Understanding how raptors hear may help prevent future wind turbine deaths

While wind turbines provide sustainable energy solutions, they also pose a threat - raptors that hunt by day, such as eagles and hawks, are frequent casualties of turbine collisions. 

Researchers at The Raptor Center (TRC) in the University of Minnesota College of Veterinary Medicine hypothesized that adding devices to turbines that emit sound could deter eagles from approaching them, but they first had to determine what eagles can and can not hear. Their findings were published in the Journal of Comparative Physiology.

TRC researchers collaborated with the University’s Center for Applied and Translational Sensory Sciences and the St. Anthony Falls Laboratory to map what eagles and red-tailed hawks could hear. The researchers deciphered which strength of sound (in decibels) and frequency of sound (in Hertz) produced a nerve response in the brains of nine bald eagles and seven red-tailed hawks. 

The study found:

  • the two species have slightly different sensitivities, with red-tailed hawks being more sensitive to sound than eagles; and 
  • despite these subtle differences in sensitivities, the responses of bald and golden eagles are close enough to those of red-tailed hawks that the researchers believe hawks may be a surrogate for eagles for future hearing studies.

"While we don’t know the underlying ’why’ for these differences, because almost nothing is known about the underlying anatomy or physiology, it is reasonable to speculate that hawks have a larger number of auditory nerve fibers," said study co-author Julia Ponder , executive director at TRC. "If so, this may have implications on how they perceive sound." 

The researchers are now hoping to garner funding to explore which sounds influence direction of movement and flight path for red-tailed hawks, bald eagles and golden eagles.