See, the african swallows use the cutout in their tails to create a space time vortex that stirs up anti-gravitons thus creating more lift as they fly. Its a process that we have been unable to duplicate in aeronautics but have succeeded in snowboarding. Its a bit of a complicated matter regarding specific densities and subatomic spin orientationing. Dont get all this confused with the european swallows though as they employee a completely different process primary using the quantum entanglement theories regarding left quarks.
But can they carry a coconut?