My hens roam about 1/2 an acre out of 5. I did the twine and bird netting by pounding poles on the perimeter of where they run and then put netting every so often to break up the space. It isn't foolproof but it works pretty well. Hawks were taking a good size duckling every day and injured...
I ran sisal twine crossing back and forth across an eighth of an acre and draped bird netting over parts of it. It's been month and they were taking a duckling every day when i decided to do it