Fake, molded plastic "decoy" owls are a popular way of deterring common pest species of bird, such as woodpeckers and pigeons. According to the New York Times, fake owls are even used to deter birds near airport runways. Decoy owls work, at least temporarily, because owls prey on many species of birds.
The idea behind decoy owls is a straightforward one. Several species of owls prey upon other bird species, and so their mere presence deters those birds from remaining in the area if they think they have spotted an owl. When a prey sees an owl-like figure, they will usually find somewhere else to be.
Although decoy owls can be effective at deterring many species of birds, they are only a temporary fix. According to the Cornell Lab of Ornithology, birds quickly get used to seeing the same thing day after day, and no longer fear it because it is not moving and thus seems less threatening. When this happens the birds will return, sometimes after just a few days.