step in determining whether sounds can be used to deter raptors from approaching wind turbines, notes Ponder. Further research will be required to understand what sounds might be effective in either discouraging raptors from approaching turbines or that might help attract them somewhere else. The researchers are hoping to garner additional funding to explore which sounds influence direction of movement and flight paths for red-tailed hawks, bald eagles and golden eagles.
But even if sound can be used to discourage raptor deaths around wind turbines, deploying sounds loud enough for raptors to hear could pose new problems for the developers of wind farms. According to Ponder, birds hear in the same frequencies as humans, which means any sound used to influence the behavior of birds is likely to be audible to humans.
Noise from wind turbines has already been a major issue in some cases, which has made them controversial in more populated areas. That’s likely to be less of a problem, however, when turbines are utilized in more remote locations.
It’s unclear, as well, whether noise could be used to discourage other types of birds from flying near wind turbines. Ponder said while birds tend to hear similarly, they have widely varying sensitivities, which makes it difficult to extrapolate from one species of bird to another, at least without further research.
How big a problem?
There are about 54,000 wind turbines currently operating in the U.S. and the estimates of the number of birds killed through impact with the towers or blades vary considerably. According to the U.S. Fish and Wildlife Service, collisions with wind turbines currently kill between 140,000 and 500,000 birds annually in the U.S. although recent modeling suggests that number could rise to as many as 1.4 million as a result of continued growth in the wind energy sector.
That’s one reason that the Department of Energy is seeking to learn more about how to protect birds from the dangers posed by turbines. A number of possible solutions are being explored, from altering habitat around turbines to reduce bird activity, to modifications to turbines themselves that reduce their reach into the flight paths of migrating birds.
While turbines pose a risk to birds, the risk is actually far less than many other risks that birds face, particularly in migration. The Fish and Wildlife Service estimates that cell towers, for example, kill between five and fifteen million birds annually. Annual bird deaths from window strikes are estimated at between 365 to 988 million birds annually, or many hundreds of times more than are killed by turbines. Domestic cats pose perhaps the biggest risk to birds, killing an estimated 1.4 -3.7 billion birds a year in the U.S.