To Know How to Prevent Birds from Flying Into Windows? Bird-window collisions are a common problem that can injure or kill birds and leave homeowners distressed. Fortunately, there are several simple and effective ways to prevent birds from flying into your windows. One of the most effective strategies is to make the glass visible to birds. Since birds often mistake reflections of the sky or trees for open space, applying window decals, stickers, or patterns can help. Place them closely together—ideally 2 inches apart vertically and 4 inches apart horizontally—to be truly effective.