Human Beings are a species but there are many races of humans. The same is true for birds. When you go birding you may notice that some birds, such as the Yellow-rumped Warbler, look different in the East than the same species does in the West. Different races of the same species often are separated geographically. We are interested in a class of animals with backbones known as birds.
Birds have feathers and lay eggs.
All birds have wings. However, not all birds can fly. The Ostrich is too heavy to fly. Penguins use their wings to swim, instead of to fly. After many centuries, their ancestors had evolved to the point where they were unable to fly.