I like a 12 gauge with #8. Even if they are way out of range a good blast and dusting encourages them to find a safer area. My mentality is to associate my place with danger to them so they will go somewhere else. On the other black birds, I think they are starlings. I use a 22 with low velocity shorts or cci cb rounds. They are only good for 30 yards or so but are silent. I have a pellet rifle but it scares them off when it's shot. They are more persistent. The only way I found to get rid of them is death. They are just in small groups though.
Buying chickens will lessen the food source for birds. If you get a hardy breed they can survive on what's there and not cost you any more on the feed bill. This will also cut out a lot of the food source for mice and rats which also spread disease.