Blow gun or some other quiet method of pigeon control

[JimmyLyding]

Earlier tonight, I discovered that the local pigeons have been hanging out on top of my Weber kettle grill, and strategically depositing what they deposit right through the vent holes onto the cooking surface. Luckily I had a backup cooking surface.
However, I'm looking for a very-lethal method of convincing those rats-with-wings that they don't want to hang out in my yard. It must be quiet so as to not arouse my neighbor's ire if they are the types to become upset, and I doubt that they would. Blowgun? Pellet gun? Trained bobcat? I've culled pigeons with a blowgun back in college @ the U of A, but the local police didn't like it. Actually, they had no problem with it, but the crazy lady who lived across-the-street from our fraternity house did have a problem.
Any suggestions?

[JimmyLyding]

My neighborhood has a problem w/ feral cats. I guess back in the day a lot of people would dump unwanted kitties in Encanto Park and Phoenix College. The city comes around every few years, and sterilizes as many of them that they can catch. Unfortunately they seem to be more interested in grackles and songbirds than pigeons. I'm going to try a squirt gun filled with white vinegar as I've been told it's effective.
I'm not even sure predators seem to make much of a difference. My mom lives a block from the Phx Mountain Preserve, and hears coyotes on a daily basis, but still has a pigeon problem even after I installed some plastic spikes.