page_title: Indian peafowl
section_title: Sexual selection
hierarchical_section_title: Indian peafowl / Behaviour and ecology / Sexual selection
caption_attribution_description: English: Common Peafowl: male courting female. Pavo_cristatus.
context_page_description: The Indian peafowl, also known as the common peafowl, and blue peafowl, is a peafowl species native to the Indian subcontinent. It has been introduced to many other countries.
  The male peacock is brightly coloured, with a predominantly blue fan-like crest of spatula-tipped wire-like feathers and is best known for the long train made up of elongated upper-tail covert feathers which bear colourful eyespots. These stiff feathers are raised into a fan and quivered in a display during courtship. Despite the length and size of these covert feathers, peacocks are still capable of flight. Peahens lack the train, and have a greenish lower neck and duller brown plumage. The Indian peafowl lives mainly on the ground in open forest or on land under cultivation where they forage for berries, grains but also prey on snakes, lizards, and small rodents. Their loud calls make them easy to detect, and in forest areas often indicate the presence of a predator such as a tiger. They forage on the ground in small groups and usually try to escape on foot through undergrowth and avoid flying, though they fly into tall trees to roost.
context_section_description: The colours of the peacock and the contrast with the much duller peahen were a puzzle to early thinkers. Charles Darwin wrote to Asa Gray that the "sight of a feather in a peacock's tail, whenever I gaze at it, makes me sick!" as he failed to see an adaptive advantage for the extravagant tail which seemed only to be an encumbrance. Darwin developed a second principle of sexual selection to resolve the problem, though in the prevailing intellectual trends of Victorian Britain, the theory failed to gain widespread attention.
  The American artist Abbott Handerson Thayer tried to show, from his own imagination, the value of the eyespots as disruptive camouflage in a 1907 painting. He used the painting in his 1909 book Concealing-Coloration in the Animal Kingdom, denying the possibility of sexual selection and arguing that essentially all forms of animal colouration had evolved as camouflage. He was roundly criticised in a lengthy paper by Theodore Roosevelt, who wrote that Thayer had only managed to paint the peacock's plumage as camouflage by sleight of hand, "with the blue sky showing through the leaves in just sufficient quantity here and there to warrant the author-artists explaining that the wonderful blue hues of the peacock's neck are obliterative because they make it fade into the sky."
  
  In the 1970s a possible resolution to the apparent contradiction between natural selection and sexual selection was proposed. Amotz Zahavi argued that peacocks honestly signalled the handicap of having a large and costly train. However, the mechanism may be less straightforward than it seems – the cost could arise from depression of the immune system by the hormones that enhance feather development.
  The ornate train is believed to be the result of sexual selection by the females. Males use their ornate trains in a courtship display: they raise the feathers into a fan and quiver them. However, recent studies have failed to find a relation between the number of displayed eyespots and mating success. Marion Petrie tested whether or not these displays signaled a male's genetic quality by studying a feral population of peafowl in Whipsnade Wildlife Park in southern England. She showed that the number of eyespots in the train predicted a male's mating success, and this success could be manipulated by cutting the eyespots off some of the male's ornate feathers.
  Although the removal of eyespots makes males less successful in mating, eyespot removal substantially changes the appearance of male peafowls. It is likely that females mistake these males for sub-adults, or perceive that the males are physically damaged. Moreover, in a feral peafowl population, there is little variation in the number of eyespots in adult males. It is rare for adult males to lose a significant number of eyespots. Therefore, females' selection might depend on other sexual traits of males' trains. The quality of train is an honest signal of the condition of males; peahens do select males on the basis of their plumage. A recent study on a natural population of Indian peafowls in the Shivalik area of India has proposed a "high maintenance handicap" theory. It states that only the fittest males can afford the time and energy to maintain a long tail. Therefore, the long train is an indicator of good body condition, which results in greater mating success. While train length seems to correlate positively with MHC diversity in males, females do not appear to use train length to choose males. A study in Japan also suggests that peahens do not choose peacocks based on their ornamental plumage, including train length, number of eyespots and train symmetry. Another study in France brings up two possible explanations for the conflicting results that exist. The first explanation is that there might be a genetic variation of the trait of interest under different geographical areas due to a founder effect and/or a genetic drift. The second explanation suggests that "the cost of trait expression may vary with environmental conditions," so that a trait that is indicative of a particula
caption: Male courting female
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