Bird anatomy consists of several key features that enable flight and survival. Birds have a lightweight skeleton with hollow bones, which reduces their overall weight. Their bodies are covered in feathers, which provide insulation, waterproofing, and the ability to fly. The beak, or bill, varies in shape and size depending on the bird's diet, while their strong muscles support wing movement. The respiratory system of birds is highly efficient, featuring air sacs that allow for continuous airflow through the lungs. Birds also possess a unique digestive system, including a gizzard that grinds food, aiding in digestion. Their keen eyesight and acute hearing help them navigate and find food in their environments.