Talk:Raven Branwen/@comment-26286858-20150706100743/@comment-24891101-20150714225333

It's technically a uropygium, containing the pygostyle, formed from the fusion of final caudal vertebrae, to which the rectrices attach. So yes, it's not technically a tail, but neither you nor I are ornithologists. In common parlance, the uropygium and the rectrices are collectively called a bird's tail. The existence of the word tail-feather should be evidence of that.

If an avian faunus were to possess a coccyx which was more reminiscent of a pygostyle and likewise possess some form of rectrices, then depending on their conformation, it may very well be difficult to sit down in chairs, since the pseudopygostyle would likely curve away from the body, and neither the pygostyle nor the rectrices are particularly flexible, though they would likely be mobile. Consider a chair: for humans, 270 degrees are blocked, and any stiff protrusion would make sitting difficult, whereas a flexible tail like Sun's causes only slight discomfort, rather than making sitting near-impossible, and has sufficient utility to not require docking.