"Protecting birds from glass is a monumental task, spanning across every state and country. In the USA alone, 1.3 billion birds die annually. If we birders don't take action, who will?"
Article and photos by Stephen Maciejewski
Disclaimer: This article discusses bird-window collisions and includes descriptions and photos of bird mortality that may be upsetting to some readers.
What is a bird-window collision, and why do birds hit windows?
A bird-window collision, also called a window strike, happens when a bird flies into a glass surface—like the window of a house, office building, car, or skyscraper. It can be fatal or leave the bird stunned and injured.
But why does this happen so often?
The short answer: birds can’t see glass the way we do. Glass reflects the environment—trees, sky, clouds—so birds think they’re flying into open space. Sometimes, glass is transparent, and if a bird sees light, plants, or sky on the other side, they might try to fly through it. They're also drawn to lights at night, especially during migration. For birds, glass can be a deadly illusion.
How did you get into window strike monitoring?
I first got involved in 2008, working on a bird collision monitoring project in Center City Philadelphia. It was a collaboration between Audubon Pennsylvania, the Philadelphia Zoo, and the Academy of Natural Sciences.
Back then, few people paid attention to this issue. Maintenance crews would throw stunned or dead birds into the trash. Because it was shortly after 9/11, people were suspicious of anyone out at odd hours—I was even accused of being a terrorist for walking around from 5:30 to 8:00 AM documenting collisions. One day, the police blocked me from leaving a site.
Eventually, support faded and the program was suspended.
I shifted my focus to plant conservation in China, cofounding the Gesneriad Conservation Center of China. We now have seven centers protecting rare and endangered plants.
Years later, a friend, Michael LoFurno, asked me, “What are you doing for your first love—birds?” That question stuck with me.
So, in the Fall of 2020—during the height of the COVID-19 pandemic—I started monitoring window collisions again. Since then, I’ve gone out every migration season, about 186 days a year, collecting data, helping injured birds, and raising awareness.
What’s one of your most unforgettable experiences?
On October 2, 2020, just a month after restarting my monitoring, I witnessed a massive bird kill in downtown Philadelphia. Over 1,000 birds—colorful neotropical migrants—died or were injured near buildings like the Comcast Technology Center/Four Seasons Hotel, the Comcast Center and One, Two and Three Logan Square.
At the time, I had no idea this was a “mass kill." I did not know what was happening. I felt like a war correspondent—powerless to stop it, but driven to document everything. It was heartbreaking, picking up bird after bird.
Journalist Frank Kummer of The Philadelphia Inquirer covered the story, and it quickly gained national and international attention.
That day is burned into my memory. The lines from William Butler Yeats's poem that I read half a century ago kept echoing in my mind:
Turning and turning in the widening gyre
The falcon cannot hear the falconer;
Things fall apart; the centre cannot hold;
Mere anarchy is loosed upon the world,
The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.
But something changed that day. Building staff helped me collect birds. The public took notice. Soon after, Bird Safe Philly was formed, and Lights Out Philly became a reality.
Here’s the good news: bird-window collisions are preventable. There are tons of simple fixes, and you can be part of the solution.
Make Your Windows Bird-Safe
Dots or patterns on glass: Apply decals, tape, or paint in a pattern no more than 2 inches apart. (Try products like Feather Friendly.)
Screens or netting: These act like a soft barrier between birds and the glass.
Close your blinds or curtains at night, especially during spring and fall migration.
Move bird feeders closer to windows—within 3 feet—so birds can’t build up enough speed to get hurt if they fly into them.
Change Your Lighting Habits
Use motion sensors or timers for outdoor lights.
Choose blue or green lights instead of white, red, or yellow—they’re less attractive to birds.
Point outdoor lights downward, and use shields to minimize light pollution.
Educate & Take Action
Talk to your school, nature center, or local government about adding bird-safe glass or retrofitting windows.
Use apps like iNaturalist to report collisions. The more data we collect, the more we can push for change.
Start a bird strike monitoring team at school and work with wildlife rehab centers to save stunned birds.
Document High Collisions Areas (HCA)
Donate dead birds to museums like the Academy of Natural Sciences of Drexel University for scientific study.
Looking at a bird up close—even in sad circumstances—lets you appreciate its beauty and fragility. It's a powerful reminder of why this work matters.
Education is everything.
Most people don’t realize how dangerous windows are for birds until they see it firsthand. But once they know, they care—and they act.
Take the Sister Cities Café in Center City, for example. This beautiful “green building” used to be a death trap for birds. Its glass walls reflected surrounding trees and native plants. But after adding simple dot patterns every 2 inches, bird collisions dropped by 98%.
That’s the kind of change we need—and it starts with awareness.
We are engaging with several building owners, like the Comcast Technology Center, the Comcast Center, Ciocca Subaru at 1400 S. 33rd Street and the Constitution Center at Independence National Historical Park at 525 Arch St. in Philadelphia, to encourage them to take the next steps toward making their buildings bird-friendly and reducing bird collisions.
Every generation faces unique challenges. When I was 16, I spent my summer reading Silent Spring by Rachel Carson and the Life Histories of Birds by Arthur Cleveland Bent and birding with an old-timer named Ted Allendorf. He told me stories of seeing over 100 species in a single day along Pennypack Creek in Philadelphia.
Today, you face different—but just as urgent—challenges.
Dive into Daniel Klem’s Solid Air: Invisible Killer-Saving Billions of Birds from Windows to understand the contemporary threats birds face. Here’s what I know: Your passion for birds will guide you.
Whether you're a beginner or seasoned birder, your voice, your data, and your advocacy matter. You can help birds survive—and thrive—for generations to come.
Want to get involved?
Visit American Bird Conservancy for resources
Join or start a Bird Safe Philly or Lights Out program.
Follow your curiosity—it might lead you to your own unforgettable moment in bird conservation.
For additional information:
Kummer, F. (2020). "Up to 1,500 birds flew into some of Philly’s tallest skyscrapers one day last week. The slaughter shook bird-watchers." The Philadelphia Inquirer. Published: October 7, 2020.
Maciejewski, Stephen. (2025). "What is Happening? Documenting a Massive Bird Kill in Center City Philadelphia." Cassinia 79_66-73.
