Asking for help with Bullfrog...

Hi guys. I am new here. I need some help with figuring out what to do for a male Bullfrog that has taken up residence in my yard. I try very hard to provide food, water, and habitat for all of the creatures that visit my yard. I do not have any large body of water on my property, nor is there any such body near to me. So, I was very surprised to come out one day and find a Bullfrog swimming around inside a plastic planter drip pan. He is missing most of his left front foot, but otherwise seems fine. I felt badly for him and immediately set up the best habitat that I could on the spur of the moment. I had a kitty litter pan, and I filled it with rocks, water, and leaves for him, and tucked it in behind a shrub. He has happily lived there for a couple of months now. Yesterday, he ate a bird. Oh my. Well anyway, winter will come, and I have read that these frogs hibernate in mud during winter. Obviously, I do not have a large body of mud here. I do not want to bring him inside, but I do want to help him out for winter. What can I do? What should I do? Any suggestions would be most appreciated. Thank you so much for your time.~~Angie