Light pollution is a growing issue for migratory birds

Light pollution can be a real problem for migratory birds that fly by night. Light can attract but also confuse birds, causing them to fly into buildings and become injured or die. 

Some migratory birds are facing more light pollution on both ends of their migrations, according to new research from scientists at the Cornell Ornithology Lab and Colorado State University.

“The southeastern United States, Mexico, and especially Central America are important migration corridors,” said study lead author Frank La Sorte of 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.”

Although light pollution is decreasing in some parts of the Americas, the researchers found an increase in about 16 percent of the land area of the western hemisphere. By contrast, only seven percent of the area had a decline in light pollution.   

Using eBird, a popular citizen science web service, the scientists looked into the occurrence of 42 species of migratory birds. The bird occurrences were then correlated with light pollution data collected by satellite over 22 years. 

The scientists found that all of the birds experienced increases in light pollution, with birds migrating through Central America facing the greatest increases. Conversely, birds living year round in the northeastern US had the smallest amounts of light pollution increases, in fact much of this region has decreased in light pollution. 

“Reversing light pollution trends in Central America, especially during the spring, and launching Lights Out programs during intense migration periods could save a substantial number of migrating birds,” said study co-author Kyle Horton of Colorado State University. “Reversing light pollution trends in the southeastern United States during the summer breeding season and in Central America during the winter non-breeding season would generate the greatest benefits outside of migration periods.”

The researchers hope that by identifying the biggest problem areas of light pollution, a plan might be developed to help migratory birds facing too much light. 

The study was published in the journal Ecosphere. 

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By Zach Fitzner, Earth.com Staff Writer