Birds have undergone many structural adaptations to suit their aerial life. Some of these adaptations are as follows :(i) Streamlined body for rapid and smooth movement.(ii) Covering of feathers for insulation.(iii) Forelimbs modified into wings and hind limbs used for walking, perching, and swimming.(iv) The presence of pneumatic bones to reduce weight.(v) The presence of additional air sacs to supplement respiration.