we also have the starlings and they are much worse than the blackbirds even though they are quite smaller. They move in, in the spring and don’t leave until fall and try to nest everywhere, especially in the gazebo above the hot tub & under the deck cover by the front door. Nasty little creatures and nothing we have tried thus far hinders them.
Could be African Swallows...generally non migratory though.
Much as I hate to say it...a BB gun works great! The coyotes clean up the carcasses.