Vertebrate Zoology - V. M. Konstantinov 2011

Chordates
Terrestrial or Tetrapod Vertebrates — Amniotes
Class Aves — Subclass Neornithes — Superorder Neognathae — Order Psittaciformes

The order Psittaciformes unites 350 species of medium and small-sized (ranging from 10 g to 1 kg in mass) arboreal forest birds distributed across tropical and subtropical regions, with a few species extending into the temperate zone. The majority are frugivorous or granivorous, while some are carnivorous. Their bill Structure is highly distinctive: the upper jaw is movably articulated with the cranium, and the lower jaw can move not only vertically but also laterally. Many species lead a gregarious lifestyle. Nests are typically built in tree hollows, and less frequently in burrows or rock crevices. The South American monk parakeet (Myiopsitta monachuś) is an exception, as it does not nest in hollows, instead constructing its nests within the lower sections of large communal nests built by other bird species.

The clutch consists of 1 to 8 rounded white eggs. Incubation typically lasts 2 to 4 weeks and is performed solely by the female. Parrots are altricial birds, meaning their hatchlings are born helpless. Both parents feed the nestlings for a period of 5 to 14 weeks.

Brightly colored macaws (Ara) are widespread in South America, crested cockatoos (Cacatuinae) in Australia, and grey parrots (Psittacus) in Africa. New Zealand is home to unique, flightless terrestrial ground parrots (Stringops). One of the New Zealand species, the kea or kaka (Nestor), was originally insectivorous, but following the Introduction of domestic sheep in 1875, it turned to carnivory. Initially, it picked insects from the wool of sheep, but gradually progressed to tearing out flesh and Skin. In some areas, the kea causes significant damage to sheep farming. In West Africa, lovebirds (Agapornis) inflict substantial damage on maize crops.

In Australia, A number of species act as pollinators for flowering plants. One of the most abundant species in the semi-arid steppes and savannas of Australia is the budgerigar (Meloprittacus Undulatus), now widely recognized through its domesticated forms. Their natural plumage is light green with intricate wavy barring on the HEAD, accompanied by a dark blue tail.