Civilian and military aircraft collide with birds about 40,000 times a year in the United States, causing $700 million in damage annually. Even worse, according to a federal report, from 1990 through 2012, the accidents killed 23 people and injured 240.
A study published this week in The Condor: Ornithological Applications suggests that if the lights on aircraft and along runways are customized to birds’ visual systems, fewer collisions may occur.
Megan Doppler and Esteban Fernández-Juricic of Purdue University and Bradley Blackwell and Travis DeVault of the National Wildlife Research Center’s Ohio Field Station conducted experiments involving captive Brown-headed Cowbirds and remote-controlled aircraft to test how the birds reacted to a variety of lights.
Birds’ eyes are different from human eyes in several key ways, and Doppler and her colleagues determined that blue light (light with a wavelength of 470 nanometers) would be most conspicuous to cowbirds. They outfitted a remote-controlled model airplane with blue lights and tested how the flock reacted to continuous versus pulsing lights and to a stationary versus approaching aircraft.
When the aircraft was stationary and the lights were on, cowbirds became alert more quickly than when the lights were off. When the aircraft approached the birds with lights off, their response times slowed as the aircraft’s speed increased. The birds became more alert when they saw a moving plane with pulsing lights, and they were most likely to get out of the way when approached by a plane with continuous lights.
Finding the right light
“In previous studies, we have demonstrated that avian response to vehicle approach can be enhanced by increasing the conspicuousness of the approaching vehicle with white lights,” explains Fernández-Juricic.
“However, in this study, we followed a sensory ecology approach to establish a priori a light that would be particularly conspicuous to our study species and tested the responses of individuals to this light tuned to their eyes. In addition, we showed that by pulsing the light, we reduced the effects of high speeds on the ability of the animals to become alert to the approaching aircraft. These findings hold implications for how we might enhance bird response to larger, faster aircraft.”
The authors suggest that stationary lights along runways could by synced with taxiing aircraft to help capture birds’ attention before planes take off. Lights onboard aircraft could be off or pulsing during taxiing and on continuously during takeoff to improve birds’ ability to detect and react to the large, fast-moving objects.
Similar approaches may be applicable to reducing bird strikes with towers and wind turbines. In any case, Doppler and her co-authors say that selecting lights based on their conspicuousness to birds’ visual systems may be an important step forward in reducing one of the most common and hazardous human-wildlife interactions.
Read the paper
Megan S. Doppler, Bradley F. Blackwell, Travis L. DeVault, and Esteban Fernández-Juricic (2015). Cowbird responses to aircraft with lights tuned to their eyes: Implications for bird–aircraft collisions. The Condor: May 2015, Vol. 117, No. 2, pp. 165-177. Full text.