If you feed the birds near your windows or glass doors or even if you don't and the glass is near where they fly, you have probably had a bird dash against the glass. They often do not survive. I love watching the birds up close from my kitchen table but often I would have to go out and rescue a stunned little bird. I saw the perfect solution one day at our "everything for a dollar" store. Little metal butterfly stickers. I popped them onto my glass doors and no more knocked out birds! They make the glass visible to my little feathered friends.They have held up through lots of window washes and of course, since they are on the inside, rain is not an issue.