Thay also like to have more than one roost.
That way they have a choice of the most secure roost, and best chance to thwart any potential invader/attacker.
Is there any bird feeders nearby? If there is maybe they need to be taken down for a few weeks. Like an earlier post said the squirrels go after the bird seed and the crows see the extra activity. And as far as the Bird Bangers we buy ours from a company call Oesco, they have a website Oklahoma Electrical Supply Company
It would be raining soup, and id be be standing outside with a fork