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.
Feathers are the one most distinguishing characteristic of birds.
The central shaft of a feather has two sections. The calamus, the naked portion of the shaft, is implanted in a socket in the skin. Beyond the calamus is the rachis, that bears branches called barbs, on its side. The barbs on either side of the rachis constitute the vane. The vanes are symmetrical on most body feathers but asymmetrical on flight feathers of the wing and tail.