Only the male birds of paradise have the wonderful plumage, rich colours and patterns that we associate with the species. The females are very drab and dull by comparison, which is a good clue as to the function of the male bird's finery.
He uses it to display to females to attract them for mating. The male bird uses his plumage to the greatest effect by performing in an extraordinary way as well. He perches on a branch in a tall forest tree, then sends out a very mournful cry to attract the female's attention. He then grasps the perch with his feet and topples slowly backwards until he is hanging upside down. He then jigs about, flashing his feathers.
The male birds with the best feathers and best acting performance attract females the most effectively – they mate and then the female is left to hatch the eggs and bring up her brood alone. The male goes off to another branch to attract another female with a new display. The most brightly coloured birds are the most promiscuous.