uropygialis

The uropygial gland, also known as the preen gland, is a small sebaceous gland found in birds. Located near the base of the tail, it secretes an oily substance that plays a crucial role in maintaining the health and functionality of feathers. The term "uropygial" derives from the Greek words *oura* (tail) and *pygē* (rump), reflecting its anatomical position.

This gland is particularly prominent in many bird species, including ducks, geese, and songbirds. The secretion produced by the uropygial gland is rich in lipids, waxes, and proteins, which birds use to coat their feathers during preening. This process helps to waterproof feathers, enhance insulation, and protect against parasites and pathogens. The oily substance also contributes to the feather’s flexibility and structural integrity.

The uropygial gland is not present in all bird species, with some exceptions such as ostriches and penguins, which lack this structure. In birds that possess it, the gland is typically paired with a specialized feather, the uropygial feather, which aids in spreading the secretion during grooming. The secretion’s composition can vary slightly among species, reflecting adaptations to different environmental conditions.

Beyond its role in feather maintenance, the uropygial gland may also serve social functions. Some birds use the secretion in territorial displays or courtship rituals, though this is less common than its primary role in feather care. The gland’s importance underscores its evolutionary significance in avian physiology and behavior.