Feathers are epidermal growths that form unique shells or feathers on birds and other extinct dinosaur species. They are considered to be the most complex exodermic structures found in vertebrates and the first example of complex evolutionary novelty. They are one of the characteristics that distinguish existing birds from other creatures.

Although feathers cover most parts of birds, they only come from certain well-defined areas of the skin. They help to fly, insulate and waterproof. In addition, coloring helps communication and protection. Featurology (or feather Science) is the name of the science related to feather research.

Feather is one of the most complex outer skin appendages found in vertebrates. It is formed in the epidermis or in the outer layer of the epidermis. The β - keratins in feathers, beaks and claws, as well as claws, scales and shells of reptiles are composed of protein chains that are hydrogen bonded into β - folded sheets, and then further twisted and cross-linked through disulfide bonds to form β - keratins of mammalian hair, horns and hoofs that are stronger than their structures. However, it has been found that the transcription factor cdermo-1 can induce feather growth and leg scales.

Feathers protect birds from water and cold. They can also be picked in rows to provide insulation for eggs and young eggs. Single feathers in wings and tail play an important role in controlling flight. Some species have feathers on their heads. Although feathers are very light, because many bones are hollow and contain air bags, birds' feathers are twice or three times heavier than their skeletons. Color patterns camouflage birds' predators in their habitats, and animals in foraging animals. As with fish, the top and bottom colors may vary to provide camouflage during flight. Significant differences in feather patterns and colors are part of the sexual dimorphism of many birds, and are particularly important in the selection of pairings. In some cases, even if no color difference is found in the visible range, the UV reflectance of feathers of different genders will be different. The wing feather of the male Club wing flower man machaeropterus deliciosus has a special structure, which can be used to produce sound through ear piercing.

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