When faced with something like this, it sometimes helps to make a decision tree. You ask a question and if yes, go one way, if no, go another.
For example.........will birds have free access to this run at night? If yes, then anything that can get into the run can get to the birds. So you have to then account for all nocturnal predators like weasels, coons, possums, skunks, owls, etc. That is a higher standard and may even require a roof to fully protect things. An 80' x 30' run built to this standard would be expensive. The cheapest I can think of off hand might be a used chain link fence to take on the big guys, covered by hardware cloth or perhaps 1/2" chicken wire to filter out the smaller guys. (yes, they make at least 3 sizes of chicken wire).
If no, and birds will only be yarded during the day, and locked up at night, then all you have to worry about is a tight coop. That changes everything. That being the case then this run may only need to confine the birds and protect against a much smaller spectrum of predators. Maybe a 2" x 4" fence, 5' high with a hot wire on top?