Birds are the most specialized group of vertebrates on the planet. 
They are unusually heterogenous for a class level group of organisms, meaning that they are all very different from each other while still being in the same class. Birds are bipedal, meaning they walk on two legs, and they are also homeothermic. Birds are characterized by their feathers, hollow bones, four-chambered hearts, and specially designed lungs. They have a streamlined body and centralized weight specifically designed for flying. They have extremely strong flight muscles and tendons. Birds range from being herbivorous(seed and plant eating birds, such as sparrows), to omnivorous(birds that eat both plants and animals, such as turkeys), to carnivorous(meat eating birds, such as eagles). Birds also have very sharp vision, which they use to hunt for their food. Birds also have feathers, which they use for flying, attraction, and to keep warm.
