Feathers that are arranged in regular rows on a bird's body, giving the body its streamlined shape. Each has a central horny shaft (the rachis) with a flattened vane on each side. Each vane is composed of two rows of filament-like barbs, which are connected to each other by means of hooked barbules to form a smooth surface. There is often a small second vane, the aftershaft, near the base of the feather.
Subjects: Biological Sciences.