How to Prevent Birds from Flying into Windows
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Time to read 8 min
Window collisions are one of the top causes of bird mortality, and they’re almost entirely preventable. In this article, we explain the problem and offer practical solutions. The focus is on individual actions (spoiler alert: there are lots of things you can do at home!), but we also spotlight broader community efforts.
The first step to solving the problem is to understand why bird-window collisions happen.
Table of Contents
Why do birds fly into windows? How big Is the window collision problem? The 2x4 Rule: What Actually Makes Windows Bird Safe Effective Ways to Stop Birds from Hitting Windows Do window decals and bird-friendly applications actually work? Won’t bird-proofing spoil my views? What should I do if a bird hits my window? What can I do to protect birds in my community?
Why do birds fly into windows?
Birds fly into windows because they don’t understand glass. They can’t see it the way we’ve learned to through experience; nor do they register it as a physical barrier.
It’s not that they’re stupid; birds routinely achieve incredible feats of aerial navigation at which we humans can only marvel. Unfortunately, we’ve changed the environment for these feats. Birds are hard-wired to feed, reproduce, and in many cases migrate, but they’re not hard-wired to navigate a hall of mirrors.
Take a moment to imagine what birds see as they fly through a human-built environment full of material that is transparent, reflective and unforgivingly hard. As they descend after a long migratory journey, or move from one group of trees to another in search of food, or dart to seek shelter, their keen eyes spot their objective and calculate their course.
Birds often collide with windows because reflections of trees and sky make glass appear like real habitat.
And then – wham.
In some cases, a bird flies into a window because the patch of open sky or habitat that attracted it was behind transparent glass. This is more likely in commercial spaces or convention centers, where banks of windows surround lush atria and offer panoramic views. In the more common scenario, affecting residential, commercial and public buildings alike, a bird flies into a window because it mistakes a reflection of habitat for the real thing.
During the breeding season, these same reflective properties can lead male birds to attack windows in the belief that their own reflection is a territorial rival. While these frenzied encounters aren’t likely to be immediately fatal, they can go on for hours and leave the bird exhausted.
How big Is the window collision problem?
The bird-window collision problem is huge. Researchers estimate that window strikes kill a billion birds in the United States every year. As tempting as it is to put the blame on commercial skyscrapers, the overwhelming majority of fatal window strikes occur at or below 11 stories.
A 2014 study published in the journal of the American Ornithological Society remains the most detailed and widely cited source for the incidence of fatal window strikes by type of building. According to the researchers, single family homes account for an estimated 44 percent of deaths. Almost all the remaining carnage involves structures of 4 to 11 stories, including many apartment buildings. While some urban skyscrapers are notorious bird-killers, there simply aren’t enough of them to contribute more than a percentage point to the overall death toll.
The fact that the problem is so widely dispersed is daunting, but it also means there’s much that individuals can do to fix it.
Most bird-window collisions happen at homes and low-rise buildings, making residential areas a major source of bird mortality.
The 2x4 Rule: What Actually Makes Windows Bird Safe
Stopping birds from hitting your windows takes more than slapping up a falcon silhouette and calling it a day. The good news is, it doesn’t take that much more. The key is creating a dense pattern that breaks up the reflections that lure birds to windows. To do this, follow the research-tested 2x4 rule: elements in horizontal rows should be spaced no more than 2 inches apart, and elements in vertical columns no more than 4 inches apart. Protective patterns should always be placed on the outside of the glass. Applying them indoors won’t stop your window from acting like a mirror, confusing birds and causing collisions.
Effective Ways to Stop Birds from Hitting Windows
- Window film and tape. A number of companies sell adhesive films and tape that you can apply to your windows yourself. A quick internet search will bring up various products and styles; for a thorough overview, the American Bird Conservancy has a database of products. We personally like Feather Friendly bird collision tape. White decals are best for applications where glass is primarily reflecting sky or habitat (most residential windows), and black decals are recommended for situations where birds are seeing through the glass, such as with railings.
- Tempera paint, washable markers or soap. Let your imagination run wild! This DIY option, using soap or washable paint, can be fun for kids. It’s best for temporary or seasonal use, and in rainy weather, you may need to reapply it.
- External barriers. Screens, netting, beaded curtains and dangling cords can be effective, as long as they’re properly installed outside. You can purchase them from companies offering bird safety items, or you can rig up your own.
