There is a special gland that produces oil near the duck's tail which spreads and covers the outer coat of the duck's feathers, making it water-proof. Beneath the water-proof coat are fluffy and soft feathers to keep the duck warm. Ducks keep clean by preening themselves. They do this by putting their heads in funny positions and putting their beaks into their body. They preen themselves very often.
Ducks give out a special sound.
Listen to the sound of ducks quacking here. However, not all ducks quack. Ducks were once wild until they were domesticated by the Chinese many hundreds of years ago. There are still many different species of wild ducks. It is harder to tell a male from a female with the Pekin ducks because they look almost the same.