Assertion: bird's skeleton | /r/HasProperty | light
Facets:
Source sentences:
text: Flying birds have light skeletons with many hollow bones.
text: Birds have various adaptations for flight, including a lightweight skeleton, two large flight muscles, the pectoralis (which accounts for 15% of the total mass of the bird) and the supracoracoideus, as well as a modified forelimb (wing) that serves as an aerofoil.