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 and to counter the resistance offered by the air current.
(ii) Covering of feathers for insulation.
(iii) Forelimbs modified into wings and hind limbs used for walking, perching, and swimming.
(iv) Presence of pneumatic bones to reduce weight.
(v) Presence of additional air sacs to supplement respiration.
(vi) Endoskeleton has hollow long bones to reduce weight that favors flying.
(vii) Uricotelic excretion that helps to reduce storage of water to reduce weight.