Migratory birds attracted to light pollution are more exposed to toxic chemicals

The journeys of nocturnal migratory birds are already strewn with pitfalls. Light pollution adds yet another hazard beyond the increased risk of collisions with buildings or communication towers. According to a new study, birds attracted to the glow of artificial light at night are drawn to areas where they are also exposed to higher concentrations of toxic airborne chemicals. The study has just been published in the journal Biology of global change.

“We examined the correlation between the concentration of airborne toxic chemicals, artificial light at night, and the weekly abundance of 165 species of nocturnal migratory songbirds,” said lead author Frank La Sorte. from the Cornell Lab of Ornithology. “What we found was that light pollution actually increases exposure to toxic chemicals when birds stop to rest during spring and fall migration. Surprisingly, we also found that exposure to Toxic chemicals are high outside the breeding season, a time to avoid light pollution.”

Researchers first compared artificial light levels at night with the presence of 479 toxic chemicals from 15,743 release facilities across the continental United States. They found that higher light pollution was correlated with higher levels of toxic airborne chemicals. The scientists then cross-referenced this data with the weekly abundance of 165 species of nocturnal migratory songbirds throughout their annual life cycles, using data from Cornell Lab’s eBird program.

The only time that did not show increased exposure to toxic chemicals was during breeding season, when songbirds typically nest in habitats away from areas of heavy human activity.

“A region of particular concern is along the Gulf of Mexico, particularly in Texas and Louisiana,” La Sorte said. “Migratory birds that overwinter in this region are exposed to higher concentrations of airborne toxic chemicals for a longer period of time – the non-breeding season accounts for the largest portion of life cycles. annuals of these species.

Studies have shown that air pollution has caused some species to stop migrating, change their migration altitude, or alter their trajectory. Long-term exposure to toxic chemicals can interfere with the functioning of cells and organs, and contamination can spread to young through the transfer of chemicals from a nesting female to her eggs.

Altogether, the study shows that the observations provided by volunteer participants in eBird allow scientists to better understand the full range of implications of light pollution for nocturnal migratory birds.

“Efforts to reduce light pollution in the spring and fall would reduce the risk of toxic chemical contamination during migratory stopovers, which would improve survival and reproductive success,” La Sorte said. “However, this would have no effect on long-term exposure occurring along the US Gulf Coast, an area that could be a significant source of toxic chemical contamination for North American birds.”

This work was supported by the Wolf Creek Charitable Foundation and the National Science Foundation.

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