Like moths to a flame, light pollution poses a huge risk to migratory birds. Researchers collaborating with the 9/11 Memorial and Museum have shown that birds migrating above Manhattan, New York will have trouble completing their migrations because they flock toward bright light and become highly disoriented.
Since the majority of birds migrate by night, scientists at various institutions, including Cornell University and New York City Audubon, were interested in figuring out just how much migratory birds were affected by light pollution. They set out to conduct a unique seven-year experiment in which they used the 9/11 Memorial and Museum’s public installation titled “Tribute in Light” to observe changes in bird behavior, which they have published in the Proceedings of the National Academy of Sciences.
Every year, the “Tribute in Light” is held to memorialize lives lost during the tragic Sept. 11, 2001 terrorist attacks. Two bright beams of blue light are cast into the sky on the night of Sept. 11 from atop the Battery Parking Garage south of the 9/11 Memorial and can be seen from 60 miles in any direction.
Within the bright beams were thousands of migratory birds that would have looked like tiny stars franticly meandering through the night sky.
Researchers estimated that over a million birds were affected by the light over the course of their seven-year study. In fact, birds become denser the closer the observation were made to the beams of light. Compared to the amount of birds in the surrounding area – in other words, the baseline density of birds – there were 20 times more birds near the light installation than there would have been without the installation.
The numbers get even bigger in certain years. For example, five of the years had 60 times more birds while three of the years had 150 times more birds.
Imagine viewing Manhattan on a map that lights up red where thousands of birds are all congregating in the same place. When the lights are off, there’s nothing much too see. When the lights get turned on, a big red blotch begins to appear.
Researchers also reported widespread disorientation among the massive flock of birds that had effects 2.5 miles into the air. Disoriented birds tend to call more than non-disoriented birds and that’s exactly what researchers found. Near the light installation, there were over 600 calls every minute when the lights were on compared to 300 calls every minute when the lights were off.
The birds also began to slow down. Despite being on a migratory route, they were shown to reduce their flight speeds three-fold, which could prevent them from successfully completing their migratory journey.
It’s clear that we humans have tremendous effects on nature globally. Whether that’s by cutting forests down, polluting soils and water, fragmenting terrestrial and coastal habitats or fueling climate change, our societies must coordinate collectively if we are to protect and preserve the planet on which we depend.
Light pollution is one of the concerns that needs to be addressed. Migrating birds not only include a big chunk of biological diversity, they interact with insects, plants, bacteria and viruses in ways that we are only just beginning to understand.
We can mitigate those effects by turning off at least some of our lights when birds are migrating.
Diler Haji is a campus correspondent for The Daily Campus. He can be reached via email at firstname.lastname@example.org.