White light lowered migrating birds’ flight height even in a dark rural corridor
WHAT THE EVIDENCE SAYS
Across 31 fall-migration nights, researchers alternated white, red, amber and blue LED treatments with dark controls while vertical radar measured passage. Broad-spectrum white light produced the clearest reduction in mean flight height, while migration traffic rate showed no treatment effect.
WHY IT MATTERS / OUR READ
Artificial light can alter movement behavior before it produces an obvious change in counts. Infrastructure assessments that monitor only passage rate may miss changes in flight altitude that could affect collision exposure or energetic cost.
CAVEATS / UNCERTAINTY
The study used one remote corridor and a particular point-source lighting configuration. Flight-height change is a behavioral response, not direct evidence of collision mortality or population effect, and spectral and brightness conditions matter.
SOURCE
Journal of Wildlife Management
View original evidence ↗
A Colorado field experiment found broad-spectrum white LEDs reduced average nocturnal migration height by about 23 metres without changing migration traffic rate.
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