Kathleen
I have been thinking about barrier net -its cheaper than Electric
and they make it in green too now - it has some uv resistance.
..like this
http://www.boddingtons.us/acatalog/safety-fence-mesh.html It has big-ish holes so chicks will get through..
the bottom 1ft may need some added net with smaller holes.
Chicks will get back to the hen in most cases.
I really want to use the tractor for a shelter inside the moveable paddock.
Getting them to and from the paddocks needs some ingenuity though.
Leaving them in the tractor is not acceptable unless it is large enough.
I had a flighty , skittish, mongrel bantam once that refused to go back into the coop.
After removing it, the others calmed down and were more willing to go into their coop.
In summer I just left them to roost in the trees....
but these days they'll disappear one by one plus we need the eggs...