A nimble correction to the hollow-bones myth, with bats, penguins, and buoyancy neatly rearranged.
The familiar line that birds have hollow bones gets usefully tightened as bats, ostriches, emus, and penguins complicate the shorthand. The hosts move from pneumaticized bones to bats' mammalian skeletons and penguins' marrow-filled bones, then connect that density to buoyancy…






