I wanted to fiddle with ideas for an avian anthro form I made for myself a while back, and stuck for a pose, I came up with sort of a sprawled out yawn/stretch. I'm not entirely happy with it, but the result is certainly satisfactory. Some experiments with muscles here too.
The head is a combination of three different birds, eagle/vulture/falcon, which by the way, it's not easy to find good pictures of yawning.