My pen is open to the sky as it is pretty roomy, being 180 ft perimeter. I do have 3 medium size trees in there. I have heard that stringing some lines overhead discourages hawks and owls. They have really keen eyesight so they will see it and are afraid to fly in from what I have heard. I have not tried it on mine as I am still doing the fence charger installation. I do have crows about quit a bit and they always harass hawks and owls in a big way hereabouts, so I do have some protection that way. Hawks seldom get a mature bird I am told, but that does not mean they will not try! If you have a smaller run, you can buy bird netting that is used to protect strawberries and other crops. It comes in wide rolls. I suspect that it is plastic and will degrade due to ultraviolet light at some point and have to be replaced. My pen is too big to consider it, but I could do the most open parts of it. I am going to try the lines first. Probably yellow poly twine that can be bought at farm co-ops, etc.
