Parrots, also known as psittacines (pronounced /ˈsɪtəsaɪnz/), are birds of the roughly 372 species in 86 genera that make up the order Psittaciformes,found in most warm and tropical regions. The order is subdivded in three families: the Psittacidae (true parrots), the Cacatuidae (cockatoos) and the Nestoridae.[5] Parrots have a pan-tropical distribution with several species inhabiting the temperate 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. Most parrots are predominantly green, with other bright colors, and some species are multi-colored. Cockatoo species range from mostly white to mostly black, and have a mobile crest of feathers on the top of their heads. Most parrots are monomorphic or minimally sexually dimorphic. Extant species range in size from the Buff-faced Pygmy-parrot, at under 10 g (0.35 oz.) in weight and 8 cm (3.2 inches) in length, to the Hyacinth Macaw, at 1.0 meter (3.3 feet) in length, and the Kakapo, at 4.0 kg (8.8 lbs) in weight. They are 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, and a few species also eat insects and small animals, and the lories and lorikeets are specialised to feed on nectar from flowers, and soft fruits. Almost all parrots nest in tree holes (or nestboxes in captivity), and lay white eggs from which emerge altricial (helpless) young.
Parrots, along with crows, jays and magpies, are some of the most intelligent birds, and the ability of some parrot species to imitate human voices enhances their popularity as pets. Trapping of wild parrots for the pet trade, as well as other hunting, habitat loss and competition from invasive species, have diminished wild populations, and parrots have been subjected to more exploitation than any other group of birds.[6] Recent conservation measures to conserve the habitats of some of the high-profile charismatic parrot species has also protected many of the less charismatic species living in the ecosystem.
The word snail is a common name that can be used for almost all members of the molluscan class Gastropoda that have coiled shells in the adult stage. (Snails lacking a shell or having only a very small one are usually called slugs. Snails that have a broadly conical shell that is not coiled, or appears not to be coiled, are often known as limpets.) When the word snail is used in a general sense, it includes sea snails, land snails and freshwater snails.
The class of Gastropoda (the snails and slugs) is second only to the insects in terms of total number of species. Snails are extraordinarily diverse in habitat, form, behavior, and anatomy, and therefore what is true of one snail species may not at all be true of another.
Snails can be found in a wide range of different and alike environments from ditches to deserts to the abyssal depths of the sea. The great majority of snail species are marine. Many others are terrestrial, and numerous kinds can be found in fresh water, and even brackish water. Many snails are herbivorous, though a few land species and many marine species are omnivores or predatory carnivores.
Although the average person might perhaps be more familiar with terrestrial snails, land snails are in the minority. Marine snails have much greater diversity, and a greater biomass. Snails which respire using a lung belong to the group Pulmonata, while those with gills form a paraphyletic group, in other words, snails with gills are divided into a number of taxonomic groups that are not very closely related.
Snails with lungs and with gills have diversified widely enough over geological time that a few species with gills can be found on land, numerous species with a lung can be found in freshwater, and a few species with a lung can be found in the sea.
Although the word snail is often used for all shelled gastropods, the word "snail" can also be used in a much more limited sense, to mean various larger species of air-breathing (pulmonate) land snails. The majority of this article is about air-breathing land snails.
