|Male Indian peacock on display. The elongated upper tail coverts make up the train of the Indian peacock.|
Peafowl include two Asiatic species (the blue or Indian peafowl originally of India and Sri Lanka and the green peafowl of Burma, Indochina, and Java) and one African species (the Congo peacock native only to the Congo Basin) of bird in the genus Pavo and Afropavo of the phasianidae family, the pheasants and their allies, known for the male's piercing call and, among the Asiatic species, his extravagant eye-spotted tail covert feathers which he displays as part of a courtship ritual. The male is properly called a peacock, the female a peahen, and the immature offspring peachicks. The adult female green peahen is coloured similarly to the male, whilst that of the Indian and African varieties is dull grey and/or brown. Peachicks of both sexes vary in colour between yellow and tawny usually with patches of darker brown or light tan and "dirty white" ivory.
The Indian peacock has iridescent blue and green plumage. The peacock tail ("train") is not the tail quill feathers but the highly elongated upper tail covert feathers. The "eyes" are best seen when the peacock fans its tail. Both sexes of all species have a crest atop the head. The Indian peahen has a mixture of dull grey, brown, and green in her plumage. The female also displays her plumage to ward off female competition or signal danger to her young.
The even more splendid green peafowl differs from the Indian peafowl in that the male has green and gold plumage with black wings with a sheen of blue. Unlike the Indian peafowl, the green peahen is similar to the male, only having shorter upper tail coverts, a more coppery neck, and overall less iridescence.
The Congo peacock male does not display his covert feathers but uses his actual tail feathers during courtship displays. These feathers are also much shorter than those of the Indian and green varieties, and the ocelli are much less pronounced.
Occasionally peafowl appear with white plumage. Although albino peafowl do exist, this is quite rare and almost all white peafowl are not, in fact, albinos: they have a genetic mutation called leucism which causes an overall reduction in pigment which, in peafowl, causes a complete lack of pigment in their plumage but still leaves them with blue eyes; by contrast, true albino peafowl have a complete lack of melanin and therefore have white plumage but also an albino's characteristic red or pink eyes. Leucistic peachicks are born yellow and become fully white as they mature.
As with many birds, vibrant iridescent plumage colours are not primarily pigments, but structural colouration. Optical interference Bragg reflections based on regular, periodic nanostructures of the barbules (fiber-like components) of the feathers produce the peacock's colours. Slight changes to the spacing of these barbules result in different colours. Brown feathers are a mixture of red and blue: one colour is created by the periodic structure and the other is created by a Fabry–Pérot interference peak from reflections from the outer and inner boundaries. Such structural colouration causes the iridescence of the peacock's hues since interference effects depend on light angle rather than actual pigments.
Evolution and sexual selection
||This article should be divided into sections by topic, to make it more accessible. (December 2014)|
Charles Darwin first theorized in On the Origin of Species that the peafowl's plumage had evolved through sexual selection. This idea was expanded upon in his second book, The Descent of Man and Selection in Relation to Sex.
The sexual struggle is of two kinds; in the one it is between individuals of the same sex, generally the males, in order to drive away or kill their rivals, the females remaining passive; whilst in the other, the struggle is likewise between the individuals of the same sex, in order to excite or charm those of the opposite sex, generally the females, which no longer remain passive, but select the more agreeable partners.
Sexual selection is the ability of male and female organisms to exert selective forces on each other with regard to mating activity. The strongest driver of sexual selection is gamete size. In general, eggs are bigger than sperm and females produce fewer gametes than males. This leads to eggs being a bigger investment, and therefore to females being choosy about the traits that will be passed on to her offspring by males. The peahen's reproductive success and the likelihood of survival of her chicks is partly dependent on the genotype of the mate. Females generally have more to lose when mating with an inferior male due to her gametes being more costly than the male's.
