How are the parts of birds and fish similar in stricter sand function?

Birds and fish share similarities in their anatomical structures that serve similar functions for movement in their respective environments. Both have streamlined bodies that reduce resistance: birds have wings for flight, while fish have fins for swimming. Additionally, both have lightweight skeletal structures that aid in mobility—bones in birds are often hollow, while fish have flexible skeletons. These adaptations reflect their evolutionary paths toward efficient locomotion in air and water.