If you’ve visited Saint Louis, Missouri, this month, you may have noticed that the Gateway Arch is harder to spot after sunset. You’re not imagining things: Lit up 10 months a year, the national monument’s LED glow is dimmed during September, as well as in May. The reason is to be a good steward of wildlife — specifically, to migrating birds.
About 40 percent of all birds headed south for the winter and north for the summer fly over the Mississippi River corridor, says John Orrell, Gateway Arch National Park’s public affairs officer and partnership coordinator. Even though new lights installed in December 2023 help reduce flare, “light pollution,” as Orrell calls it, can disorient birds, causing them to swerve off their path or into objects.
With the massive Arch — it’s 630 feet tall — in the dark, birds can pass over Saint Louis more safely. The river’s flyway sees about 325 species of songbirds and waterfowl, Orrell says, citing data from the Saint Louis Audubon Society. That includes countless geese making the trip south along the 2,340-mile Mississippi River extending from Minnesota to Louisiana, where it flows into the Gulf of Mexico. “Billions of migrating birds do so at night,” Orrell says, and excessive light “interferes with their ability to endure long-distance migration.”
Technology has made easy the logistics of turning the Arch’s LED lights off and on, Orrell says. The monument started going dark in 2002 only for two weeks in the spring and fall before the timeframes were extended to a full month in May 2023.
Occasional visitors to Saint Louis expecting to see the illuminated Gateway Arch might wonder what’s going on — not after Oct. 1, when the lights come back on — but Orrell says residents of the area have gotten used to the Arch going dark in May and September.
He notes the National Park Service’s core goals are to preserve nature, educate, and inspire, and assisting birds with their migration is in line with those aims. “People get it,” Orrell says. “They are passionate about birds, and they appreciate that we are doing what we can to alleviate light pollution.”
