Turkey and White-fronted Goose (Anser albifrous) pygostyle
2.24" (58 mm) L and 1.9" (50 mm) L
Shown here are the pygostyles of a white-fronted goose and a turkey. A pygostyle is the fused caudal (tail) portion of the vertebral column. This group of vertebral bones carries the tail feathers and controls the movements that are important in flight. Pygostyles are present in most groups of birds, though they are generally absent in large ratites (large flightless birds), except for the ostrich (where its presence suggests that ostriches are descended from flying ancestors).
Several vertebrae are fused to form a terminal bone that is shaped somewhat like a plow blade. This is the basal point of attachment for the stiff tail feathers. The spinal cord does not extend into the pygostyle; rather, connective ligaments and muscles along the pygostyle control the movements involving the tail feathers.
On top of the pygostyle is an oil-filled, globular-shaped gland which has a duct that opens to the exterior of the skin. This gland is called the preen uropygial gland. Birds tweak the gland with their beaks to collect oil and wipe it on their plumage to provide waterproofing and feather protection.
The fleshy portion of a pygostyle, including the preen gland, on a cooked fowl is a commonly eaten tasty portion popularly referred to by farm families in the past as the "pope's nose".