Which gland helps penguins waterproof their feathers during preening?

The uropygial gland helps penguins waterproof their feathers during preening.

Also called the preen gland or oil gland, the uropygial gland is located near the base of a bird’s tail. Penguins spread its oily secretions across their feathers with their bills. This regular preening helps maintain feather condition and contributes to the waterproofing and insulation essential for life in cold water.

Penguin feathers form a dense outer covering that traps air and limits heat loss. Keeping that covering in good condition is especially important because damaged or poorly maintained feathers can reduce insulation and increase the energy cost of swimming and thermoregulation.

The uropygial gland is different from the salt glands above a penguin’s eyes. Salt glands remove excess salt from the bloodstream, whereas the uropygial gland produces material used during feather maintenance. Penguins also replace their entire feather coat in an annual catastrophic molt.