While the journeys of night-migrating birds are already fraught with dangers – such as increased risk of collisions with buildings or communication towers – a research team from Cornell University has identified yet another hazard these birds currently face. According to the experts, migratory birds attracted by the glow of artificial lights at night are drawn into regions in which they are also exposed to higher concentrations of airborne toxic chemicals.
“We examined the correlation between the concentration of airborne toxic chemicals, artificial light at night, and the weekly abundance of 165 nocturnally migrating songbird species,” said study lead author Frank La Sorte, an expert in Ornithology at Cornell. “What we found is that light pollution does indeed increase exposure to toxic chemicals when birds stop to rest during spring and fall migration. Surprisingly, we also found that exposure to toxic chemicals is high during the non-breeding season, a time when birds typically avoid light pollution.”
In a first step of the study, the scientists compared levels of artificial light at night with the presence of 479 toxic chemicals from 15,743 releasing facilities across continental U.S., and found that higher light pollution did correlate with higher levels of airborne toxic chemicals. Then, they cross-referenced these data with the weekly abundance of 165 night-migrating songbirds throughout their annual life cycles.
The analysis revealed that the only instance without increased exposure to toxic chemicals was during these birds’ breeding season, when they usually nest in habitats far away from areas with intense human activity.
“One region of special concern is along the Gulf of Mexico, especially in Texas and Louisiana,” La Sorte reported. “Migratory birds that spend the winter in this region are being exposed to higher concentrations of airborne toxic chemicals for a longer period – the non-breeding season makes up the largest portion of these species’ annual life cycles.”
According to La Sorte, efforts to reduce light pollution during the spring and autumn could reduce the chances of toxic chemical contamination during migration stopovers, thus improving the birds’ survival and reproductive success. “However, this would have no effect on the long-term exposure occurring along the U.S. Gulf Coast, a region that could be a significant source of toxic chemical contamination for North American birds,” he concluded.
The study is published in the journal Global Change Biology.
Image Credit: Craig Kerns, Cornell Lab of Ornithology
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