Research topic: Feather

feathers outgrowths of the skin, constituting the plumage of birds. Feathers grow only along certain definite tracts (pterylae), which vary in different groups of birds. Feathers develop from tiny projections of tissue (papillae) embedded in follicles and nourished by blood vessels in the dermis. ...

Component structure of the outer covering and flight surfaces of all modern bird s. Unique to birds, feathers apparently evolved from the scales of birds' reptilian ancestors. Like hair, feathers are made of keratin , a fibrous protein. They are variously specialized for insulation, flight, ...