I would suggest having one end '3-sides-boxed-in', using steel siding or thinnish plywood or the like. (Alternatively you *could* use a tarp, but it will shred itself during the season and you'll have to replace it over and over, plus it is not as protective).
Reasons:
-somewhere to get out of the wind
-somewhere to get out of the rain
-somewhere to get out of the sun/heat
-somewhere to get away and hunker down if menaced by predators pacing the mesh part of the walls
Unless you can get really heavy gauge chickenwire, and *I* sure don't know where to get it around here, I would suggest you consider 1" welded wire mesh instead. Even during the daytime, a lot can happen...
If you put them out in the tractor before getting 1 egg from each and every hen, I'd just put a portable nestbox in there with 'em, just in case. I have a couple of rubbermaid totes that I cut a hole in the end, or you could maybe find an old covered-style cat litter box at a garage sale or thrift store.
Have fun,
Pat