Donkey is domesticated in China mainly for the hide, as there are traditional snacks made from e-jiao, which is donkey hide gelatin. It is also used in herbal medicine.
As for bird's nest it is harvested in South East Asia and popular amongst females in China as it is thought to be good for the complexion. It has been consumed for centuries in China and is quite expensive, so in some places it might not be real bird's nest.