Bird Safe Philly

Scope of the Problem

Weather radar has shown that tens of millions of migrating birds can pass through Philadelphia in a single month, and that these birds stop to rest and feed in our natural spaces in huge numbers, especially in our parks. Because Philadelphia is a key location that so many of North America’s migratory birds pass through each spring and fall, any hazards that can kill large numbers of these birds could directly impact the entire population of many bird species.

The largest number of individual birds and variety of species generally occur each year during the spring migration (mid-February through early June) and the fall migration (late July through late November), but the number and variety of migratory birds that occur during fall is always larger than the number and variety that occur during the spring.

Up to one billion birds are estimated to collide with buildings and other human made structures in the U.S. every year, and billions of additional birds probably collide with buildings each year in other parts of the world. These collisions occur because artificial light at night and/or glass cause birds to fly into buildings and other human made structures. Unfortunately, most of these collisions are fatal.


Most species of birds migrate at night using a variety of cues to find their way, including the earth’s magnetic field and the position of the stars. Because birds are particularly sensitive to light when they are migrating at night, artificial lights at night can disorient them, particularly during cloudy or rainy weather when the celestial cues they use to navigate may be not be visible. Under these circumstances birds may congregate around artificial lights causing them to collide with various parts of the buildings associated with lights, much like a deer in headlights.


Reflective and transparent glass exteriors, indoor plants, and greenery close to buildings can all create confusing situations for birds who often mistake the reflections they see on windows and other glass surfaces for real scenes, or mistake transparent glass surfaces for clear passage ways to fly through. Birds do this because most wild birds, unlike most household pets, have never had an opportunity to learn what glass is, so they need strong clues on or around glass to warn them that it’s there.  Read more on how to prevent birds from hitting windows here.


Bird Safe Philly was created was to help reduce significant hazards that harm large numbers of birds that migrate through the Philadelphia area.

Bird Safe Philly is a partnership led by the Academy of Natural Sciences of Drexel University, Audubon Mid-Atlantic, Delaware Valley Ornithological Club, National Audubon Society, Valley Forge Audubon Society, and Wyncote Audubon Society. The Bird Safe Philly partnership aims to create safe spaces for birds by developing awareness of the issue of bird collisions and implementing solutions, working in partnership with the Philadelphia community. Through Lights Out, Collision Monitoring, and Taking Action, Bird Safe Philly strives to engage individuals, organizations, and the community in better understanding bird collisions and the solutions that can be implemented to help prevent these collisions.

Learn more about the Bird Safe Philly program and how to participate at

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