If you look at the St. Louis skyline after sunset this month, you may notice something missing. The Gateway Arch will still be there, but the famous monument will not light up again until October.
The National Park Service is keeping the Arch’s exterior lights off every night throughout September to protect birds migrating south for the winter.
According to the official announcement, the lights went off on Sept. 1 and will return on the evening of Oct. 1. The change only involves the exterior lighting, so people can still visit the Arch during the day.
St. Louis sits along the Mississippi Flyway, one of the busiest bird migration routes in North America. Approximately 40% of the country’s migratory waterfowl use the Mississippi River corridor during their spring and fall travels.
The Arch Has Been Going Dark Since 2002
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The National Park Service began turning off the Arch’s exterior lights during bird migration in 2002. The monument also went dark throughout May this year as birds traveled north for the spring.
New lights installed in December 2023 reduced the amount of glare sent into the night sky. However, the park says shutting them off completely is still the best choice during the busiest migration months.
Bright Lights Can Pull Birds Off Course
Many birds migrate at night, when bright lights can make the trip much more dangerous. According to the U.S. Fish and Wildlife Service, nighttime lighting can attract migrating birds from as far as about three miles away.
Some birds become stuck circling the lights and use energy they need to complete their trip. Others become confused and crash into buildings or other structures.
The problem can get even worse on foggy or cloudy nights. Birds tend to fly lower, while light reflecting against the clouds makes it harder for them to find their way.
People Can Help by Turning Off a Few Lights
If you’d like to help migrating birds, turning off any unnecessary outdoor lights at home or work can help make their migration safer.
It also helps to close blinds at night so indoor light doesn’t shine outdoors. If you have any lights that need to stay on, shine them toward the ground instead of at the sky.