The peacock, either the Indian or green peafowl, demonstrates the process of evolutionary adaptation through the long, brilliantly colored tail feathers of the male. Adaptation is the process by which a trait that confers a particular advantage for survival develops over time. The male peacock, Darwin postulates, evolved the adaptive trait of the tail feather display to compete for a mating partner.
Because female peacocks, or peahens, choose male peacocks with larger tail feather displays as ideal mating partners, that adaptive trait becomes reinforced and further reproduced in the gene pool. In Darwin's terms, the peacock's tail is an adaptive trait that demonstrates sexual selection. A male peacock's tail feathers can be up to 6 feet long, far longer than his 2-foot long body. The feathers are iridescent blue, green and purple, with distinctive eye shapes near the tips.
The eye shape can be considered another adaptive trait. When threatened, the male peacock raises and spreads his tail feathers. The display makes the peacock appear larger, while the eyes can trick a predator into thinking that more than one peacock appear in front of it. Because the weight and size of his tail compromise his mobility, his survival depends on tricking predators in exactly that manner. The continued survival of long-tailed peacocks supports Darwin's theories of adaptation and sexual selection.