We originally planned to close in part of our one-acre garden/orchard so that the chickens could free range in it. Then we realized that we have way too many birds of prey around here- all of them- hawks, owls, eagles, etc. We talked about trying to set up overhead netting but we decided not to, for a couple of reasons. One, the effort and expense, and two, we like to hang out in our garden and enjoy it, and our chickens. We don't want to feel like we are in the middle of a prison or a chicken concentration camp just to keep our flock safe.
What we ultimately did was to make a 5' wide chicken moat down one end of the space. We actually never got it all the way down that one side- we did maybe 2/3 of the way and decided that was good for the number of birds we had at the time. That also allowed us to park a portable coop at the end of the moat for shelter.
We had an existing 7' high, seven wire high tensile electric fence around the entire acre to keep deer out. We also had some second hand chain link fencing that is 4' high, so we ran that on the inside of the posts for the electric fence and then did a second run parallel and 5' across from the first run. To prevent aerial predators from getting into the moat we installed a 8' tall post at one end of the moat and then ran a strand of fishing line from the post to the roof of the chicken coop, right down the middle of the moat. After that we added two more lines, parallel to the first one, about a foot on each side of it. All three lines are above head height so we can walk around in the moat if we need to, and the best part is, they are pretty much invisible unless one is actually looking for them. Birds of prey will not fly through them to get to the chickens. In fifteen years we have not lost a single bird.
The chickens have plenty of room to run around foraging, and we don't have to worry about losing them. We also don't have to put up fencing to keep them out of the garden because the moat serves that purpose. I would eventually like to add to the moat until it goes completely around the entire acre, but that is a lot of work for something that we don't really need. But maybe someday.