Or you could try the solution used by ...oh, shoot, what's his name, he played one of the originals in M*A*S*H and was the dad in "Steel Magnolias"...
At any rate, in order to rid his home of grackles prior to his daughter's wedding, Dad takes a cross bow and ties about a zillion firecrackers to it, lights the firecrackers, and then shoots the cross bow into an upper branch of the tree.
The birds took off when all those firecrackers went off at once all around them.
Seriously though...shotshells? That's safer than a .22 because they won't travel a mile....
Springmom