Updated April 29, with spring 2022 dates
The lights on the Gateway Arch will be off at night for two weeks, starting Sunday, May 1. The national park service does this twice a year in the spring and fall to help reduce migratory bird deaths.
Nighttime lights can disorient birds, lead them to collide with buildings or structures, and can even result in their deaths. According to the park service, 40% of the nation鈥檚 migratory waterfowl use the Mississippi river as a flyway on their travels. Migratory songbirds also benefit from the additional darkness.
The Arch started temporary light reductions in 2001. New lights installed in 2018 are more directional, and are intended to be less harmful to birds even when they are on.
Original story from Sept. 16, 2018:
The lights illuminating the Gateway Arch will go dark for two weeks beginning Monday.
The decision is part of a biannual effort to avoid disrupting bird migrations along the Mississippi Flyway 鈥� a critical route used by more than 300 North American bird species. Light pollution from upward-facing spotlights can disorient birds that migrate at night and cause them to collide with buildings.
鈥淲e鈥檝e often been asked, 鈥榃hy do you bother when you鈥檙e in a big city that鈥檚 throwing off all this light?鈥欌�� said Gateway Arch National Park Deputy Superintendent Frank Mares. 鈥淚t鈥檚 because the Arch is possibly the tallest thing any bird will come upon, right on the river.鈥�
Thousands of birds travel along the Mississippi Flyway each year from breeding grounds in Canada to overwintering areas in the southern U.S.
As its name suggests, the flyway hugs the banks of the Mississippi River, stretching from Canada to the Gulf of Mexico.
Many songbirds and waterfowl species migrate at night, potentially to avoid predators. But technological advances have brought stronger, brighter lights that can disorient these nighttime migrants.
In recent years, cities and residents have also installed upward-facing spotlights to illuminate buildings and other structures.
Mitch Leachman, program director for the St. Louis Audubon Society, said these spotlights can be particularly confusing to nighttime-migrating birds. In some cases, birds appear to be attracted to and .
鈥淵ou can see birds flying in the light beam,鈥� said Leachman. 鈥淭hey鈥檙e disoriented, and they can鈥檛 figure out how to get out.鈥�
Although disorientation from artificial light may not directly cause bird deaths, Leachman said it can stress migrants during a taxing period of their lives.
鈥淭hese birds are traveling hundreds 鈥� and in some cases thousands 鈥� of miles. They may be losing 20 to 30 percent of their body weight in doing so,鈥� Leachman said. 鈥淸It鈥檚] an entirely vulnerable part of their life.鈥�
At the request of the St. Louis Audubon Society, park officials decided to turn off the Arch lights temporarily in 2001, the same year the lights were installed.
They now shut off the lights for two weeks during peak migration periods in May and September.
In August 2018, the Gateway Arch exterior-lighting system underwent a , funded by the Gateway Foundation of St. Louis. As part of the project, the 44 original light fixtures were replaced with 26 xenon skylights outfitted with custom lenses.
Mares said the new lights provide a 鈥渓aser-like focus鈥� on the Arch, which he hopes will benefit migrating birds.
鈥淭he lights are brighter, but there鈥檚 much less light overspray than there used to be,鈥� Mares said. 鈥淭here鈥檚 less light pollution above and around the Arch that could disorient a night-migrating bird.鈥�
But to be safe, officials will continue turning off the lights for brief periods to protect birds in the spring and fall.
The Arch lights will be turned back on beginning Oct. 1.
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Reporter Jonathan Ahl contributed to this article.
