A few years back (2007 to be exact), we posted a clip from David Attenborough's nature documentary series "Planet Earth" featuring the amazing mating display of one particular species of bird of paradise (if you haven't seen it before, go see it, it's definitely worth it), the superb bird-of-paradise (Lophorina superba), native to the rainforests of New Guinea, where the male displays to the female what looks like an iridescent smiley face.
In the following video, the Lab of Ornithology at Cornell University, as part of their "Birds of Paradise Project", very neatly explains how the male superb bird-of-paradise achieves its magnificent transformation.
(source)
