List the flight devices that are clearly visible in the external structure of birds.

Birds are animals that are ideally suited to flight. This is clearly seen in their external structure:
– streamlined body shape – reduces air resistance;
– beak – increases streamlining by cutting the air;
– long narrow nostrils located on the sides of the beak – make breathing possible in flight;
– the front limbs have changed into wings;
– feathers: a) contour – provide flight, b) down – retain heat;
– in the leg – a special section – the tarsus, which increases the shock absorption when landing.