Although birds can be distinguished from other vertebrates by a number of anatomical details such as keeled breastbones, feathers are by far the best known and most visible feature unique to birds. All birds have feathers and no other animal possess them at all. Refer to the paragraph below and the fact sheets included in this page to help you guide this discussion. Feathers are unique structures made of keratin, the same protein that is the basic material of our hair and fingernails. Flight is usually the most important and obvious function of feathers but they also play vital roles in thermoregulation, concealment from predators and displays to attract mates and repel rivals.
Flight feathers make up the aerodynamic surfaces of the bird's wings and tail.
Contour feathers cover the bird's body and are important in aerodynamics, insulation and coloration. Down feathers usually lay below the contour feathers and function primarily as insulation. There are several other specialized types of feathers including some that act as vibration sensors like whiskers. Wrap up your discussion by reinforcing key points. One useful way to accomplish this is to ask students to compare the functions of feathers with those of hair, the unique feature of mammals.