Can Birds See Glass? (All You Need To Know)

Birds have exceptionally good eyesight. Birds of prey such as eagles and falcons have eight times the vision of humans, and owls have a specialized lens at the back of their eyes that helps them see at night. Although vision is generally better than humans, birds are often injured or killed by flying through glass, which begs the question, can birds see glass?

Birds don’t learn visual cues that tell the brain that an object is glass—glass is a human invention, after all. Birds also have fundamentally different vision than ours — it’s very acute, but they perceive depth differently than mammals. Also, birds can misinterpret reflections in glass like the sky and trees, mistaking them for the real thing.

In fact, most animals don’t understand glass until they have the opportunity to learn it, just like humans – we are not born with the ability to perceive and understand glass. Modern glass is also so transparent that even humans can walk through it from time to time, it’s no wonder birds make the same mistake when flying at high speeds.

Read on to discover more interesting facts about how birds perceive glass.

bird looking at reflection outside window

Why do birds fly in windows?

Most birds seem to be very sensitive to their surroundings, so we often have to keep an appropriate distance when observing them in the wild. If you get too close to the birds, their keen eyes will spot you and fly away. The next time you see a bird, observe how large its eyes are relative to its body, and therefore relative to its brain—this is part of why birds have such keen eyesight. Not only do birds have large eyes, but their eyes are densely packed with receptors for improved vision and other adaptations, such as extra lenses to reflect more light.

Still, millions of birds are killed every year by flying into windows, so it’s a relevant question to consider why birds are so bumbling with windows and glass.

There are several explanations. First, birds’ eyes are often mounted on the side of their heads to maximize their field of view, but at the expense of depth perception.

In contrast, human eyes point straight ahead, which means that each eye’s field of view overlaps, which enhances depth perception at the expense of our field of vision. This means that birds may not be able to perceive the depth of 3D structures that contain glass, such as buildings.

Birds can also see and perceive darker colors and see them more intensely than humans. Birds often mistake their own reflection for another bird, possibly because their perception of the reflected color is strong enough to mistake it for the real thing. So when birds see reflections of the sky, trees, etc. in windows and glass, they may look realistic.

Perhaps the most important factor is that birds don’t learn glass in their natural environment — it’s not part of their “curriculum,” so to speak. Given the chance, birds and other animals will learn to sense glass.

A blue tit wrestles with its own reflection outside the window

How to Stop Birds From Flying in Windows

Glass manufacturers now produce bird-resistant glass for use on the exterior of towers and other tall buildings to prevent bird kills and glass damage. Bird safety glass enhances the UV reflection that birds see strongly, thus helping birds see the glass as a barrier rather than just a continuation of their environment.

DIY methods include blacking out windows as much as possible, moving plants away from windows, and putting large decals or posters on windows. You can also buy “bird-proof film,” which is a film designed to go over the top of windows—they’re popular in new eco-friendly homes and have other benefits, such as filtering excess infrared light.

Zen curtains are another DIY method that uses string run across a window to signal to birds that the window is impassable.

what to do if a bird hits your window

If you see or hear a bird hitting your window, check to see if there are other birds lying on the ground nearby. If they are relatively unharmed, they will most likely fly away immediately.

Is the bird alive or injured?

If the bird was lying motionless on the ground, it could be stunned, injured or killed. First, check for obvious injuries, such as cuts or breaks. If you suspect an injury to a wing, leg or other body part, please contact your local wildlife hospital. If the bird does not appear to be injured but is not moving, it may have been stunned or may have been killed by impact.

To check if a bird is stunned or dead, look for its beak to open and for signs of breathing. If you put two fingers on its chest, you might even be able to feel its heartbeat. If you can’t feel the bird’s breathing or heartbeat, don’t assume it’s dead, as these slow down considerably when the bird is stunned. Put it in a box and wait to see if it recovers, or call a wildlife hospital for advice.

Is the bird dizzy?

Stunned birds are basically knocked out or concussed and need to be given time to recover safely. If you think the bird is stunned, place it in a warm, dark box with some cushioning. A stunned bird may take 2 to 3 hours to recover.

Starling looking at the reflection outside the window

Can a bird die if it hits a window?

Considering the speed at which birds often fly when they strike windows, many birds are not immune.

The exact number of how many birds die each year from window collisions is unknown. One oft-quoted figure is one billion, derived from a 1990 paper by biologist Professor Daniel Clem in the Journal of Field Ornithology.

The British Trust for Ornithology estimates that around 100 million bird collisions occur in the UK each year, of which about a third can be fatal.

These are only estimates, but they can still tell the story, especially in cities that intersect certain bird migration routes. Spring was considered the worst time for bird collisions due to migratory behavior, and high-rise buildings were by far the worst collision events compared to standard 2-story houses.