Why Birds Can’t See Glass And How To Protect Them

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Up to a billion (yes, billion!) birds die every year in the United States from collisions with glass doors and windows. This is because birds are unable to see glass and try to fly straight through it, leading to their untimely deaths. Luckily, you can easily your local birds by making a few changes to your home’s glass windows. 

Birds have difficulty seeing glass because they don’t know how to identify it. They don’t understand reflections and have very poor depth perception. Luckily, you can easily protect birds by installing bird-safe glass, using curtains, and placing bird feeders closer to your windows. 

Modern glass is extremely clear — so much so that even humans sometimes walk straight into it accidentally. So, it’s no wonder that birds also make this mistake while flying at extremely high velocities. Let’s look at exactly why birds fly into glass and what you can do to protect them, so you that don’t have to worry about having any bird fatalities on your conscience.

Why Do Birds Fly Into Glass?

Home window with Easter paper cuttings

Birds usually seem to be very aware of their surroundings, which is why we usually maintain a suitable distance when we observe them in the wild. Along with having large eyes, birds also have countless receptors in their eyes, which enhance their visual acuity and reflect more light. 

Despite their extremely sharp vision, many millions of birds (some studies say up to a billion) still die due to window collisions every year, which begs the question: Why are these creatures so clumsy when it comes to glass windows?

There are actually several reasons why birds fly into glass: 

Birds Don’t Understand Reflections 

When birds see reflections of vegetation, landscape, or even the sky, they think they’re seeing the real thing. They don’t have any concept of a reflection like we do, so they fly straight into a reflective object, believing that they’ll be able to fly safely through it. 

This is especially true for perfectly clear reflections rather than amorphous and blurred ones.

Birds Don’t Know How to Detect Glass

In some cases, even humans can be easily tricked into thinking that a reflection is the real thing. When we identify reflections on glass, it’s usually because of the cues we’ve learned as ways to identify glass.

Mullions (vertical bars between panes of glass) and small cracks help us detect glass, but since birds never learn how to perceive glass, they usually fly straight into it. 

Birds See a Wider Depth of Color

Birds see and perceive colors more intensely than mammals, which means that reflections look much fuller and richer to them than they look to the human eye. 

This essentially means that birds pick up so much color from reflections that they believe them to be the real thing, even though we perceive reflections as being dim and much less colorful. 

Birds Have Very Poor Depth Perception

Most birds have eyes on the sides of their heads. This gives them a wider field of vision but sacrifices their depth perception, which is a phenomenon that comes with eyes that are in the front or facing the same direction. 

This means that birds don’t always understand how far away an object is, and, as a result, they’re much more likely to crash, especially when they’re flying at full speed. 

Birds Don’t Have a Concept of Vertical Reflective Surfaces 

While we commonly use glass in windows and doors, it’s important to remember that glass like this doesn’t actually exist out in nature. In fact, you won’t even find anything similar to glass in the natural habitat of a bird.      

Birds routinely see reflections in water but aren’t as confused by it because they know they’ll find water at ground level. On the other hand, glass doors and windows are completely unique concepts to them, as they’re both reflective and vertical.

Birds Are Usually Panicked When They Collide With Glass

Another big reason why birds fly into glass is that they’re flying in a panicked state. Like humans, birds also find it more difficult to focus when they’re panicked. 

Whether there’s a sudden loud noise or a nearby predator, they fly away from any possible threats as quickly as possible, which unfortunately leads to collisions. 

Where Can You Find Bird-Safe Glass?

Most glass manufacturers make bird-safe glass, which is now commonly being used on tower blocks and other tall buildings to prevent both bird fatalities and any potential damage to the glass itself. 

Bird-safe glass basically enhances the UV reflections that birds see so clearly, which helps them perceive the glass as an obstacle or barrier, and not simply a natural part of the environment. Methods like silk screening and fritting are also used to create a pattern in the glass and break its reflectivity, alerting birds to its presence.  

The price of bird-safe glass is usually only about 5% higher than that of regular glass. However, if you don’t want to spend the extra money, bird collisions can also be limited by constructing buildings in such a way that the glass is slightly angled slightly downwards. This will prevent clear reflections of the skyline on the glass and will protect birds from crashing into it.  

The Best Ways to Protect Birds From Flying Into Your Glass

Along with installing bird-safe glass, there are a few other ways you can protect birds from flying into the glass windows of your home: 

Install Window Decals or Tape Strips

Window decals and clings, like this one from Rabbitgoo (on Amazon), help prevent birds from seeing any reflections in the glass. A colorful window decal can enhance the aesthetics of your window. 

You can also attach tape strips to the outside of your window to make it appear more solid and less of a continuation of the environment. 

Place Bird Feeders Near the Window

It’s advisable to place bird feeders within two feet of your windows, so the birds slow down as they come closer to the glass. Also, try not to put houseplants very close to your windows, as they may attract birds and increase the chances of a collision.

Use Curtains or Shutters

Modern windows with uv curtain and light brown house wall from outside view

Using shades or curtains will help make your windows appear more solid. It’s better to keep your shutters closed when the windows aren’t in use as well.

You can also apply a one-way film (on Amazon) to the exterior of your windows. This will make the glass more visible to birds, but will still remain transparent to you. This film will reduce any incoming infrared radiation as well, and will subsequently lower your summer cooling costs.   

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