Window Alert is a static-cling decal that may be applied to home and office windows. The decal contains 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 a humans.Window Alert decals help birds "see" windows and thus avoid striking the glass. Protects both indoor and outdoor birds.Select Butterfly, Hummingbird or Leaf pattern.