- Bird-safe glass and UV solutions. For new construction or renovations, bird safety can be designed into glass by bonding patterns to the exterior surface. Some patterns, like those made with glass frit, are visible to humans; others, like UV coatings, are visible to birds but outside our visible range. The cost differential versus conventional glass varies, so if you’re looking at new windows, it pays to research and ask questions.
- Assess your bird feeder placement. If you have feeders in your yard, be sure to keep them out of the collision danger zone. The safest distance from windows is either less than 3 feet or more than 30 feet.
If you’re not able to bird-proof all your windows at one go, don’t give up. Identify the ones that, because of their size or location, are the most likely to cause problems, and start there. You’ll still be making a positive impact.
Do window decals and bird-friendly applications actually work?
Yes, bird-friendly building materials work. Organizations like New York City Bird Alliance has been conducting scientific research on collisions, and has documented incredible decreases when buildings treat their glass. The NYC Javits Convention Center was once one of the city’s deadliest buildings for birds, but after a 2014 renovation that replaced its reflective façade with bird-safe glass, collisions went down by 90%. Other rigorous academic studies, some in the field and others using controlled flight in specially-designed tunnels, confirm the effectiveness of simple collision-prevention measures.
Won’t bird-proofing spoil my views?
Effective bird-proofing doesn’t mean blocking natural light or spoiling your views. Many patterns are subtle and unobtrusive, while others feature eye-catching designs.
What should I do if a bird hits my window?
Sadly, no preventive measure is 100 percent effective. Here’s a step-by-step guide to what to do if a bird collides with your window, or if you come across a window strike victim elsewhere.
If the bird is alive:
- Don’t just leave it! Almost all window strike victims are at least concussed, leaving them vulnerable to predators and passing traffic. Approach the bird slowly, lift it with your hands around its wings, and put it in a container that’s dark but ventilated, like a brown paper bag or a cloth tote. Close the container securely.
- Keep the contained bird in a quiet place and contact a local wildlife rehabilitator. Don’t know one? The Humane Society maintains a list of resources by state.
- Do not attempt to give the bird food or water. This is not what an injured bird needs and may further harm it.
- Transport the bird to the rehabilitator as soon as possible.
If the bird is dead:
- Snap a picture, if possible.
- Report the collision (including location, time and date) on dBird. This data will help researchers and advocates prevent window collisions.
- Dispose of the bird’s body. Wrapping it and putting it in household trash is fine.
Sadly, no preventive measure is 100 percent effective. Here’s a step-by-step guide to what to do if a bird collides with your window, or if you come across a window strike victim elsewhere.
If the bird is alive:
- Don’t just leave it! Almost all window strike victims are at least concussed, leaving them vulnerable to predators and passing traffic. Approach the bird slowly, lift it with your hands around its wings, and put it in a container that’s dark but ventilated, like a brown paper bag or a cloth tote. Close the container securely.
- Keep the contained bird in a quiet place and contact a local wildlife rehabilitator. Don’t know one? The Humane Society maintains a list of resources by state.
- Do not attempt to give the bird food or water. This is not what an injured bird needs and may further harm it.
- Transport the bird to the rehabilitator as soon as possible.
If the bird is dead:
- Snap a picture, if possible.
- Report the collision (including location, time and date) on dBird. This data will help researchers and advocates prevent window collisions.
- Dispose of the bird’s body. Wrapping it and putting it in household trash is fine.
What can I do to protect birds in my community?
Taking individual action is important, but so is spreading the word. You can help by talking with your friends, family and neighbors about the window collision problem and how simple it is to fix. If you live in a multi-unit building, speak with your building’s management, either individually or, even better, with a group of neighbors.
In many communities, bird advocacy organizations have launched volunteer monitoring programs to document the problem, and lobbying efforts to fix it. You can read more about these initiatives in our blog post on Making Bird Migration Safer. If you live in a city where such efforts are already underway, consider joining them. If not, what’s stopping you from starting your own?
Summing up.
Here are the key things to know about birds and windows:
- Window collisions are a major cause of bird mortality.
- Private homes and low-rise buildings account for almost all deaths.
- Most collisions are caused by reflections.
- Solutions are simple and cheap.
- Effective prevention requires dense patterns (the 2x4 rule) placed on the outside of the window.