There are multiple hypotheses that explain the evolution of female choice. These hypotheses include direct benefits to the female. In some instances, females are provided with benefits such as protection, shelter, or nuptial gifts that sway the female's choice of mate. Another possible hypothesis is that females choose mates with good genes. Males with more exaggerated secondary sexual characteristics, such as bigger, brighter peacock trains, tend to be more fit and therefore have better genes in the peahen's eyes. These better genes will directly benefit her offspring as well as her fitness and reproductive success. Runaway selection also seeks to clarify the evolution of the peacock's train. In the case of runaway sexual selection, linked genes in males and females code for sexually dimorphic traits in males and preference for that trait in females. The linkage disequilibrium of the genes causes a positive feedback loop that exaggerates the trait in males and the preference in females. Another hypothesis for the evolution of female choice is sensory bias, in which females have a preference for a trait in a non-mating context that becomes transferred to mating. It is important to remember that there may be multiple causations for the evolution of female choice.
Work concerning female behavior in many species of animals has sought to confirm Darwin's basic idea of female preference for males with certain characteristics as a major force in the evolution of species. Females have often been shown to distinguish small differences among potential mates and to prefer mating with individuals bearing the most exaggerated characters. In some cases, those males have been shown to be more healthy and vigorous, suggesting that the ornaments serve as markers indicating the males' abilities to survive and, thus, their genetic qualities.
The peacock is perhaps the best-known example of traits believed to have arisen through sexual selection, though in recent years this theory has become the object of some controversy. It is known that male peafowl erect their trains to form a shimmering fan in their display to females. 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 tails. Females lost interest in pruned males and became attracted to untrimmed ones. Further testing revealed that males with fewer eyespots, and thus with lower mating success, were more likely to suffer from greater predation. Even more interestingly, she allowed females to mate with males that had variable numbers of eyespots and reared the offspring in a communal incubator to control for differences in maternal care. Chicks fathered by more ornamented males weighed more than those fathered by less ornamented males, an attribute generally associated with better survival rate in birds. When these chicks were released into the park and recaptured one year later, those with heavily ornamented feathers were found to be better able to avoid predators and survive in natural conditions. Thus, Petrie's work has shown correlations between tail ornamentation, mating success and increased survival ability in both the ornamented males and their offspring.
Furthermore, peafowl and their sexual characteristics have been used in the discussion of the causes for sexual traits. Amotz Zahavi used the excessive tail plumes of male peafowls as evidence for his "Handicap Principle". Considering that these trains are obviously deleterious to the survival of an individual (due to the more brilliant plumes being highly visible to predators and the longer plumes making escape from danger more difficult), Zahavi argued that only the most fit males could survive the handicap of a large tail. Thus, the brilliant tail of the peacock serves as an indicator for females that highly ornamented males are good at surviving for other reasons, and are, therefore, more preferable mates. This theory may be contrasted with Fisher's theory that male sexual traits, such as the peacock's train, are the result of selection for attractive traits because these traits are considered attractive.
However, some disagreement has arisen in recent years concerning whether or not female peafowl do indeed select males with more ornamented trains. In contrast to Petrie's findings, a seven-year Japanese study of free-ranging peafowl came to the conclusion that female peafowl do not select mates solely on the basis of their trains. Mariko Takahashi found no evidence that peahens expressed any preference for peacocks with more elaborate trains (such as trains having more ocelli), a more symmetrical arrangement, or a greater length. Takahashi determined that the peacock's train was not the universal target of female mate choice, showed little variance across male populations, and, based on physiological data collected from this group of peafowl, do not correlate to male physical conditions. Adeline Loyau and her colleagues responded to Takahashi's study by voicing concern that alternative explanations for these results had been overlooked, and that these might be essential for the understanding of the complexity of mate choice. They concluded that female choice might indeed vary in different ecological conditions.
Merle Jacobs proposes a food-courtship theory, which states that females are attracted to males due to features that resemble territorial foods. He claims peahens are attracted to peacocks due to the resemblance of their eye spots to blue berries. It has been also suggested that peacocks' display of colourful and oversize trains with plenty of eyespots, together with their extremely loud call and fearless behavior, have been formed by the forces of natural selection (not sexual selection), and served as an aposematic warning display to intimidate predators and rivals.
