Birds (class Aves) are winged, bipedal, endothermic (warm-blooded), vertebrate animals that lay eggs.
There are around 10,000 living species, making them the most numerous tetrapod vertebrates.
They inhabit ecosystems across the globe, from the Arctic to the Antarctic.
Birds range in size from the 5 cm (2 in) Bee Hummingbird to the 2.7 m (8 ft 10 in) Ostrich.
The fossil record indicates that birds evolved from theropod dinosaurs during the Jurassic period,
around 150–200 Ma (million years ago), and the earliest known bird is the Late Jurassic Archaeopteryx,c 155–150 Ma.
Most paleontologists regard birds as the only clade of dinosaurs that survived the Cretaceous–Tertiary extinction event approximately 65.5 Ma.

Las aves son animales vertebrados, de sangre caliente, que caminan, saltan o se mantienen solo sobre las extremidades posteriores, mientras que las extremidades anteriores están modificadas como alas que, al igual que muchas otras características anatómicas únicas, son adaptaciones para volar, aunque no todas vuelan. Tienen el cuerpo recubierto de plumas y, las aves actuales, un pico córneo sin dientes. Para reproducirse ponen huevos, que incuban hasta su eclosión.
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