Few things are more heartbreaking than looking out the window and seeing a bird lying still after a collision. A peaceful morning of backyard bird watching can quickly turn into a moment of worry when a bird unexpectedly flies into glass, leaving many people wondering what went wrong—and how they can prevent it from happening again.

If this happens at your home, you may find yourself asking the same questions many bird lovers do: Why do birds keep flying into my windows? How can I stop them from hitting the glass? And what can I put on my windows to prevent future collisions?

While these collisions may seem like rare accidents, they are sadly anything but uncommon. Known as bird-window strikes, they are a major threat to birds across North America.

“Unfortunately, this scenario plays out in the U.S. and Canada more than a billion times each year, especially during the spring and fall migration seasons,” says Bob Mulvihill, lead ornithologist for the National Aviary. “And research shows that even birds that manage to fly off after striking a window have less than a 50:50 chance of surviving their injuries.”

Fortunately, while bird-window strikes are a common problem, they’re also preventable. Mulvihill explains why birds fly into windows so often and what you can do to help stop birds from hitting your windows at home, so the birds that visit your yard can stay safer.

Why Do Birds Keep Flying Into My Windows?

Hearing a thud against your window and finding a bird on the ground can be upsetting, but these collisions are far more common than many homeowners realize. While skyscrapers may seem like the biggest threat, experts say most fatal bird-window strikes actually happen at homes and low-rise buildings.

“The majority of these life-ending collisions occur at low-rise commercial and residential building and homes not, as you might have expected, at the upper levels of city skyscrapers,” says Mulvihill. “This is because most birds strike windows when they are moving close to the ground in the trees and shrubbery that provide them with the food and cover they need to survive.”

The biggest culprit is the glass itself, which even the smartest birds often fail to recognize as a solid barrier in their flight path. When a bird flies into a window or hits glass at full speed, the impact can be fatal because the bird never sees the barrier in time to avoid it. This can happen with many common backyard birds, including hummingbirds, blue jays, cardinals, finches, and other songbirds that move quickly through yards with trees, shrubs, and feeders.

According to Mulvihill, there are two ways in which window glass confuses birds. The first occurs when glass is purposely installed to look like an invisible barrier for aesthetic reason. For example, outdoor glass railings, or “glass windows aligned on parallel sides of a structure, giving the see-through appearance of a tunnel.” The birds can see straight through to the other side, don’t realize there’s glass in the way, and fly towards the barrier at full speed.

The second way that glass trips birds up is by reflecting the landscape, and that issue is a lot more common with residential windows. “The combination of an expansive architectural glass building exterior and adjacent landscape plantings of trees and shrubbery can create a very dangerous ‘hall of mirrors’ for birds, especially migratory birds that settle to rest and feed in green spaces within the built environment,” Mulvill explains. “These birds may get startled and take off quickly toward what appears to them like a tunnel through a building, or reflected habitat that isn’t actually there, and when they do they often fly directly into the glass.”

Are Some Windows More Dangerous for Birds Than Others?

While any window can pose a risk, some types are more likely to cause bird window collisions than others. Large panes of glass, reflective windows, and windows positioned near trees or shrubs can be especially dangerous because birds may mistake reflections for open sky or habitat.

According to Mulvihill, most bird-window collisions happen at lower levels of buildings, where birds are flying near the trees and vegetation they rely on for food and shelter. Residential homes can be a major source of collisions because windows often reflect nearby landscaping, creating the illusion of a safe flight path.

Glass that appears invisible or allows birds to see through to the other side can also be a problem. When birds don’t recognize glass as a solid barrier, they may fly toward it at full speed, often with fatal results.

Common Bird Deterrents That Don’t Prevent Window Strikes

Both for the sake of the birds’ well-being and the structural integrity of their window glass, homeowners have plenty of reasons for wanting to prevent bird-window strikes whenever possible. But how do you do so effectively? Many homeowners search for ways to stop birds from hitting windows, but some of the most popular solutions don’t actually prevent collisions.

Many people wonder: Do window decals stop birds from hitting windows? Unfortunately, a few decorative decals spaced far apart usually aren’t enough to prevent collisions.

