Characteristic of Bird

Bird are warm blooded (endothermic), vertebrate that has feathers and a four-chambered heart. Bird also lay eggs in the nest and incubated by the parents. Modern birds are characterized by a beak with no teeth,the laying of hard-shelled eggs, feathers. Most birds can fly, with some exceptions including ratites, penguins. Birds also have unique digestive and respiratory system, the air scas connects to the lung, the air scas enable birds can obtain more oxygen.Many birds have an crop for storing food inside the body after swallowing the food(because the bird don't have the teeth, so they cannot chew their food). The crop connected to the stomach. The stomach have two parts. First part break the food down, then the food moves to the gizzard, the gizzard squeezes and grinds the remnant food . The gizzard just like our teeth. The circulatory system : birds have four-chambered heart, two atria and two ventricles. The right ventricle pumps to the lungs, while left ventricle pumps blood to the rest of the body.