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Can Birds See Glass? Or Why Do They Fly Into Windows?

can birds see glass?

Can birds see glass? Many of us wonder this because, sadly, we see birds fly into windows. Such “window strikes” can happen wherever reflective glass is located near vegetation.

These accidents occur at houses, places of business, and many other buildings. They can also happen any time of the year, but migration is one of the worst times for window strikes.

In fall and spring, hundreds of beautiful birds die from window strikes, especially as they migrate through cities. See below to learn about this problem and what we can do to prevent it!


Why Do Birds Fly Into Windows?

Birds fly into windows for a couple of main reasons. When a window acts as a mirror, instead of seeing glass, birds see a bush, tree, shy, or other reflection.

They fly headfirst into the window because they believe they are flying to vegetation or up into the sky.

When a window is clear and has potted plants on the other side of the glass, a bird hits the window because it believes it is flying to those plants. Or, even if windows lack plantings, a bird might think it is flying into a house to escape a predator.

can birds see glass?

Either way, the bird flies into and hits the window. It might be alright if it flutters into the window, but when birds hit the glass at their typical speed, they usually end up dying. Even if a bird is stunned and then flies away, tragically, most still succumb to brain bleeds or other internal injuries.

At night, migrating birds can also fly into windows. In this case, warblers thrushes, and other birds are attracted to buildings with illuminated rooms. For unknown reasons, they see lights, fly towards them and end up hitting windows in apartment and office buildings.


How To Stop Birds From Flying Into Windows?

Sadly, window strikes take a huge toll on birds. One study in 2014 estimated that one billion birds in the USA may die from hitting windows each year! These terrible numbers have an impact on a wide number of species, especially small migrants.

Related: What does seeing a dead bird mean?

Fortunately, we do have solutions, including easy changes we can make in our own homes. The first step is to go outside and find which windows are the biggest threat to backyard birds.

From the garden, we can look at our windows, especially big ones, and see if any reflect vegetation or sky. Birds see those same reflections and are more likely to fly into those windows.

How to stop birds from flying into windows

The next step is bird proofing” our windows. Basically, we need to put decals, stickers, or other objects on the entire exterior of the glass. No matter which deterrent technique we use, vertical markings should be placed less than four inches apart, and horizontal markings should be less than two inches apart.

Although hawk stickers have often been used, sadly, these don’t work unless many are spaced close to each other. Although birds might avoid a single raptor sticker at first, they quickly learn that the shape is not an actual threat.

In addition to stickers, we can also use soap, tempura paints, and tape to create patterns and other markings. Another popular solution uses long, closely spaced pieces of rope that hang in front of the window. These “zen curtains” are easy and can be an eye-pleasing way to save the lives of dozens of birds.

Additional effective solutions to keep birds from hitting glass include mosquito screens and netting installed on the outside of the window. Netting installed three inches from the glass prevents collisions with the window.

Yet another solution is using transparent film that allows people to see out of the window but makes it look solid or opaque from the outside. Since this solution diminishes the light that enters through the window, it can also lower our cooling needs.

To prevent nocturnal migrants from hitting buildings in cities, we can also support “lights out” initiatives. These measures encourage building owners to turn off the lights in buildings at night during migration. They also promote the installation of downward-facing lighting.


Frequently Asked Questions

What do birds see when they see glass?

Birds see what the glass reflects. If glass acts like a mirror and shows a reflection of a tree, birds see and believe they are flying to a tree and not into glass.

Why can’t birds see windows?

Birds do not see windows because window glass is transparent. Birds don’t see the glass itself. They only perceive what is reflected in the window, or what is on the other side of the window.

Can birds see you through a window?

Yes, but only if the window doesn’t show a reflection. Birds see through windows, but they do not perceive the glass. This means that if they see a potted plant on the other side of a window, they may fly into the glass, thinking they are just flying to that plant.

Can a bird fly into my window at night?

Yes. Sadly, during nocturnal migration, birds are attracted to lit windows and die when they fly into them. This mostly happens in apartment buildings.

What to do if a bird flies into a window?

If a bird flies into a window, put it in a box and keep it in a dark, cool place. After 15 minutes, take the box outside. If the bird does not fly away and appears injured, bring it to a professional wildlife rehabilitator as soon as possible.

About the Author

Patrick O'Donnell

Patrick O'Donnell has been focused on all things avian since the age of 7. Since then, he has helped with ornithological field work in the USA and Peru, and has guided many birding tours, especially in Costa Rica. He develops birding apps for BirdingFieldGuides and loves to write about birds, especially in his adopted country of Costa Rica.

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