“A single silhouette decal of a falcon on the outside of a window, once a very popular approach, does not work,” claims Mulvihill, debunking the popular “bird decal” tactic. “A scattered few widely spaced decals of butterflies or birds doesn’t work either.” Mulvihill also advises against several other popular methods intended to scare off birds. Placing wind chimes in front of your window isn’t an effective way to prevent window strikes, he claims. Nor is putting up decoys of predators such as rubber snakes or dummy owls.

There is at least a little merit to closing your indoor shades or drapes, which is another commonly suggested bird-strike deterrent. But most people don’t want to keep their shades drawn all of the time, and Mulvihill doesn’t hold much stock in this deterrent method anyway.

“Simply pulling indoor drapes or window shades across your windows may help under some lighting conditions, but they will not remove the reflection of surrounding habitat entirely,” Mulvihill claims. “Exterior window treatments of some kind are always needed to make windows truly ‘bird safe’.”

The Best Ways to Stop Birds From Flying Into Windows

The good news is that learning how to make windows safe for birds is often simpler than homeowners realize: the goal is not to scare birds away, but to make windows visible so they recognize glass as a barrier before they fly into it. In fact, you may already even have what you need to prevent bird-window strikes at home!

“Importantly, if you already have outside window screens, then your windows are already bird safe, and you don’t need to do anything,” says Mulvihill. “Treat any other windows [or sliding glass doors] that you can see reflecting the surrounding habitat as soon as you are able. Keep in mind, most bird-window strikes occur at the lower stories of buildings, because that is the level where the birds’ habitat grows and reflects in the windows. In fact, if you have a two- or three-story house, you may only need to treat the first floor windows in order to keep your birds safe.”

If you’re in the process of building or renovating your home, Mulvihill also recommends installing proven bird-friendly glass, which is laser-etched or fritted with patterns that birds can see without obstructing your view. The National Aviary in Pittsburgh, where Mulvihill works, has been retrofitted with this type of glass in an effort to protect the birds both inside and outside its walls. Install bird-friendly glass, and you won’t have to do anything else to bird-proof your windows.

But if neither outside screens nor bird-friendly glass are an option for you, don’t worry, because there are still plenty of other cheap, easy-to-install, and highly effective window treatments you can try. The key is not to scare birds away, it’s to make the glass visible so they recognize it as a barrier before they fly toward it. These bird-friendly window solutions can help prevent collisions without changing the look of your home. Here are the ones that Mulvihill recommends:

• UV-reflective tape: In order for this to be effective, Mulvihill says that it must be applied across the entire outside surface of the window in strips no more than 2-3 inches apart. The American Bird Conservancy, which sells specialized Bird Tape, recommends several effective installation patterns.
• Bird-friendly window films: Window films don’t have to be obtrusive or block your view. Mulvihill recommends using decorative films like those from FeatherFriendly, which feature simple patterns of small dots spaced two inches apart horizontally and vertically.
• String “curtains”: Another unobtrusive method that Mulvihill recommends is to simply hang thin strings or cords outside of your window from top to bottom, spacing them 2-4 inches apart. Bird Savers also provides DIY instructions for making your own with paracord.

What to Do If a Bird Hits Your Window

If a bird flies into your window and won’t fly away, it may simply be stunned, but not seriously injured. Give it a few minutes to recover in a quiet area away from pets and people. If it remains unable to fly, appears injured, or does not recover, contact a local wildlife rehabilitator for guidance.

Knowing what to do after a bird hits a window can help give an injured bird the best chance of recovery.

Where to Place Bird Feeders to Prevent Birds From Hitting Windows

For avid birdwatchers, being mindful of where you place your bird feeders can make a world of difference.

“If you feed birds, it will help if you make sure that your feeders are either quite close to your windows (within a few feet) or else at a distance of 15-25 feet. away from them,” recommends Mulvihill. “Birds often flush away from feeders when startled or threatened by a loud noise or the sudden appearance of a predator, and if the feeders are close to the windows, then the birds will not be flying very fast if they strike into them, and so are not as likely to be injured or killed. If the feeders are more than 15 feet away from the windows, the birds are simply more likely to fly to close-by trees or bushes for shelter, rather than toward the reflection in your windows.”

By making glass easier for birds to see and placing feeders strategically away from the glass, homeowners can significantly reduce the risk of window collisions. This small change can make a big difference in protecting the birds that visit your yard.