Class Aves comprises about 10,000 species, dwelling in a large variety of habitats and found in most geographical areas of the planet. Their body is covered with feathers, and their front limbs have evolved to become wings, which enable most of the species to fly. Birds have many other adaptations that contribute to the ability to fly, such as hollow bones and a unique respiratory system that includes air sacs. Birds breed by laying hard-shelled eggs, and in most species the parents tend to their young.
The Zoological Research Garden hosts about 100 species of birds, many of which can be found on the main grass area in the center of the Garden and are free to come and go as they please. Among the birds in the Garden are passerine birds, birds of prey, owls, water birds, and invasive birds.