Why do peacocks have such colourful tails?

Charles Darwin proposed sexual selection to explain extravagant traits that seem to hinder survival. A peacock’s train, which can have over 200 feathers and span about 1.5 metres, is heavy and conspicuous, making the bird more visible to predators. But peahens consistently choose males with the most impressive displays, possibly because a large, well-maintained tail signals good health, nutrition and strong genes. The iridescent colours come not from pigments but from microscopic crystal-like structures in the feather barbules that reflect and interfere with light, producing intense greens, blues and golds. This structural colour does not fade with age.