Powder-Down Zones

(in Russian, pudretki), small areas on the skin of certain birds, such as herons, bustards, toucans, and parrots, covered with powder down, the barbules of which are distinguished by their softness and fragility. When they decompose, they form a dustlike substance that covers the plumage and partially replaces the lubrication of the feathers with the secretion of the preen gland, which is usually reduced in birds with highly developed powder-down zones.