2. Feathers: Birds have feathers, which are lightweight, branched structures that cover their entire body. Feathers help birds fly by reducing drag, providing lift, and insulating the bird's body.
3. Hollow bones: Most bird bones are hollow, which reduces their weight and allows them to fly more efficiently.
4. Strong flight muscles: Birds have powerful flight muscles that are attached to their wings. These muscles provide the power needed for birds to flap their wings and fly.