I found a carport for a good price that's 10' x 20' and 8' tall. My plan is use the frame and drape chicken wire up and over. Then connect the chicken wire to the existing fence. If that works out I'll have to post pictures.
While chicken wire will turn birds of prey, don't count on it to stop a coon from crawling up and tearing through. Still have to be vigilant about buttoning them up tight in coop at dark.