Minx,one way to slow down predator digging is to make then have to dig so far to get in,they either give up or you catch them in the act. One way of course is to bury chain link fence directly under where your wall fence meets the ground,Of course since your aviary is already in place,trying to dig a deep skinny trench under or very close to an existing fence can become a real chore.One easy way tho,is if you can locate some old chain link fence,perhaps 4' high.Use a bolt cutter and then cut the 4' width so you now have 2 pieces,each only 2' wide,,for instance if you found a 50' piece of chain link fence 4' high,splitting it in 2' would now give you 100' total. You then lay this flat on the ground as close as you can get to your outside wall fence. If you have a rainy season in the spring,if you can get this laid down,then use a lawn roller to push it into soft or wet dirt,within no time grass will be growing thru it and since it's even with the existing ground,you won't notice it by walking on it. When we built our dog kennels I rented a trencher which made setting posts with hog panel pieces stood up and cut to fit in the trench that was 2' deep. I also laid cattle panels down so there would be about 2.5' on each side of the wall-pen division fence.For a dog to dig into another run next to them,they would have to begin about 3' away from the wall fence,dig down at least 3' to get under the buried stood up hog panels,and then another 3' to be past the other cattle panel on the ground in the other pen. To dog a hole this deep,and this far would take them all day,we have not had any problems in 10 years,but I know other dog breeders that has lost dogs when a female in heat is in one pen,and another female is in the next run,,not in heat.Two littermate sisters of over 5 years old,ended when one female was in heat,and dug her way into the next run,and killed her littermate sister.Both dogs were fully titled,and very,very expensive. All there was between them was a wall fence,,if something like what I have in place was there,the owner would have been back home before any harm was done.Digging takes time,and because your blocking one spot,whatever it is will just move over 4'-5' and start digging again.If your entire perimeter extends outward 2'-3' from your wall fence,they may give up once they feel heavy wire under their digging paws.