I use welded wire on my outer runs but I do have some large dog kennel/chain link runs ones too. They are my favorite! The birds I see the most in our runs stealing food here are cardinals.I use 1" x 2" welded wire. It is expensive enough! I have been told by people who live in the city that wild birds (mostly English sparrows) will go through the 1" x 2" wire and thieve food. So if keeping wild birds out is also a priority, I'd go with 1"x1". I am lucky that the English sparrows don't favor the more open desert areas like where I live and I haven't had a problem with birds going through my 1" x 2" wire.