Some look like aviaries.

But since I am in a rural area, I need to safeguard against other critters like snakes, raccoons, who may pose a problem. I agree that it could be a trap for birds so perhaps a smaller wire would be a deterrent.
on edit: I am bookmarking this great post for those interested in catios.

You could put bricks around the bottom maybe. Here's mine. (I don't have to deal with snakes.)