We have EVERYTHING in dog kennels...geese, ducks, chickens. We are right beside a 600 acre park, so we have fox, possum, raccoon, hawks....who knows what else.
We have some of our pens with extra panels on top. Other pens are covered with welded wire fence zip tied very securely. On others, we took PVC pipe and made frames that are 4' wide and 10' long and then we have zip tied wire around them, and secured them to each other and the sides of the kennel. So far, I think that the welded wire is probably the most secure. We have to pull it VERY tightly so it doesn't sag, but even a little sag seems to be OK.
We love our kennels and we use baling twine from the hay to tie them together since we are often moving them around as we change things. I hadn't considered just making a long row like a dog kennel, but I bet that would make things more secure. However, it would mess up my method of giving them all separate running areas during the day.
We use Little Tikes houses and cedar dog houses, a couple of plastic dog houses, as shelters for the birds. During the day, we open the kennels and let the geese go out and run around all day. I haven't done it yet with the ducks or chickens because I am not sure about getting them back in at night. LOL. Guess that will be next on my To Do list.