The gland may have a tuft of down feathers that aids in transferring the oil secretion from the gland to the bill. Powder Down - modified feathers of many birds shed an extremely fine white powder formed by the breaking of the barbule tips. These feathers may be found among the ordinary down and contour feathers, in distinct patches by themselves or both in patches and mixed with other feathers. The powder is composed of very small granules and as such is unwettable and is thus a type of waterproofing. Bristles - bristles in birds are generally feathers with a stiff shaft and barbs only on the proximal portion, if at all.
Bristles occur most commonly around the base of the bill, around the eyes, and as eyelashes.
Filoplumes are hairlike feathers that consist of a very fine shaft with a few short barbs at the end. Typically they are covered by other feathers. Filoplumes appear to function as pressure and vibration receptors - they sense the location of other feathers so they can be adjusted properly. Feather definitions and topography. Most adult birds are covered with feathers except on the beak, eyes, and feet.