Oil

A bird needs to look after its feathers. It keeps them clean and tidy by preening, which means running its beak through the feathers, a bit like a human combing their hair.

The bird picks up oil from a special preening gland at the base of the tail, and the protective oil is then spread through the feathers with the beak. This oil keeps the feathers waterproof, as well as keeping each feather in shape and protected from dirt.

The oil gland is very well developed in birds that spend time in the water, because they need extra protection from the water.