I have also put lots of aerial barriers throughout my yard. The back yard looks like a junk yard: Wheel barrows, fence posts, tomato cages, fencing and tarps hung horizontally, 2 chicken tractors, tree branches, sections of cattle panels leaning up against other surfaces. All in an effort to deter the hawks that are calling from the trees around my yard, and doing fly overs all day long every day. I am not keeping the flock in the run... for now. I would also like to string up some CD's on fish line over that section of the yard.
in greece people put aluminium tapes to scare birds.