It's the dog owners fault. I'd be sending them a bill.
I would also say that you should not count on them to be diligent. Put up your own fence. They are completely in the wrong, but your birds are going to continue to pay for the dog owner's negligence.
I would also say that you should not count on them to be diligent. Put up your own fence. They are completely in the wrong, but your birds are going to continue to pay for the dog owner's negligence.