Birds
Birds are a group of warm-blooded vertebrates, characterized by feathers, toothless beaked jaws, the laying of hard-shelled eggs, and a strong yet lightweight skeleton. Birds live worldwide and range in size from 2 inches (bee hummingbird) to 9 feet (ostrich). There are about 10,000 living species of birds. Human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them.
Click any of the thumbnails below to see more images of birds from that category.
