Why are birds called 'feathered bipeds' ? How are they adapted for flying ?

Explanation

The body of birds is covered with feathers and they rest on the hindlimbs alone. This is the reason why they are called feathered bipeds.
Boat shaped, streamlined body, forelimbs modified into wings, delicate and light endoskeleton, excretory matter chiefly in the form of uric acid, presence of crop and gizzard.