PARIS: From disorientation and risks of fatal collisions to the destruction of ecosystems, the journeys of migrating birds are fraught with many dangers.
The harmful impact of light pollution on night birds has long been known. And to the list of dangers that threaten them can now be added exposure to toxic chemicals.
Indeed, according to a study published in the journal Global Change Biology, birds attracted by artificial light at night are drawn into areas where they are exposed to higher concentrations of airborne toxic chemicals, especially if they migrate along the Gulf of Mexico (the part of the Atlantic Ocean southeast of North America).
To reach these conclusions, researchers from the Cornell Lab of Ornithology (a non-profit organisation located in New York State) observed 165 species of nocturnally migrating songbirds (nightingales, sparrows, warblers, etc.) throughout their annual life cycle.
They then compared nighttime artificial light levels with the presence of 479 toxic chemicals from 15,743 discharge facilities across the continental United States.
The study shows that high light pollution coincides with higher levels of toxic chemicals in the air.
Since birds are attracted to light, this means that they are exposed to these substances, except for during the breeding season, when songbirds generally nest in habitats away from areas of intense human activity.
Previous studies have shown that air pollution has caused some bird species to stop migrating, change migration altitudes or alter their routes.
Long-term exposure to toxic chemicals can interfere with cell and organ function, and contamination can be passed on to young through the transfer of chemicals from a nesting female to her eggs.
This is one more argument for reducing nighttime urban lighting, which has increasingly been called into question in recent months in light of energy saving drives.
“Efforts to reduce light pollution during the spring and autumn would reduce the chances of toxic chemical contamination during migration stopovers, which would improve survival and reproductive success.
However, this would have no effect on the long-term exposure occurring along the US Gulf Coast, a region that could be a significant source of toxic chemical contamination for North American birds,” warns lead author Frank La Sorte of the Cornell Lab of Ornithology.
