The peacock is the classic example of sexual selection because males display an elaborate ornamental tail.
In common usage, “peacock” refers to the male peafowl, while females are peahens and the species as a whole is called peafowl. During courtship, a male raises and fans his long upper-tail coverts, producing the familiar eye-spotted display. Female choice can favor traits that improve mating success even when those traits carry survival costs.
Charles Darwin used peafowl plumage as a major example in The Descent of Man, published in 1871. He argued that ordinary survival advantages could not fully explain such conspicuous ornaments and developed his theory of sexual selection to account for them.
Sexual selection is a form of natural selection involving differences in mating success. It can result from mate choice or competition among members of the same sex, and it does not always produce dramatic ornaments.