Where birds that migrate at night are most at risk from the combined effects of light and air pollution

Ithaca, NY—Birds that migrate at night face many threats during their journeys, including light and air pollution. Scientists led by Cornell Lab of Ornithology documented where the combined risks of light and air pollution are greatest for the world’s night migrating birds. Their findings are published in Global Ecology and Biogeography.
 
"We compiled global databases of light and air pollution," explained lead author Frank La Sorte at the Cornell Lab. "We then intersected these data with range maps of 225 species of nocturnally migratory birds in three migration flyways located in the Americas, Africa-Europe, and East Asia-Australia."
 
What they found is that light and air pollution were positively correlated across seasons and flyways. The East Asia-Australia flyway had the strongest positive correlations and the highest light and air pollution levels. The combined threats of light and air pollution were lowest and, in some cases, decreasing within the Americas and the Africa-Europe flyways.

Migrating birds are attracted to light at night, increasing the risk of building collisions that could cause serious injury or death. Air pollution can affect breathing and hamper the ability of birds to fly to their breeding or wintering grounds. When light and air pollution occur together, which is common in large cities, the effects of light pollution on migratory behavior could increase exposure to air pollution.
 
"Improving air quality and reducing light pollution levels would generate the greatest benefits within the East Asia-Australia Flyway," said La Sorte. "We need to explore how different forms and sources of environmental pollution act in combination to affect migratory birds, especially during migratory flight and stopover. This information will enhance conservation efforts directed towards preserving the world's nocturnally migrating birds."
 
Reference:
Frank A. La Sorte, Myla F. J. Aronson, Chris A. Lepczyk, and Kyle G. Horton.
Assessing the combined threats of artificial light at night and air pollution for
the world’s nocturnally migrating birds. 2022. Global Ecology and Biogeography.