My son and his uncle strung 450 yards of 50-lb. fishing line across the backyard, at about a height of 8 to 9 feet. We are hoping this will discourage or completely deter the local redtail hawks. One already made a visit to the backyard but the girls managed to raise a ruckus, alerting me,while they ran for the bushes and other cover.
Never tried this, but I see where it could work. I am fortunate to have dogs that will listen for and then catch hawks when they swoop in. The squirrels have figured out I am a safe zone and gathered in my yard. They must not know I LOVE squirrel and dumplings!