On your acre, use a few tall 2 x 4s (12' -16'), run mason twine to each other (up to 100-150' apart)and hang a few CDs up there. It really puts on a light show. Our 2 hawks, which live 700' from our coop, have not returned to visits our girls since I put them up. Knock on wood. Inexpensive and quick. Just attach them to T-posts with some wire. Goes up very quickly.