Above Iowa is an “invisible highway” along which billions of bats and birds travel southward every fall. It is an expansive nocturnal migratory corridor in the lower atmosphere where wildlife movement is guided by wind currents and geomagnetic cues.
Researchers wanting to understand the changes brought about by wind farms deployed thermal imaging systems above the state’s agricultural landscape.
More than 12,000 thermal flight tracks were analyzed, and it turns out that the animals’ flight patterns were changing.
How thermal imaging delivers trajectory data even in darkness
A great deal of migration happens at night. Field teams had to measure nocturnal migration without artificial lighting, so they turned to high-resolution thermal cameras.
The skies above wind farms in Iowa were monitored by capturing infrared heat signatures from birds and bats passing through the cooler night skies.
Using custom tracking algorithms, 12,047 distinct flight paths were recorded. Ground speed, direction of flight, and elevation were logged over several weeks of fall.
The monitoring array also recorded the weather conditions, including wind speed, temperature, and barometric pressure.
Another metric applied was pairing timestamps with operational turbine logs. This enabled researchers to compare stationary baseline controls against operational periods.
Data was also drawn from a 3D tracking system whereby animals inside the rotor sweep zone were mapped between 130 and 500 feet above ground level.
By comparing the data from when the turbines were active against periods when they were idle, researchers could isolate how flight density and spatial distribution were altered across Midwestern agricultural landscapes.
Operational turbines drive avoidance maneuvers and lane displacement
When the 12,000-plus thermal tracks were analyzed, it became clear that path changes occurred when wind farms were active.
When the blades were not moving, migrating animals moved straight through or over the facility.
When wind speeds exceeded startup thresholds after the blades started turning, animals on the approach changed direction hundreds of feet before reaching the rotors.
The behavior is mainly presented as a side-to-side displacement—similar to how drivers change lanes on a highway. Migrants exhibited directional deflection away from the rotor-swept zone, with significantly stronger avoidance observed when the turbines were in operation.
The odds of the bird or bat changing course increased with proximity and the speed of the blade motion.
The pass-through rates remained high during the times that the turbines were idle. When power operations started again, systematic path detours were noted.
These quantitative tracking records show that flying animals detect kinetic structures from a distance.
They adjust their routes early to bypass moving aerodynamic obstacles on their migratory path.
Aerospheric conservation strategies and smart curtailment trade-offs
Animals change lanes by sensing physical cues created by spinning blades long before collision risks occur.
While migrating birds and bats show significantly stronger avoidance behavior near operating turbines, the specific sensory mechanisms driving this response—such as visual blade motion, low-frequency acoustic cues, or wake turbulence—remain unresolved.
This quick transition explains how flying creatures dodge moving blades in low-light conditions.
This spatial diversion shows that wind turbines alter aerosphere use without always causing direct collisions.
Taking forced detours means consuming extra energy
However, forced detours impose cumulative energetic costs, making animals burn extra energy steering around dense wind developments along major flyways.
These tracking insights offer valuable operational guidance for wildlife conservation and green energy planning. Rather than establishing smart curtailment as a corridor-preservation tool, the findings emphasize the importance of radar-informed facility siting, identifying turbine-associated sensory cues, and further evaluating targeted mitigation strategies.
Balancing clean power generation with dynamic airspace management ensures expanding wind developments do not fragment essential migratory pathways.
The full study can be found here: Shultz, A., Solick, D., Whitby, M., Newman, C., & Corcoran, A. (2026). Integrating 3-D thermal videography, ultrasonic acoustics, and weather radar to characterize bird and bat activity at wind turbines. PLoS One, 21(7), e0352329.
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