Dove feather. Coloured scanning electron micrograph (SEM) of a body (contour) feather from a dove (family Columbidae). Each barb (running from lower left to upper right) has an array of barbules running from either side of it. On one side of the barb, the barbules terminate in hooks (purple) that grab the hookless barbules protruding from the next barb. This structure allows contour feathers to be strong yet light and flexible to assist in flight. Magnification: x250 at 6x7cm size.