9 Tail Backbone Secondary flight feathers Primary flight feathers Hind toe Ankle Tibia Radius Femur Alula Claw Cranium Long fins Neck vertebrae Eye socket Humerus Design for flight Flight makes enormous demands on a bird’s body. Once airborne, a bird like a heron may save energy by gliding, but it requires all the power it can produce for its initial take-off. As well as having a lightweight skeleton, birds have a high metabolic rate – the speed at which they turn food into energy, which helps them to fly. Long neck Birds have more bones in the neck than most vertebrate animals. A bird such as a heron has a flexible neck, which it uses to catch food and to preen all parts of its body with its beak. Thumb Finger Animals that fly Birds and bats are the only vertebrate animals capable of true powered flight. Some other animals are able to glide on unpowered “wings”. Flying fish The gurnard can glide above the water on extended fins. Flying squirrels Some squirrels use loose flaps of skin to glide through the air. Flying frogs The webbing between the frog’s feet act like miniature parachutes to enable it to glide between trees.