Study Finds White Light Lowers Migrating Bird Flight

A Colorado field trial found that white nighttime lighting drew migrating birds closer to the ground than other colors tested.

Updated on Nov. 1, 2026 in Bird Watching

Study Finds White Light Lowers Migrating Bird Flight

Live Poll

Should your community prioritize wildlife-friendly outdoor lighting over brighter white lights?

Researchers tested white, red, amber and blue floodlights over 31 nights on the Colorado plains, using radar to track birds overhead. White light lowered mean bird flight height by an estimated 22.6 metres compared with dark periods, while colour did not change how many birds flew over.

Why it matters

Migrating birds are often drawn to artificial light and can collide with buildings, so understanding which light colours affect flight height could inform lighting choices. A 2023 study ranked light pollution as the second most important of 49 predictors of bird stopover sites.

The trial used two 800-watt LED floodlights cycling through four colours, with a radar sensor aimed straight up tallying birds across autumn migrations in 2023 and 2024. The estimated 22.6-metre drop under white light carries a standard error of roughly 10.5 metres, and the source does not explain how well it would hold at other sites.

The players

Kyle Horton

Kyle Horton led a 2023 study that examined 49 predictors of bird stopover sites and found light pollution was the second most important factor.

The details

Each colour was compared against a dark control using paired periods, with lights off in one period and a coloured light on in the other. Colour did not affect the rate of bird movement, and the study was published in the Journal of Wildlife Management. Scientists sought to determine whether the colour of light affects migrating birds, and the findings could feed into future research and lighting designs that limit harm to migrants.

Autumn 2023: First migration season of the field trial in northern Colorado.
October 2023: Nearly 1,000 birds were killed after colliding with a Chicago building in one night.
Autumn 2024: Second migration season of the field trial.
2026: The field trial paper was published.

Field Evidence

Horton's 2023 analysis placed light pollution second among 49 predictors of bird stopover sites, and the Colorado trial tests which light colours drive that effect by measuring flight height directly. The result narrows the question from whether artificial light affects migrants to which wavelengths do so.

Residents and building managers in Colorado can consider reducing bright white outdoor lighting during migration seasons if future research confirms the effect. The findings may shape lighting choices that limit harm to birds passing through the state.

The takeaway

Choosing warmer or redder outdoor lights during migration may reduce the pull that white light has on birds passing overhead. Bird watchers and homeowners in Colorado can keep this in mind when planning nighttime lighting.