Well watch the dynamics. Lots of flapping and running. Then he just kind of leaps off the ground and climbs pretty dramatically, all with no increase in flapping frequency. Then he gets to the top of the climb, kind of hovers, without flapping. Birds flap like crazy when they do this. The final item, look at the trailing edges of the wing. They kind of flutter in the breeze. The wing never appears loaded like a parawing or hang glider wing.
However, if it works, I want one. Always on the hunt for a new way to kill myself.