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On the morning of October 2, 2020, Ô¼ÅÚÊÓƵ volunteer Stephen Maciejewski and I had the sad task of collecting hundreds of birds that had died colliding with buildings that day in Philadelphia. The historic mass collision event, centered in the downtown section of the city, was caused by an unfortunate combination of circumstances: A large number of migratory birds were passing through Philadelphia during the peak of fall migration when they encountered severely overcast skies, rain, and fog. This caused many of them to fly toward bright lights emanating from the city’s tallest and most brightly lit buildings and eventually collide with them.  

That incident led to the creation of , which is one of many local groups working across the U.S. and Canada to make cities safer for migrating birds. The Bird Safe Philly partnership—Academy of Natural Sciences of Drexel University, Delaware Valley Ornithological Club, Ô¼ÅÚÊÓƵ Mid-Atlantic, the Ô¼ÅÚÊÓƵ, and local chapters Valley Forge Ô¼ÅÚÊÓƵ Society and Wyncote Ô¼ÅÚÊÓƵ Society—is focused on protecting birds in the Philadelphia area from a variety of issues that can cause them to collide with buildings and other human-built structures. Bird Safe Philly created and now manages the Lights Out Philly program, oversees bird collision monitoring in Philadelphia, and also works to address the collision problem through advocacy and education. 

This month Bird Safe Philly celebrated the installation of a . Located in the heart of the downtown area, the cafe has been monitored by Bird Safe Philly since the fall of 2020 and found to be highly prone to collisions. This small, one-story cafe is a perfect example of how collisions can occur at buildings of all sizes and heights. The mostly glass building was causing collisions because at times the exterior was covered with the reflections of surrounding trees and vegetation that birds can easily mistake for reality. At other times the exterior would lack any reflections, causing the building to appear completely transparent and almost invisible.

Fortunately, when Stephanie Egger, a member of the Bird Safe Philly management team, approached the cafe and the business advocacy group Center City District with monitoring data and clear recommendations for solving the building’s collision issue, they allowed Bird Safe Philly to pay for rows of collision-preventing vinyl dots—manufactured by and installed by —on all of the building’s glass walls and windows. , , and raised and contributed funds to support the retrofit. No collisions have been observed at the cafe in the three weeks since the dots were installed.

Why Bird-Friendly Buildings and Lights Out Programs Are So Important 

Cities like Philadelphia are critical for birds like the Black-throated Blue Warbler and American Woodcock during their spring and fall migrations. These are just two of many bird species that are especially prone to collide with buildings; building collisions are now believed to be one of the leading direct-human causes of bird mortality, with Thankfully, two strategies have been proven to significantly reduce the number of bird collisions: turning off artificial lights at night and placing collision-preventing patterns or materials on or in front of glass surfaces. The decals and raptor silhouettes that are often used simply don’t work because birds will just fly around them and crash into other sections of a window. Multiple markings spaced two to four inches apart work best.  

Unfortunately, the mass collision event in Philadelphia was not an isolated incident. This month in Chicago, 1,000 songbirds collided with a single building in one night. Lights Out and building retrofit programs are needed to prevent birds from colliding with buildings, outdoor glass walls, transit shelters, sound barriers and other types of human-built structures. But many building owners and managers know very little about the collision issue. That’s why it is so important that the Lights Out network is growing. Education is often needed to convince building owners and managers to participate, and this is best accomplished by not only sharing data about the overall number and variety of birds lost to collisions each year, but also sharing data about collisions occurring at their own buildings if that information can be obtained. Participation in these types of programs would increase if federal legislation like the were to finally be passed. But ultimately, this and similar legislation will be most effective if participants are already aware of the issue and ready to adopt collision preventing measures.

Making Birds Safer in the Mid-Atlantic Region

Despite the horrific nature of the October 2, 2020 event, it has led to a number of positive outcomes including the creation of Bird Safe Philly, Lights Out Philly, and the Sister Cities Cafe retrofit – one of several retrofit projects completed since 2021. It also led to the expansion of collision monitoring work in the downtown section of the city. The creation of Bird Safe Philly inspired the creation of similar organizations designed to protect migrating birds from collisions in and . Bird Safe Philly continues to help raise public awareness about collisions through work with partners in the building industry to use bird friendly buildings techniques and materials voluntarily. And while there is still a great deal of work to do to protect birds from collisions with buildings, we know that Rome wasn’t built in a day. Every small step we take to address the problem is adding up to help create a safer world for birds in the future.