It is thought that filoplumes on the wings associate with receptors that offer automatic feedback to and from the nervous system, adjusting feather position to contribute most efficiently towards flight. Bristles are a specialized feather type consisting of an elongate, tapering rachis, sometimes with a few short barbs near the base. They are generally restricted to the head and are tactile. Bristles can be seen on the heads of vultures and on the faces of many species. They cover the nostrils of crows and woodpeckers.
Specialized bristles form the eyelashes of birds that have eyelids.
Bristles found around the mouths of birds are called rictal, and they, too, are thought to be tactile. Birds that chase insects through the air with open mouths, especially nightjars, are thought to use the bristles as a funnel. Because flycatchers capture insects by snapping their bills on them, the function of their rictal bristles is not clear. Most birds waterproof their feathers by applying oil gland secretions to them while preening. Powder down grows throughout life, and it disintegrates near the feather tips.