A range of short brown stiff feathers, about six inches long, fixed in the uropygium, is the real tail, and serves as the fulcrum to prop the train, which is long and top-heavy, when set on end.
"The-Natural-History-of-Selborne"
White, Gilbert
It is found that in preparing specimens there is a practically uniform place for cutting off from the body the uropygium with attached feathers, and this is exactly where the tail bends back at an angle to the body in the fresh bird.
"The Subspecies of the Mountain Chickadee Vol. 17, No. 17, pp. 505-515"
Joseph Grinnell