After an aerial attack two years ago (lost one young rooster who was struck dead but not carried off) I had luck criss-crossing their moveable yard with some shiny tape. The theory is that it makes it too hard for the bird flying over to be sure it can make it back up. Big birds need a big runway? I also have an active crow group who sound the eagle/hawk alarm and harass the heck out of birds of prey. I wouldn't trust them near chicks, but they co-exist near my flocks without incident. I give them all the figs and plums that are too high to reach and they seem happy.