I had a most bothersome Woodpecker that decided to poke a hole in the siding of my house and start building a nest in the insulation. I grabbed my $25 Red Ryder BB gun and from the corner of the house put a copper ball on his butt. I know what it feels like to get shot with that gun, and while it won't penetrate the skin, it will definitely sting and raise a welt. I doubt it has enough power even at close range to kill a bird the size of a pigeon except for an ideal head shot. Certainly anything within 30 yards is well within the accuracy capabilities of the little carbine. As a pest deterrant, it is one of the best I can think of. If you are worried about what an inadvertent BB might do, then they also have those wonderful soft pellet guns that don't have nearly the range but will do a good job, or even a paint gun.

In fact, shoot paint balls from your slingshot and your errant shots should also diminish.