Characteristic of Birds

Classification
Kingdom: Animalia
Phylum: Chordata
Subphylum: Vertebrata
(unranked) Archosauria
Class: Aves

Birds (class Aves, and clade Avialae) are bipedal, warm-blooded(endotherm), vertebrate animals that lay eggs. Also, birds are the only living branch of dinosaurs. There are around 10,000 living species, making them the most numerous tetrapod vertebrates

Characteristic of Birds

Modern birds are characterised by feathers(contour and down feathers), a beak with no teeth, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton. All birds have forelimbs modified as wings and most can fly, with some exceptions including ratites, penguins, and a number of diverse endemic island species. Birds also have unique digestive(crop,gizzard) and respiratory systems(air sacs) that are highly adapted for flight. Some birds, especially corvids and parrots, are among the most intelligent animal species; a number of bird species have been observed manufacturing and using tools, and many social species exhibit cultural transmission of knowledge across generations.