up, the skeleton for the wing was constructed. In total, 15 bones were
initially set up to house groups of 1 to3 feathers at each level (outer,
middle section and front). In this way, a single bone could be responsible
for up to 8 or so individual planes at different levels of the wing but
all in the same lateral group. This was the basis for achieving proper
fanning of the feathers, both outward and inward when the elbow and shoulder
pull the arm in close to the body or extend it straight.
These have their own fanning properties during flight and spread out independently of the rest of the wing. They also follow the characteristic wrist action of a bird as it scoops the air backward at the end of the down stroke so they needed to be bound immediately below a discreet joint which would be the wrist (green circle below)
Secondly, the rest of the feathers (from just right of the middle of the wing to the left edge near the body) needed to be separated themselves to accomodate the elbow joint and make way for successful collapsing for the whole wing (circled blue)
Below shows us the final skeltal preparation for the whole wing to allow for successful fanning and collapsing with discreet feathers sliding over one another without intersection. Also with a 'semi-root' sholder joint for initial basic wing cycle animation and finally, an 'arm' section to allow placement of a feathery tube as the leading edge with extending fingers and claws.
The above image also shows the 'wing-attached' (leftmost) layer of feathers which are not bound so that they fan. Rather, they are bound straight to the joint above the shoulder so that they also do not move with the wing flap. You will see later how a lattice ensures that they form a smooth transition between body and wing during flight animation.