ST. LOUIS – If you’re driving down the highway towards the city and notice you don’t say to yourself, “Look, there’s the Arch!” because you can’t see it in the skyline, don’t worry—it’s still there. But throughout the month of May, the Arch will be dark.

May marks the peak of bird migration when they travel north for the summer time. The Gateway Arch is located directly in the pathway these birds use, so lights are turned off to help protect them as they travel through.

According to the Arch, more than 320 different bird species utilize the Mississippi Flyway—where the Arch is located—during the migration seasons in May and September.

The park began turning lights off in 2002, but only for two weeks during peak migration season. It wasn’t until May 2023 when the Arch started going dark for the entire month, the National Park Service said.

Last fall, crews installed an acoustic logger with the help of the organization Lights Out Heartland. This technology catches the nocturnal flight calls while on Arch grounds.

Throughout a two-week period set up, the logger caught nearly 600 potential bird calls. At least ten bird species were able to be identified through the sounds, with the most common being the Least Sandpiper and American Redstart.

Lights at the Arch will be back on June 1.