I knew someone who covered their entire run with thin wire with gaps about the length off your hand. He never had problems with hawks, but terrible problems with foxes. They either took them when they were not in the run but on his property, or when he forgot to shut the coop. Those foxes just always knew, when they could take a chicken. Day or night .
No fox has ever got a chicken from me, thank goodness, but I have had hawks take a handful of chicken in the three years I've been keeping them. They took a young one, a couple of weeks ago again. My roosters stopped them taking a hen, she survived but was injured but they couldn't care less about the young ones I guess. I've got masses of bushes and trees here, so they've really got to learn to run and hide.