Bird feathers aren’t naturally waterproof. But birds can make them water resistant by applying waxes from their preen glands. You may have watched a pet parrot grooming its own feathers – the bird will alternately rub its head against the base of its tail, and against its other feathers. It is depositing waxy, water-resistant oils found in the preen gland (at the tail base) onto the other feathers. However owl feathers are actually less water-resistant than those of many other birds.