I worked as a steeplejack in my younger days back east. We used a specific caulking in nesting areas that stuck to their feet and feathers or an aluminum stripping that was like razor wire that prevented them from nesting. These methods were used because we couldn't poison them or shoot them in the locations we serviced.
One of the funniest things I remember was a pastor asking me if the caulking really worked and a pigeon landing close to us with wings gunked up from the caulking. That answered his question.