The skin covers the body and produces feathers and a variety of other external structures: beak covering, wattles, comb, scales of feet and legs. The skin is thinner than mammals’ and attaches to the skeleton in a number of places: skull, beak, wrist, wing tips, dorsal side of the pelvis, tarsometatarsus, and toes. The general function of the skin is protective, the base of external features, and serves as a large sensory organ with receptors for temperature, pressure, and vibration. One or two glands at the base of the tail (uropygial glands) produce fatty secretions.