I think the fact that the bird
belonged to someone is enough to at least fine the guy. After all, these are not wild, native birds, they are exotic and are connected to people through ownership.
I had a weasel after my birds two nights ago, and believe me, you don't want to know what I would do to that weasel, be it four-legged or two-legged!
Must be getting feeble in old age. I took it that the birds were free ranging. If they were someones property then burn the guy for rustling.