@ct_bergstrom my husband and I befriended an injured Common Raven in the Duluth Zoo many years ago. We began playing a sort of "pass the stick" game with it through the bars of its cage. It clearly came to recognize us and would bring a stick to the bars of the cage whenever we saw it. I don't know how many zoo visitors it had trained in this way, but we were thrilled to be able to share some fun with it whenever we saw it.