Why do birds collide with windows? For birds, glass windows are worse than invisible. As they fly, they see the reflection of foliage or sky in a window, and it looks like a safe place to fly towards. The sheer number of windows in our nation makes their toll on birds huge. By some estimates, up to a billion a year may die due to window strike.
The good news is that you can greatly reduce the number of window strikes easily. Keep in mind that anything you do has to be placed on the OUTSIDE of the window to work effectively, not on the inside.