WindowAlert is a window decal that may be applied to home and office windows. The decals contain a component which brilliantly reflects ultraviolet sunlight. This ultraviolet light is invisible to humans, but glows like a stoplight for birds. Birds have vision that is up to 12 times better than that of humans. WindowAlert decals, and our new UV Liquid, help birds see windows and avoid striking the glass. All collections have 4 stickers except the Leaf Medley which comes with 5 stickers.