Most of their bones are hollow, and act like airpockets. Birds are mostly feathers, and feathers do not weigh much. Birds have wings to help them fly. They have strong muscles to be able to fly for long periods of time. Not all birds fly in the same way.
Birds soar,glide, flap their wings quickly, hover,and dive.
They are able to ride the updrafts of air. The wings of a pigeon, ducks, and other water fowl are called general-purpose wings. The hummingbirds wings beat so quickly that they look like a blur. It is even able to fly backwards. The loon is not a good flier.