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As America celebrates its 250-year anniversary, the Liberty Bell pavilion in Philadelphia is hosting millions of people from across the country. Recent upgrades, however, were designed to accommodate an entirely different kind of visitor. 

̽����ѡ Mid-Atlantic worked with other members of Bird Safe Philly  (including the Liberty and Valley Forge chapters, the Delaware Valley Ornithological Club and the Academy of Natural Sciences of Drexel University) to enable the National Park Service to install a bird-friendly window treatment that uses patterns of UV light to prevent migratory birds from colliding with the Liberty Bell pavilion's expansive glass windows.  This approach also preserves a key feature of the structure’s design – the ability to easily see the Liberty Bell through the building’s windows.  

“The Liberty Bell is a symbol of American history, and now it’s also helping to write a new chapter for bird conservation,” said Keith Russell, Urban Conservation Program Manager at ̽����ѡ Mid-Atlantic. “This project shows that protecting our historic landmarks and the wildlife that shares these spaces can go hand in hand.” 

Each spring and fall, over forty million birds migrate through the city of Philadelphia as they travel between their breeding grounds and wintering areas. During migration, most of these birds fly at night, using the earth’s magnetic field, the position of the stars, and other signals to navigate. Artificial light can lure birds off course, while glass can appear invisible or reflect open sky and habitat. As a result, more than 1 billion birds are estimated to die from building collisions each year in the United States. 

Independence National Historical Park, home to the Liberty Bell and other landmarks associated with the American Revolution, became a priority for collision monitoring after community members reported frequent bird strikes at the park’s modern buildings and because the park was a site that was easy to access for monitoring and research. 

Bird Safe Philly found that bird collisions were occurring at all of the park’s modern buildings, and the Liberty Bell pavilion was the first park building to be retrofitted in part because the work aligned with preparations for the nation’s 250th birthday. While Independence National Historical Park and the National Park Service planned, managed, and funded the entire project, Russell initiated the park monitoring project in 2021 and managed the subsequent reporting efforts that helped to inspire and guide the retrofit work.    

This spring, contractors completed the addition of Bird Divert, a bird-friendly window treatment manufactured by Feather Friendly, to the pavilion’s 9,000 square feet of glass. The nearly transparent product is only slightly visible to people but highly visible to birds, significantly reducing collisions without compromising the transparent nature at the historic site.  

This technology isn’t limited to historic landmarks. Homeowners and businesses can also install bird-friendly window treatments to reduce bird collisions while maintaining clear views through their windows. 

Monitoring of the structure will continue over the coming months and years. Similar treatments have been shown to reduce bird-window collisions by an average of nearly 80%.  

Bird-friendly building practices gained momentum in Philadelphia following a devastating 2020 mortality event  Bird Safe Philly was formed shortly after. Led in part by ̽����ѡ Mid-Atlantic,  advances migratory bird research, public education, bird-friendly building improvements, and participation in the nationwide Lights Out initiative, which encourages reducing unnecessary nighttime lighting during peak migration. 

As we celebrate America’s 250th anniversary, the Liberty Bell stands not only as a symbol of our nation’s past, but also as an example of how preservation and innovation can join together to support a more sustainable future.