>>12391260Dancing in animals like birds is usually a various mix of
>Showing off different parts of your bodyIt could be exposing various colors or showing the size of your wings or the luster of your feathers. Physical characteristics which require additional investment from the body show that the individual is in good shape
>Showing characteristicsEndurance, strength and intelligence can all be measured by various dances or other mating rituals
>Establishing dominanceLot of dances are somewhat mock battles either directly composing of fighting moves or at the very least a non violent way of showing which male is the strongest which is useful since it serves the function of a battle without causing damage to the participants.
etc.
Lot of good reasons really.