Parrots, also known as psittacines, are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes, found in most tropical and subtropical regions. The order is subdivided into three families: the Psittacidae ('true' parrots), the Cacatuidae (cockatoos) and the Strigopidae (New Zealand parrots). Parrots have a generally pantropical distribution with several species inhabiting temperate regions in the Southern Hemisphere as well. The greatest diversity of parrots is found in South America and Australasia. [1]Characteristic features of parrots include a strong, curved bill, an upright stance, strong legs, and clawed zygodactyl feet. Many parrots are vividly coloured, and some are multi-coloured. The plumage of cockatoos ranges from mostly white to mostly black, with a mobile crest of feathers on the tops of their heads. Most parrots exhibit little or no sexual dimorphism. They form the most variably sized bird order in terms of length.
The most important components of most parrots' diets are seeds, nuts, fruit, buds and other plant material. A few species sometimes eat animals and carrion, while the lories and lorikeets are specialised for feeding on floral nectar and soft fruits. Almost all parrots nest in tree hollows (or nest boxes in captivity), and lay white eggs from which hatch altricial (helpless) young.
Parrots, along with ravens, crows, jays and magpies, are among the most intelligent birds, and the ability of some species to imitate human voices enhances their popularity as pets. Trapping wild parrots for the pet trade, as well as hunting, habitat loss and competition from invasive species, has diminished wild populations, with parrots being subjected to more exploitation than any other group of birds. Measures taken to conserve the habitats of some high-profile charismatic species have also protected many of the less charismatic species living in the same ecosystems.
Researchers are unsure about the origins of parrots. Psittaciforme diversity in South America and Australasia suggests that the order may have evolved in Gondwanaland, centred in Australasia. The scarcity of parrots in the fossil record, however, presents difficulties in proving so.A single 15 mm fragment from a large lower bill (UCMP 143274), found in deposits from the Lance Creek Formation in Niobrara County, Wyoming, had been thought to be the oldest parrot fossil and is presumed to have originated from the Late Cretaceous period, which makes it about 70 million years old. There have been studies, though, that establishes that this fossil is almost certainly not from a bird, but from a caenagnathid theropod or a non-avian dinosaur with a birdlike beak.
It is now generally assumed that the Psittaciformes, or their common ancestors with a number of related bird orders, were present somewhere in the world around the Cretaceous–Paleogene extinction event (K-Pg extinction), some 65 mya (million years ago). If so, they probably had not evolved their morphological autapomorphies yet, but were generalised arboreal birds, roughly similar (though not necessarily closely related) to today's potoos or frogmouths (see also Palaeopsittacus below). Though these birds (Cypselomorphae) are a phylogenetically challenging group, they seem at least closer to the parrot ancestors than for example the modern aquatic birds (Aequornithes). The present-day combined evidence is widely in support of the hypothesis of Psittaciformes being "near passerines"; i.e. they almost certainly belong to the radiation of mostly land-living birds that emerged in close procimity to the K-Pg extinction. They have been variously allied to to groups such as falcons, songbirds, trogons, woodpeckers, as well as "Coraciiformes", hawks and owls, and the puzzling mousebirds. This seems to be by and large correct. Other proposed relationships, such as to pigeons, are considered more spurious today.
Europe is the origin of the first presumed parrot fossils, which date from about 50 million years ago (mya). The climate there and then was tropical, consistent with the Paleocene-Eocene Thermal Maximum. Initially, a neoavian named Mopsitta tanta, uncovered in Denmark's Early Eocene Fur Formation and dated to 54 mya (million years ago), was assigned to the Psittaciformes; it was described from a single humerus. However, the rather nondescript bone is not unequivocally psittaciform, and more recently it was pointed out that it may rather belong to a newly-discovered ibis of the genus genus Rhynchaeites, whose fossil legs were found in the same deposits.The feathers of a Yellow-headed Amazon. The blue component of the green colouration is due to light scattering while the yellow is due to pigment.
Fossils assignable to Psittaciformes (though not yet the present-day parrots) date from slightly later in the Eocene, starting around 50 mya. Several fairly complete skeletons of parrot-like birds have been found in England and Germany. Some uncertainty remains, but on the whole it seems more likely that these are not direct ancestors of the modern parrots, but related lineages which evolved in the Northern Hemisphere and have since died out. These are probably not "missing links" between ancestral and modern parrots, but rather psittaciform lineages that evolved parallel to true parrots and cockatoos and had their own peculiar autapomorphies:
