Daisy O’Neill’s post on Jabiru’s Prayer shows the Black-necked Stork (Ephippiorhynchus asiaticus), “kneeling” – although the so-called knees bend backward, as compared to ours bending forwards.
Lena Chow sent in an image of a Greater Adjutant (Leptoptilos dubius) that shows it “kneeling” or a reverse kneel, as she calls it, and a link to the blog, Bill of the Birds, that gives an explanation as to why the bird rests that way (left).
As Bill Thompson explains, birds are actually tip-toeing around. Birds walk on their toes. These toes are attached to the end of the long tarsometatarsus, which is actually formed by the fusion of the tarsals and metatarsals. In humans, the tarsals or ankle bones and metatarsals, the foot bones at the ends of which are attached the toe bones, are short and not fused.
So what we assume as the bird’s knee, the joint that bends backwards, is actually equivalent to our ankle. The bird’s knee is one level up, next to the body. So the stork is actually resting on its heels.