Using a fake owl is an effective way to keep birds away from gardens, patios and windowsills. However, Cornell Lab of Ornithology explains that birds may gradually acclimate to a stationary or nonmoving visual stimulus, making it necessary to periodically change the location or appearance of the decoy owl.
An owl is a natural enemy of most birds, and the appearance of one often spooks birds into leaving an area
A decoy owl that mimics a real one in appearance, sound or movement often produces the best results. Some visual deterrents for birds feature rotating heads that move in the breeze and require no batteries or power, while others have scary eyes, realistic heads and large wings that spread out, imitating a flying predator.