Filoplumes are hairlike feathers distributed inconspicuously throughout the plumage in association with contour and flight feathers. They monitor the movement and position of vaned feathers. They are most numerous near mechanically active or moveable feathers; flight feathers may have eight to twelve filoplumes per quill. Filoplumes consist of a fine shaft that thickens distally, ending in a terminal tuft of one to six short barbs with barbules.