Mass bird mortality events have occurred in recent years in major cities and have captured national headlines. In October 2023, over 2,500 birds were killed at McCormick Place on the Lake Michigan waterfront in Chicago. It was a “perfect storm” with an unprecedented number of fall migrants drawn to the glass building after lights inside were left on overnight. Three years earlier, on October 2, 2020, an estimated 1,500 fall migrants died in Center City Philadelphia, drawn in by the city lights and unable to differentiate between the glass buildings and open sky. Similar incidents have been reported in Galveston, Texas; at New York City’s “Tribute Lights”; and in other urban areas. These tragic events highlight the deadly combination of artificial light and glass for birds.
Dr. Jeffrey Buler at the University of Delaware has been at the forefront of scientific research on this issue, documenting how artificial light at night dramatically impacts migrating birds. Using weather radar data, his research shows how light attracts migrants to urban stopover areas, increasing their risk of building collisions.
These mass mortality events have occurred during spring and fall migrations, when millions of birds travel between northern breeding grounds and their wintering grounds in the south. Most songbirds migrate at night, navigating by the stars and other environmental cues. At dawn, they “fall out” to rest and forage before continuing their journey the following night. For thousands of years, this extraordinary migration strategy has been successful. However, in the last century, human-made environments—particularly light and glass—have introduced new and serious threats.
In response to these threats, a growing movement has emerged. “Lights Out Philly” and “Bird Safe Philly” were created following the October 2020 Philadelphia mortality event. The tragedy received significant media coverage and spurred action. A coalition—including the Academy of Natural Sciences, the Delaware Valley Ornithological Club, the National Audubon Society, and two local Audubon chapters, Liberty Bird Alliance and Valley Forge Audubon Society—formed to launch the “Lights Out Philly” campaign in spring 2021. More than 100 buildings voluntarily turned off their lights every evening from midnight to 6:00 AM during critical spring and fall migration periods. The program has continued to grow, with increasing participation across Philadelphia and the surrounding counties in southeastern Pennsylvania and New Jersey.
Inspired by Philadelphia’s efforts, a similar initiative began in Harrisburg. The Appalachian Audubon Society and the Pennsylvania Department of Conservation and Natural Resources (DCNR) led the effort to establish “Lights Out Harrisburg.” A coalition of business and government leaders supported the launch, and major buildings—including the Pennsylvania Capitol Dome—dimmed their lights during migration to emphasize the importance of this effort. Appalachian Audubon built and continues to maintain the “Lights Out Harrisburg” website. Now in its third year, the organization has expanded the program by launching “Bird Safe Harrisburg.” This past spring, volunteers monitored walking routes around major buildings to document bird collisions. Recruitment and training for volunteers to cover the 2025 fall migration is already underway.
Several proactive efforts have grown out of these “Lights Out” and “Bird Safe” campaigns. Appalachian Audubon has initiated glass retrofit projects at select facilities, including the Olewine Center at Wildwood Park. DCNR has enrolled state parks in the initiative, reducing or eliminating unnecessary lighting at their sites. Bird Safe Philly has implemented retrofit projects at environmental education centers in the region and launched a “Bird Safe Schools” pilot at Springside Chestnut Hill Academy. In Chicago, the Audubon Society partnered with Feather Friendly, a manufacturer of bird-safe window film, to retrofit all glass at McCormick Place—leading to a dramatic reduction in bird deaths at the site. Meanwhile, New York City has enacted an ordinance requiring bird-safe glass in all new construction.
Legislation is now pending in the Pennsylvania General Assembly: the “Responsible Outdoor Lighting Control Act,” which would apply to government buildings and serve as a model for private development. The hope is that the message is getting through—and that ultimately, birds will be the beneficiaries.
To learn more about Lights Out and Bird Safe initiatives, visit the Pennsylvania Audubon Council’s website here.