The uropygial gland secretes an oil (preen oil) through the dorsal surface of the skin via a grease nipple-like nub or papilla. The oil contains a complex and variable mixture of substances formed greatly of aliphatic monoester waxes, formed of fatty acids and monohydroxy wax-alcohols.
The uropygial gland produces an oily secretion (preen oil) from the dorsal skin surface via a grease nipple-like structure. This secretion contains a complex mixture of substances primarily composed of aliphatic monoester waxes, made up of fatty acids and monohydroxy wax-alcohols.