Birds fly into windows sometimes because they simply do not see the glass. Also, territorial male birds may see their reflections in windows and peck at otherwise try to attack what they perceive as an adversary. You can try various tactics to scare birds away from your windows to prevent them from injuring themselves or damaging the glass.
Place a fake owl near the window. Move the fake owl to a new location next to the window every three or four days so that the birds do not catch on that the owl is not real. Place the owl on a windowsill, banister, porch or other sturdy surface.
Purchase owl eyes or owl face decal silhouettes for the window to scare away the birds. Place the decals on the window panel so the birds fly away when they notice the "enemy."
Cut 2 feet of fishing line. Place the fishing line through the centre of a CD. Tie the fishing line off into a knot and hang the CD with the excess fishing line. Select a location where the CD can twirl and catch the sunlight to create a flashing light. Cut the fishing line into different lengths to hang the CDs at different levels around the window to scare the birds.
Place window decals and CDs over the windows so that they cover most of the glass. Leaving a space for the birds may not deter them from flying into the glass. Hang pieces of aluminium foil, shiny Christmas decorations or pie pans if you do not have old CDs. Install a window screen to help reduce the reflectiveness of the glass. Close the window shades or curtains to make the windows less reflective.
It is illegal to keep a migratory bird in the United States. Take an injured bird to a licensed facility.