Light Pollution Increasing Year-Round for Some Migrating Birds

by Pat Leonard, Cornell Lab of Ornithology
March 29, 2022

Ithaca, NY—Nighttime light pollution levels are increasing the most in the southeastern United States, Mexico, and Central America—findings based on year-round data collected over the last two decades in the Western Hemisphere. This trend is a real concern for birds that fly at night during spring and fall migration and even during non-migratory seasons. Results of the study by the Cornell Lab of Ornithology and Colorado State University are published in Ecosphere
“The southeastern United States, Mexico, and especially Central America are important migration corridors,” said lead author Frank La Sorte at the Cornell Lab. “Evidence that nocturnally migrating birds are encountering increasing light pollution levels within these regions is concerning. Birds largely avoid light during the breeding and non-breeding season. During migration, however, these associations break down as birds travel across a wide range of habitats, including populated areas that contain higher light pollution levels.”

Light attracts and disorients birds during migration, often leading to injury and death after collisions with buildings. The authors found that light pollution levels during the past two decades have gone up over roughly 16% of the land area in the Western Hemisphere, with another 7% of land area experiencing a reduction in light pollution. Declines in light pollution are concentrated in the northeastern United States in conjunction with human population declines and urban decay in large cities (map).

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