The term peafowl refers to Gallinaceous Birds classified within the genera Rheinardia, Argusianus, Afropavo,and Pavo. Formerly classified as members of the Phasianidae, it is now established that the Phasianidae do not share the same ancestry. Peafowl and their allies are a very ancient isolated group with no near allies.
Peafowl are large birds with long necks and legs, heavy squarish wings and elongated tails. Adult males of most genera can be distinguished from females by their extremely elongated and highly specialized dorsal plumage. Adult males of the two species of Great Argus exhibit highly specialized wing coverts which give them the largest wing surface area of any living bird. The Great Argus male's wing is shaped rather like a moth's and is patterned very much like a python. Some native cultures in Burma and Thailand refer to the Great Argus as "Python Moth Bird" for this reason. The Great Argus male also exhibits extremely elongated tail feathers (retrice plumes) which are twisted at their ends. Each of the two central retrices resemble snake heads in silhouette, a feature best appreciated in shadows cast by the tail when the birds stand in stationary alert posture. When in this posture the tail is held high in a carriage not unlike a bantam rooster. The elongated retrices jut out and the bird raises them as if to broadcast the presence of the two feathered "heads". The female Great Argus is essenitally similar to the male but smaller, brighter in colour and without the greatly elongated wing and tail plumage. The female Great Argus also exhibits much more feathering along the back of the head and neck.
Males of the two species of Crested Argus lack the greatly elongated wing coverts of their cousins the Great Argus but their wings are very large for their body size. Adult male Crested Argus also exhibit enormous tail feathers just as long as the Great Argus but at least twice as wide. The entire tail is elongated, not only the central retrices. Like the Great Argus, the Crested Argus Male is most striking in prolonged flight. Crested Argus fly in pairs and also with their juvenile offspring in the manner of typical Peafowl. Great Argus may also fly in pairs. Great Argus exhibit complex flight displays in which the female participates. Congo and Green Peafowls also exhibit flight displays. The Indian Peafowl's flight displays are evidentially reduced to stereotypical jumps and glides.
Peafowl differ from most other gallinaceous birds in their habit of gathering on emergent trees well above the canopy in primeval forest habitats or on single tall trees towering over tropical grasslands. Their incubation periods are comparatively long - from 28-34 days. Like other large bodied primitive Gallinates, such as the distantly related Megapodes and Cracides, all members of the Peafowl family are capable of making sustained flights of several yards within a few days of hatching. They are born with perfectly formed flight feathers. Junglefowl, Francolins, Partridges, Quail, Pheasants and Grouses develop their wing feathers later than peafowl and are not capable of sustained flight until they are at least one week old. Monals and Tragopans are born with developed flight feathers and they too can sustain flight before they are one week old. Peafowl have unique musculature of the leg, tail and breast that distinguish them from other Gallinates. Their hind toes are longer than other Old World Gallinates (except for members of the Genus Polyplectron which are believed to be distantly related).
While Peafowl are born with developed flight feathers they require a great deal of parental care, which is provided by both parents of all species except captive populations of the Indian Peafowl. Their markedly delayed maturity is another unique characteristic of peafowl that is in keeping with the offspring's prolonged relationships with their parents.
Adult males provided Charles Darwin with the very embodiment of his Theory of Sexual Selection. This theory was based on the behaviors of captive-bred Indian Peafowl living in England. Darwin believed that the adult male displayed his beautiful train feathers to attract a mate and that he played no role in nest defense or chick rearing. In fact, of all the Galliform birds, the adult male Peafowl may have the most - rather than the least - invested in nest defense.
The Adult Male Peafowl defends the nest site against reptiles and other predators. Monitor Lizards, Cobras, Pythons and opportunistic predators like civets and monkeys all pose the worst threats to the Peahen, especially when she is incubating the clutch on or near the ground. The males defend the nest site and the foraging territories of their mates. The juvenile offspring of previous seasons closely resemble their mothers and often participate in helping the parents rear the next clutch. For this reason early Western naturalists assumed that the males kept "harems" of females. The territory-holding male actually provides more care of the young than the female, as he watches over the youngsters until they are fully adult while their mother is done with them in their first dry season (winter). The helper system is more pronounced in some genera and species than others.
The two species are:
The Indian Peafowl is monotypic, while the Green Peafowl has 3 subspecies, P. muticus spicifer, P. m. imperator and the nominate P. m. muticus. The two species are largely allopatric but will hybridize in captivity.
While the form of Green Peafowl in Yunnan is not separated taxonomically, it differs in a few aspects from other forms, particularly in its forest-dwelling habits, an "odd, monal-like bill," a curiously long hind toe and longer, more slender wings (K. B. Woods in litt. 2000) . Some have suggested this is a new subspecies.
Some pheasant breeders have suggested that the Green Peafowl may have more subspecies.
Peafowl have sometimes been included in a distinct family from Pheasants .
The male (peacock) Indian Peafowl has iridescent blue-green or green coloured plumage. The so-called "tail" of the peacock, also termed the "train," is not the tail quill feathers but highly elongated upper tail coverts. The train feathers have a series of eyes that are best seen when the tail is fanned. Both species have a crest atop the head.
The female (peahen) Indian Peafowl has a mixture of dull green, brown, and grey in her plumage. She lacks the long upper tail coverts of the male but has a crest. The female can also display her plumage to ward off female competition or danger to her young.
The Green Peafowl is very different in appearance to the Indian Peafowl. The male has green and gold plumage and has an erect crest. The wings are black with a sheen of blue.
Unlike the Indian Peafowl, the Green Peahen is very similar to the male, only having shorter upper tail coverts and slightly less iridescent in some regions. Like other peafowl, it is very difficult to distinguish a juvenile male from an adult female. Moreover, the sexes of the various Green Peafowl species are almost impossible to tell apart in the field during the months when the male has no train.
Many of the brilliant colours of the peacock plumage are due to an optical interference phenomenon (Bragg reflection) based on (nearly) periodic nanostructures found in the barbules (fiber-like components) of the feathers.
Different colours correspond to different length scales of the periodic structures. For brown feathers, a mixture of red and blue is required: one colour is created by the periodic structure, and the other is a created by a Fabry-Perot interference peak from reflections off the outermost and innermost boundaries of the periodic structure.
Such interference-based structural colour is especially important in producing the peacock's iridescent hues (which shimmer and change with viewing angle), since interference effects depend upon the angle of light, unlike chemical pigments.
The peafowl are forest birds that nest on the ground. The Pavo peafowl are terrestrial feeders but roost in trees.
Both species of Peafowl are believed to be polygamous. However, it has been suggested that "females" entering a male Green Peafowl's territory are really his own juvenile or subadult young (K. B. Woods in litt. 2000) and that Green Peafowl are really monogamous in the wild. The male peacock flares out its feathers when it is trying to get the females attention. Those who subscribe to this notion cite the similarities between the sexes.
During mating season they will often emit a very loud high pitched cry.
In common with other members of the Galliformes, males of most species and females of all but two species, possess powerful, wickedly sharp, metatarsal spurs or "kicking thorns" used primarily to protect themselves against predators and to a lesser extent during intraspecific fights.
Because of human encroachment into their natural territories, peafowl and humans have come into increasing contact. Because of their natural beauty some are reluctant to classify the birds as pests but their presence can be disturbing.