Feathers have become enlarged and specialized and are used with or without changes of plumage colour to attract mates. The Pennant-wing Nightjar (Macrodipteryx vexillaria) acquires long pennants from the primary feathers. In the Crested Grebe (Podiceps cristatus; Podicipedidae) both sexes develop elongated chestnut-brown feathers on their cheeks, a deep brown ruff beneath the beak and a pair of horn-like tufts of glossy black feathers on the head. Sexual difference has been taken to the most extreme for any animal with the male pheasants, peacocks, grouse, manakins, and birds of paradise all of which grow feathers to a great size. The Great Argus pheasant (Argusianus argus) has wing feathers that are over a metre long and are lined with huge eye spots. The Peacock (Pavo cristatus), which is basically a pheasant, has tail feathers up to 1.8 m long, with a conspicuous pattern that resembles large eyespots.
Colouration of feathers