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Monday, July 25, 2011

Parrot-Psittacines



Beauty Of AnimalParrot-Psittacines | 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.

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, have diminished wild populations, with parrots being subjected to more exploitation than any other group of birds. Recent conservation measures 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 1002 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–Tertiary extinction event, 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).

Europe is the origin of the first presumed parrot fossils. The first is a wingbone of Mopsitta tanta, uncovered in Denmark and dated to 54 mya (million years ago). The climate at this time was tropical, consistent with the Paleocene-Eocene Thermal Maximum.
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