Bird Pet Shops 108

Birds (Aves), also known as avian dinosaurs, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton.

Birds live worldwide and range in size from the 5 cm (2 in) bee hummingbird to the 2.75 m (9 ft) ostrich. They rank as the class of tetrapods with the most living species, at approximately ten thousand, with more than half of these being passerines, sometimes known as perching birds or, less accurately, as songbirds.

Birds have wings which are more or less developed depending on the species; the only known groups without wings are the extinct moas and elephant birds. Wings, which evolved from forelimbs, gave birds the ability to fly, although further speciation has led to the loss of flight in flightless birds, including ratites, penguins, and diverse endemic island species of birds.