Leonardo explains that a bird should fly above the clouds to prevent its wings from getting wet and to avoid the circular air patterns that come from mountainous terrain. If a bird flies above the clouds and somehow gets turned over, then it should have plenty of time to turn itself back over by either "[falling] immediately with the wingtip downwind, or lowering the opposite wing to below halfway". He also comments on the rib structure of a bird and theorizes which ribs are the most useful. He ends folio 6 by stating he needs to do more practical tests on the ribs of birds.