Genghis,
A bit outside Quinten's subject and field, but it's worth looking at a birds feathers on its "hands", the alulae and primaries.
Somehow, I've never seen any aircraft design use small outboard leading edge slats for roll control similar to the alulae.
Weirdly, I can imagine immediately spreading my arms to soar and then "twitch" my thumbs (the alulae) to maintain steady flight, and spread one hand downward to sharply turn into a bank...
CJ