Request #56

I’ve been searching for a book i read in the 70’s possibly 80’s. I think the book cover had a hunter and a deer or stag on it. The book starts out with a man walking through or hunting in the woods and he ends up in another world or dimension. He meets a wizard or magician and at the end of the book the wizard turns himself into the deer or stag and sacrifices himself for the hunter in exchange for his help when they were in the other world.   Update: Tsuga’s Children by Thomas Williams, solved by Lost Classics reader Marion