Audio deterrents turned away raptors at U.S. wind farms

A golden eagle approaches a turbine at the Goodnoe Hills Wind Farm in Washington. Before the bird can enter the rotor-swept zone—the danger area swept by the blades—the DTBird system plays a warning sound. In the first North American study of audio deterrents installed at wind farms, researchers found that the birds turned away more than 50% of the time.

The test took place at two commercial sites: the Manzana Wind Power Project in Southern California and Goodnoe Hills in south-central Washington. Teams from H.T. Harvey & Associates, recently merged with Integral Consulting Inc., worked with the Renewable Energy Wildlife Institute. They examined video of golden eagles, bald eagles, turkey vultures and hawks approaching turbines.

The mechanism is deliberately simple. A “whistle-whoop” first draws the bird’s attention; if the approach warrants it, a louder, more raucous dissuasion signal follows. The response varied with species and wind: larger birds were more responsive in stronger winds, while birds already heading along a safer route were less likely to react.

The result has a clear limit. Birds at the highest risk of collision did not necessarily respond best, probably because they could not make an effective avoidance maneuver in time. The study measured behavioral responses rather than a direct reduction in collisions or deaths, so the system’s protective effect still needs testing across more facilities and spatial scales.

So what changes in practice? Wind-farm operators gain a field-tested way to warn approaching raptors before they reach the rotor-swept zone. That could help protect golden and bald eagles, although the study does not establish how many fatalities the system prevents. Its evidence may also inform the U.S. Fish and Wildlife Service in federal policy decisions.