The large proportion of success in copulations for peacocks lies in the plumage of colours of the males' eyespots and the angle in which they are displayed. In a study conducted by Roslyn Dakin and Robert Montgomerie, it was shown that the ocelli illuminated in specific angles during male courtship proved to be a major factor in the triumph of a peahen's decision to choose them whilst other males. The correct angle in which their colours are shown to be more illuminated allows for the female to become more attracted to the male even if they contain a smaller train and less ocelli than other peacocks.
Different parts of the train may suggest different interests for peahens as well. In an experiment directed by Jessica L. Yorzinski, the eye movements of peahens were carefully watched whilst they chose which mate they decided to copulate with. As a result, it was found that the peahens would shift their eye sight from the peacocks display, to their surrounding environment, to different parts of the peacock's train throughout the display from the male. The lower train is usually evaluated during close-up courtship and the upper train is more of a long-distance attraction signal. It was also found that actions such as train rattling and wing shaking also kept the peahens attention. This suggests that the evolution of a variety of different display components increases the chance that a male will win over a peahen's attention. This study overall suggests that female cognitive progress and selective attention plays an essential role in sexual selection in this species.
Although an intricate display catches a peahen's attention, the Redundant Signal Hypothesis also plays a crucial role in keeping this attention on the peacock's display. The Redundant Signal Hypothesis explains that whilst each signal that a male projects is about the same quality, the addition of multiple signals enhances the reliability of that mate. This idea also suggests that the success of multiple signaling is not only due to the repetitiveness of the signal, but also of multiple receivers of the signal. In the peacock species, males congregate a communal display during breeding season and the peahens observe. Peacocks first defend their territory through intra-sexual behavior, defending their areas from intruders. They fight for areas within the congregation in order to display a strong front for the peahens. Central positions are usually taken by older, dominant males, which influences mating success. Certain morphological and behavioral traits come in to play during inter and intra-sexual selection, which include train length for territory acquisition and visual and vocal displays involved in mate choice by peahens.
In courtship, vocalization stands to be a primary way for peacocks to attract peahens. Some studies suggest that intricate song played whilst birds displayed prove to be impressive to females, whereas other studies show high call rates to be more successful. Singing in peacocks usually occurs either before, after, or sometimes during copulation. Alerting other males of mating may function to reduce interference or to synchronize breeding times. Vocalizations by birds suggest many characteristics of a male that demonstrate attractiveness to a female. One of these includes the signaler's ability to avoid certain costs associated with producing the call itself. Intrinsic costs reflect the fitness of the male and his ability to take time away from other activities such as foraging. Extrinsic costs are those in which the male is able to produce this signal even considering the predation risk. Vocalization is a highly risky process for males since it draws attention to him from predators. However, if a male is able to still vocalize and survive, it suggests his overall his fitness. At times, the repetition of vocalization to attract females can cause significant energy costs as well for peacocks. The recurrence of vocal tactics to attract females is also a display of the male's stamina, which in turn proves one's overall fitness to the peahen. Another method of peacocks to display vocal cues to impress peahens becomes apparent in the cumulative assessment model proposed by Payne (1998). This model is mainly exclusive to aggressive competitions rather than courtship and is displayed when a female challenges a male physically in order to test his fitness. If he is successful in withstanding her personal attacks towards him, he is deemed worthy of mating.
|Problems playing this file? See media help.|
Peafowl are forest birds that nest on the ground but roost in trees. They are terrestrial feeders. All species of peafowl are believed to be polygamous. However, it has been suggested that peahens entering a green peacock's territory are really his own juvenile or sub-adult young and that green peafowl are really monogamous in the wild.
Ancient Greeks believed that the flesh of peafowl did not decay after death, and it so became a symbol of immortality. This symbolism was adopted by early Christianity, and thus many early Christian paintings and mosaics show the peacock. The peacock is still used in the Easter season especially in the east. The 'eyes' in the peacock's tail feathers symbolise the all-seeing Christian God and – in some interpretations – the Church. A peacock drinking from a vase is used as a symbol of a Christian believer drinking from the waters of eternal life. The peacock can also symbolise the cosmos if one interprets its tail with its many 'eyes' as the vault of heaven dotted by the sun, moon, and stars. By Christian adoption of old Persian and Babylonian symbolism, in which the peacock was associated with Paradise and the Tree of Life, the bird is again associated with immortality. In Christian iconography the peacock is often depicted next to the Tree of Life.
