Feathers are one of the most prominent features of a bird's anatomy, and they are unique to birds.
Every bird has feathers and everything that has feathers is a bird . Feathers perform a number of functions for a bird. It is believed by most scientists that this insulating effect was the primary force driving the evolution of feathers, i.e. ancestral birds developed feathers to keep themselves warm. Feathers also protect birds from UV light. Secondly, feathers allow for flight.