Forgive me, but I'm still not sure I understand.
If it's 'non physical', does it interact in any way with the natural world (aka reality)?
If so, why would you consider it 'non physical'?
If it doesn't interact with the natural world, why would you speculate it's existence in the first place? based on what?
Thank you for taking the time to answer, I appreciate it.
RE: The Bio-Physics of Bird Flight