uropygial

The uropygial gland, also known as the preen gland, is a sebaceous gland located at the base of the tail in most bird species. It produces an oily secretion that birds spread on their feathers during preening, helping to condition and protect plumage.

Anatomy and secretion are characteristic features of the gland. It is typically a holocrine gland with a duct that opens at the uropygial orifice near the base of the tail. The secretion is rich in lipids, including wax esters, fatty acids, glycerides, and alcohols. The exact composition varies among species and can change with diet, season, and reproductive state.

Functions of the uropygial secretion are diverse. Preening distributes the oil across the feathers, helping to maintain flexibility and waterproofing, reduce wear, and preserve the plumage’s appearance. The secretion can influence the feather microbiome and may deter certain parasites and pathogens. Some components have antimicrobial properties, contributing to feather health, though the effectiveness can depend on the bird and its environment.

Variation exists across birds. The gland is present in the majority of species, but in a few lineages it is reduced or absent. Gland size and secretion composition can be linked to ecological factors such as habitat, climate, and lifestyle, including aquatic or aerial lifestyles.

In research and ecology, the uropygial gland is examined for its chemical diversity, functional roles in feather maintenance, and implications for avian health, signaling, and evolutionary biology.