First of all we live across from a small lake where hawks are always flying around looking for food.  Until we had chickens we enjoyed seeing the large hawks swooping around. We have our chickens in our backyard fenced in by a large 6' fence and they free range all day.  We had thought that our chickens were to large to interest the hawks but one day my husband was out in the yard working on the coop roof and a large hawk swooped down and grabbed on of our large bodied full grown hens.  My husband jumped off the roof to scare the hawk and the hawk just turned it's head and basically did not care and proceeded to attack the hen.  Not until my husband actually kicked at the hawk did it fly away.  Well after keeping all then hens in for about a week we thought that the hawks would have found a new hunting spot but low and behold we would see them sitting in the trees and on top of the neighbor's houses just eyeing the hens.  So, a friend of ours gave us 2 3D rubber/plastic wolf / coyote  decoys.  We planted them in a couple of spots in the hen's roaming area and did not have a single hawk attack or problem for over 2 1/2 years!!  One day my son took them down to mow and forgot to put them back up.  Well, not more than 5 days later we lost 2 of our hens to hawks.  So, I am saying in our experience, the wolf decoys WORK!!  Needless to say, our wolf / coyote decoys never are allowed to leave the yard!!