Window Alert WFWA Window Alert Leaf

Window Alert is a static-cling decal that may be applied to outside of window glass. The decal contains a component which brilliantly reflects ultraviolet sunlight. This ultraviolet light is invisible to humans, but glows brilliantly for birds. 4 stickers per package. For maximum protection, scientific studies suggest placing decals 2 inches horizontal by 4 inches vertical, from one another.

The Birdhouse suggests that you will need more than you think. Anything more that 2" square, can look like fly throughable space to a bird.