Answer:
Birds fly by using their wings to create lift. The shape of their wings and the way they move them allows them to generate enough lift to overcome their weight and fly. Birds also use their tail feathers to steer and control their flight.
We know for sure that birds fly with their wings because of the extensive scientific research and observations that have been conducted on birds and their flight. Studies of bird anatomy, physiology, and aerodynamics have all shown that the wings are the primary means by which birds fly. Through these studies, we have learned that birds' wings have specific adaptations, such as feathers, that enable them to generate lift and maneuver in the air. Additionally, high-speed cameras and other technology have allowed us to observe birds in flight, and observe their wing movement, which confirms the role of wings in flight. Also, the observation of flightless birds, such as penguins, support the idea that wings are the main reason for flying.