Birds have a waterproof covering of feathers.
Feathers are both watertight and airtight, as well as waterproof.
Birds have a special gland near their tail. The gland, called the uropygial gland or preen gland, produces oil that makes the bird’s feathers waterproof.
When a bird, particularly a waterfowl (aquatic bird), preens itself, it distributes the oil from the gland onto its feathers with its beaks. Preening is the act of cleaning the feathers, but also ensuring that there is enough oil on the feathers to waterproof them.
Watertight and airtight feathers occur because the feathers are overlapping. This overlapping pattern on a bird’s body exposes the waterproof feather tips, and allows water to roll right off the bird’s back. The oil is clear-coloured or light-coloured, so usually people cannot see it.
People know that the bird has waterproof feathers because little drops of water beads appear on the bird’s feathers and body.
If a bird is unable to keep its feathers waterproof, it can become waterlogged and helpless. This occurs during oil spills (from businesses and burst oil pipes, and other oil spillages in the water and sea). The black oil covers the feathers and the bird cannot fly.
So, waterproof feathers help the bird to swim and to fly.
Waterproof feathers also insulate a bird from cold temperatures.
Photographer: Martina Nicolls
Martina Nicolls: SIMILAR BUT DIFFERENT IN THE ANIMAL KINGDOM