Hawks

Got a pair of Swainson's hawks in the area that are doing a good job of corralling the pigeons to one area. When the hawks are flying around the pigeons all flock together and leave the premesis. Swainson's hawks are primarily insect eaters, so they aren't feeding on the pigeons, but the pigeons are still frightened away. Based on this, I believe they will respond to any raptor, wether or not they are a direct threat. So, a nesting box for any raptors you may have in the area will do well to rid you of some pigeons.

I have not noticed a response to owls, however. In my area we have the smaller species, but they don't respond to their presence at all. Larger owls may be effective.