The lion kingdom formerly got really high efficiency from powered, controlled monocopters.  They approached fixed wing efficiency.  Their efficiency can be much higher than helicopters & quad copters because less mass is wasted on a slowly moving inner wing.

An idea popped in of an unpowered monocopter glider.  The fundamental problem is achieving the glide ratio of a fixed wing glider while flying in a tight circle.  It could be launched into the wind & flown to thermals.  

Efficient monocopters require a very long wing with slow RPM.  The wing would have to be a folding structure & maybe even a novel parachute.  Then there's the problem of motivating the wing to spin without a motor.  Plants manage to do it by falling, but falling is really just flying through an updraft.

Monocopters are susceptible to not knowing their orientation when banked steeply.  The kind of wind required to ascend would require some steep banking.  Lions have long fought this problem.  It basically needs another heading reference to back up magnetic north.  Some kind of directional radio might be the only way.