In Hindu culture, the peacock is the mount of the lord Kartikeya, the god of war. A demon king, Surapadman, was split into two by Karthikeya and the merciful lord converted the two parts as an integral part of himself, one becoming a peacock (his mount) and another a rooster adorning his flag. The peacock displays the divine shape of Omkara when it spreads its magnificent plumes into a full-blown circular form.
Even though the peafowl is native to India, in Babylonia and Persia the peacock is seen as a guardian to royalty, and is often seen in engravings upon the thrones of royalty. The monarchy in Iran is referred to as the Peacock Throne. Melek Taus (ملك طاووس—Kurdish Tawûsê Melek), the "Peacock Angel", is the Yazidi name for the central figure of their faith. The Yazidi consider Tawûsê Melek an emanation of God and a benevolent angel who has redeemed himself from his fall and has become a demiurge who created the cosmos from the Cosmic egg. After he repented, he wept for 7,000 years, his tears filling seven jars, which then quenched the fires of hell. In art and sculpture, Tawûsê Melek is depicted as a peacock. However, peacocks are not native to the lands where Tawûsê Melek is worshipped.
In Hellenistic imagery, the Greek goddess Hera's chariot was pulled by peacocks, birds not known to Greeks before the conquests of Alexander. Alexander's tutor, Aristotle, refers to it as "the Persian bird". The peacock motif was revived in the Renaissance iconography that unified Hera and Juno, and which European painters focused on. One myth states that Hera's servant, the hundred-eyed Argus Panoptes, was instructed to guard the woman-turned-cow, Io. Hera had transformed Io into a cow after learning of Zeus's interest in her. Zeus had the messenger of the gods, Hermes, kill Argus through eternal sleep and free Io. According to Ovid, to commemorate her faithful watchman, Hera had the hundred eyes of Argus preserved forever, in the peacock's tail.
In 1956, John J. Graham created an abstraction of an eleven-feathered peacock logo for American broadcaster NBC. This brightly hued peacock was adopted due to the increase in colour programming. NBC's first colour broadcasts showed only a still frame of the colourful peacock. The emblem made its first on-air appearance on 22 May 1956. NBC later adopted the slogan "We're proud as a peacock!" The current version of the logo debuted in 1986 and has six feathers (yellow, orange, red, purple, blue, green). On account of the association between NBC and peacocks, it is sometimes nicknamed the "Peacock Network".
A stylized peacock in full display is the logo for the Pakistan Television Corporation.
In some cultures the peacock is also a symbol of pride or vanity, due to the way the bird struts and shows off its plumage.
During the Medieval period, various types of fowl were consumed as food, with the poorer populations (such as serfs) consuming more common birds, such as chicken. However, the more wealthy gentry were privileged to more exotic foods, such as swan, and even peafowl were consumed. On a king's table, a peacock would be for ostentatious display as much as for culinary consumption.
Peafowl is generally considered poultry, even though neither its meat nor its eggs are frequently eaten. It is considered poultry due to the possibility that the meat and eggs can be eaten and that the species is often raised for its feathers.
- "Peacock (bird)". Britannica Online Encyclopedia.
- Darwin, Charles. (1871), The Descent of Man and Selection in Relation to Sex John Murray, London.
- Jacobs, M. March 10, 1999. A New Look at Darwinian Sexual Selection. Natural Science. [9/14/2014]; http://naturalscience.com/ns/articles/01-11/ns_mej.html
- Manning, JT. December 19, 2002. Age-advertisement and the evolution of the peacock’s train. Journal of Evolutionary Biology. [9/14/14]; 2(5), 379-384. http://onlinelibrary.wiley.com/doi/10.1046/j.1420-9101.1989.2050379.x/pdf.
- Manning, JT. December 19, 2002. Age-advertisement and the evolution of the peacock’s train. Journal of Evolutionary Biology. [9/14/14]; 2(5), 379-384. http://onlinelibrary.wiley.com/doi/10.1046/j.1420-9101.1989.2050379.x/pdf.
