Light pollution has steadily intensified and expanded in urban areas and, with the advent of LED lightingis growing in North America in up to 10% per year, measured by the visibility of stars in the night sky. In our recent studyWe found that the glow of cities and urban fringes can powerfully attract migratory birds, luring them to developed areas where food is scarcer and where they face threats like collisions with glass buildings.
Every spring and fall, migratory birds travel to or from their breeding grounds, sometimes traveling thousands of kilometers. On the way, most birds need make scales to rest and eat. Some species burn half their body mass during migration.
Migratory stopover locations are not random and birds typically use the same locations year after year. Given that migration occurs on a continental scale, with billions of birds crossing North America With each migratory season, it is important for scientists to understand what attracts birds to these locations.
We found that light pollution was a leading predictor of migratory bird density at stopover sites for spring and fall migration across the continental US.
Why does this matter
Almost all of North America’s birds – about 80% – migrate every spring and fall. And of those species that migrate, 70% travel at night.
Nocturnal migration has many adaptive benefits: for example, weather conditions are better and fewer predators are active. But it makes most migratory birds highly susceptible to light pollution. In North America alone, it is estimated that up to a billion migratory birds die every year in collisions with buildings.
Scientists still don’t know why nocturnal migratory birds are attracted to artificial light, but research shows that light pollution acts as an amplifying agent which attracts more songbirds to urbanized areas. Often co-occurs with other environmental threats, such as water and air pollution and noise. All these stress factors disrupt the behavioral and physiological processes of birds during journeys that are already extremely tiring.
Lighting is part of the fabric of human structures, but many people do not consider it a pollutant or realize its harmful effects on nature – until events like the mass loss of birds in Chicago on October 4-5, 2023, when nearly 1,000 birds were killed after crashing into the McCormick Place Convention Center, make the problem impossible to ignore.
How we did our work
With colleagues from Colorado State University, Michigan State University, University of Delaware, Cornell Lab of Ornithology, Princeton University, University of Massachusetts Amherst, and the National Park Service, we seek to understand the complex factors and large-scale patterns scale. density by combining remote sensing data with geospatial tools. Mapping stopover sites has been a bird conservation priority for many years; Now, for the first time, we have a complete picture of where these stopovers are in the United States.
We were able to make new maps on a continental scale using US NEXRAD Weather Surveillance Data – information from the same radars that meteorologists use to predict weather patterns on television and in weather apps. We created 2,500 models using approximately 1 million U.S. locations and 49 predictor variables, including forest cover, precipitation, temperature, elevation and sky shine – diffuse glow in the night sky due to artificial light.
These maps capture fine-scale details that allow us to observe the increasing density of migratory birds following the winding banks of the Mississippi River, which provide an important refuge for exhausted migrants to rest and refuel. We also created fall and spring hotspot maps highlighting regions where especially high numbers of birds made stopovers.
We found that the presence of light pollution was a better predictor of bird density than temperature, precipitation or tree canopy cover. These were all variables that we expected to correlate with periods when birds would be on the ground or with high-quality habitats where birds were likely to stop.
Other variables were associated with areas that birds were unlikely to use as stopovers. One example was the presence of agricultural crops such as corn or soybeans. Fields planted with a single crop do not provide adequate food or shelter for many bird speciesso migrants are unlikely to rest there.
Light pollution is a human-induced change in the environment that can act as a ecological trap, attracting birds to precarious habitats and increasing the risk of collisions with buildings. Fortunately, its immediate effects can be quickly reversed with the flip of a switch.
Working to reduce artificial light through Deleted campaigns It is migration alerts, understand when birds will be in the airspaces It is Using Bird-Friendly Glass that has patterns on its surface to make it more visible to birds will reduce bird deaths due to light pollution. Understanding the macroscale drivers and patterns of scale densities across the continental US will better inform conservation actions like these.
O Research Summary is a brief overview of an interesting academic work.
This article was republished from The conversation, an independent, nonprofit news organization that brings you trusted facts and analysis to help you understand our complex world. It was written by: Carolyn S. Burt, Colorado State University It is Kyle Horton, Colorado State University
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Kyle Horton receives funding from the National Science Foundation and the National Aeronautics and Space Administration.
Carolyn S. Burt does not work for, consult with, own shares in, or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond her academic appointment.
