Wouldn't be surprised if there was some falconry activity. Some birds-of-prey can be taught to target certain species. Most airports use falcons or other birds of prey to keep large waterfowl away from the planes. I have not heard of any being used to target rock doves, but sounds plausible.
I don't know if he's for hire, but I spotted this fine fellow while on the Mark Twain. He looks a bit plump don't you think?