- Caldwell, Roy, and Jennifer Collins. "When Sexual Selection Runs Away (1 of 2)." Evolution 101: Runaway Selection. N.p., n.d. Web. 24 Nov. 2014. <http://evolution.berkeley.edu/evosite/evo101/IIIE3aRunawayselec.shtml>.
- Zuk, Marlene. (2002). Sexual Selections: What we can and can't learn about sex from animals. University of California Press; Berkeley, CA. ISBN 0520240758
- Davies N, Krebs J, and West S. (2012). An Introduction to Behavioral Ecology, 4th Ed. Wiley-Blackwell; Oxford.
- Male Peacock's Feather Fails to Impress Females: Study. Thaindian News. 27 March 2008.
- Petrie, M.; Halliday, T.; Sanders, C. (1991). "Peahens prefer peacocks with elaborate trains". Animal Behavior 41 (2): 323–331. doi:10.1016/S0003-3472(05)80484-1.
- Petrie, M. (1992). "Peacocks with low mating success are more likely to suffer predation". Animal Behaviour 44: 585–586. doi:10.1016/0003-3472(92)90072-H.
- Zahavi, Amotz (1975). "Mate selection—A selection for a handicap". Journal of Theoretical Biology 53 (1): 205–214. doi:10.1016/0022-5193(75)90111-3. PMID 1195756.
- Takahashi, Mariko; Arita, Hiroyuki; Hiraiwa-Hasegawa, Mariko; Hasegawa, Toshikazu (2008). "Peahens do not prefer peacocks with more elaborate trains". Animal Behaviour 75 (4): 1209–1219. doi:10.1016/j.anbehav.2007.10.004.
- "Do peahens not prefer peacocks with more elaborate trains?". Anim. Behav. 76: e5–e9. 2008. doi:10.1016/j.anbehav.2008.07.021.
- Jacobs, M. (10 March 1999). A New Look at Darwinian Sexual Selection. Natural Science.
- Jordania, Joseph (2011) "Peacock's Tail: Tale of Beauty and Intimidation". pp. 192–196 in Why do People Sing? Music in Human Evolution Logos.
- Dakin, Roslyn; Robert Montgomerie (2013). "Eye for an Eyespot: How Iridescent Plumage Ocelli Influence Peacock Mating Success". Ebscohost. The Original Journal of the ISBE.
- Yorzinski, Jessica L.; Gail L. Patricelli; Jason S. Babcock; John M. Pearson; Michael L. Platt (2 April 2013). "Through Their Eyes: Selective Attention in Peahens During Courtship". The Journal of Experimental Biology.
- Loyau, Adeline; Michel S. Jalme; Gabriele Sorci (2005). "Intra- and Intersexual Selection for Multiple Traits in the Peacock (Pavo Cristatus)". Ebscohost (Blackwell Verlag).
- Yorzinski, Jessica L.; K. R. Annop (5 November 2012). "Peacock Copulation Calls Attract Distant Females". Ebscohost (Brill).
- "Birds, symbolic". Peter and Linda Murray, Oxford Dictionary of Christian Art (2004).
- Ayyar, SRS. "Muruga – The Ever-Merciful Lord". Murugan Bhakti: The Skanda Kumāra site. Retrieved 31 March 2014.
- Seznec, Jean (1953) The Survival of the Pagan Gods: Mythological Tradition in Renaissance Humanism and Art
- Ovid I, 625. The peacock is an Eastern bird, unknown to Greeks before the time of Alexander.
- Brown, Les (1977). The New York Times Encyclopedia of Television. Times Books. p. 328. ISBN 0-8129-0721-3.
- "Fowl Recipes". Medieval-Recipes.com. 2010. Retrieved 30 March 2012.
|Wikiquote has quotations related to: Peafowl|
|Look up peafowl in Wiktionary, the free dictionary.|
|Wikimedia Commons has media related to Pavo cristatus.|
- Peafowl Varieties Database
- Etymology of the word Peacock
- Peafowl videos, photos & sounds on the Internet Bird Collection.
- Behavioural Ecologists Elucidated How Peahens Choose Their Mates, And Why, an article at Science Daily.