Question

birds are lightweight as they ​

Answer 1

Answer:

The skeletons of birds are universally described as lightweight as a result of selection for minimizing the energy required for flight. ... I found that, on average, these bones are densest in birds, followed closely by bats. As bone density increases, so do bone stiffness and strength

Answer 2

Answer:

The skeletons of birds are universally described as lightweight as a result of selection for minimizing the energy required for flight. From a functional perspective, the weight (mass) of an animal relative to its lift-generating surfaces is a key determinant of the metabolic cost of flight.