Last updated on May 11th, 2023 at 11:59 pm
Up to one billion birds in the United States die every year due to collisions with glass windows. This is because birds can’t see the glass, and they try to fly right through it.
The reasons why birds can’t see glass are:
1. Reflections Vs. Reality
When birds see the reflection of a landscape, vegetation, or sky, they think they see the real thing.
They don’t understand the concept of reflection, so they’ll keep flying right into a reflective object, thinking that they can fly right through it.
This is especially true when reflections are clear rather than blurred and amorphous.
2. Glass Detection
Humans can just as easily be tricked into thinking a reflection is reality in some cases.
And when we can’t, it often has to do with the cues we’ve learned as ways of detecting glass.
Small cracks and mullions show us that we’re looking at glass, which we expect to see and know to look for when navigating buildings.
3. Intense Color Vision
Birds see color more intensely than mammals do, which means that when they see a reflection, it looks much richer and fuller than it looks to the human eye.
Essentially, this means that birds pick up enough color from a reflection to believe that it’s the real thing, even though we see the reflection as dim and less colorful.
4. Poor Depth Perception
Most birds have an eye on each side of the head.
This gives them a wild field of vision but sacrificing depth perception, which comes from two eyes facing the same direction.
This means that they have a more difficult time than we do understanding how far away an object is.
So when they’re flying full speed and see a window, they’re more likely than us to crash.
5. Vertical Reflective Surfaces
Glass, as we use it in doors and windows, doesn’t exist in nature. There is nothing quite like glass in a bird’s natural habitat: nothing vertical and reflective.
They see reflections in water routinely but aren’t confused because they expect to find water on ground level.
Glass windows and doors are unique in that they stand upright.
6. A Panicked State of Mind
Another major reason why birds can’t see glass is that they are flying in a panicked state.
Birds, like humans, have a more difficult time focusing when they’re panicked.
Whether it be due to a nearby predator or a sudden loud noise that they think could be a predator.
They try to fly away from threats quickly, and unfortunately, this often means collisions.
7. Lighted Window Attraction
Birds can crash into lighted windows for several reasons.
Nocturnal birds, such as migratory songbirds, are attracted to bright lights at night because they use stars to navigate, and artificial lights can interfere with their ability to orient themselves.
Some birds may be disoriented by the contrast between bright indoor lights and the dark outdoor environment, causing them to fly into windows.
Birds may mistake lighted windows for open sky, especially if they are flying at high speeds or in poor weather conditions.
Lighted windows can also reflect nearby trees or other vegetation, creating the illusion of a clear flight path.
Finally, birds may be attracted to the warmth radiating from a lighted window, especially during cold weather, and may fly towards the window in search of shelter.
How To Protect Birds From Hitting Your Windows and Doors
You may wonder whether there’s anything you can do to make collisions between birds and your glass windows and doors less likely to happen.
Thankfully, there are many things that you can try, ranging from the expensive to the simple and DIY.
The things that you can do to protect birds from hitting your glass windows and doors include the following:
- Install bird-safe glass. Bird-safe glass has distinct reflective patterns due to fritting, silk-screening, or ultraviolet coatings, breaking up the reflections seen by birds without noticeably changing the appearance of the glass to human eyes. Bird-safe glass is quite effective but also tends to be very expensive.
- Install window decals. A cling like the Rabbitgoo Privacy Window Film from Amazon.com prevents birds from seeing tempting reflections in your glass. This cling, in particular, has the appearance of colorful rainbows to add to the aesthetic of your window as well.
- Make sure that your bird feeders are close to your windows. Placing the feeders within one and a half feet of a window will make the birds slow down as they fly near the glass.
- Use curtains or shades. These will make it easier for the birds to see the windows as solid.
- Don’t put houseplants near windows. They can attract birds and make collisions more likely to happen.
- Install a screen a few inches outside your window. This will make your window more visible, and it will ensure that any impacts that do happen are less severe.
- Use shutters. Keep them closed when your windows aren’t in use.
- Draw on the windows with soap or paint. Leaving patterns on the glass will make the reflection less clear and, therefore, less confusing.
- Use chart tape strips. These can be attached to the outside of the window to make the window appear more solid.
- Use blinds. Keep them at least halfway closed whenever possible.
- Turn off the lights at night. Or, close the curtains or blinds to hide the light.
Can Birds Learn To Detect Glass?
If a bird survives a collision into a piece of glass, the chances are that it will remember not to fly through the same piece of glass again.
This is especially true if it happens multiple times.
However, birds cannot learn to generalize about windows, glass doors, or other clear reflective obstacles.
Why Do Birds Crash Into Glass More in the Spring?
There are two primary reasons why birds crash into glass windows and doors more often in the springtime.
One is that springtime is the peak mating season, and two is that springtime is the beginning of migration season.
Birds crash into glass more during the mating season.
This is because courting males will see their reflections as competing birds and attack, flying straight into the glass on purpose.
During migration season, birds crash into glass more often because they’re on the move for months at a time.
And many regions see more bird activity during this time in general.
You’ll see this pattern mirrored in the fall when migration season is ending.
In the summertime, there are fewer collisions.
But young birds who are just flying for the first time at this time of the year are especially likely to crash as they explore new environments for the first time.