|Human arm top, bird wing bottom|
Humerus - Innermost bone, between body and elbow.
Ulna/Radius - middle or forearm bones, between elbow and wrist. The secondary feathers are attached to the ulna.
Hand - Outermost bone, some metacarpals are missing, some are fused together. One of the digits is the thumb or alula, a small group of three or four feathers are attached to the bone. The ten primary flight feathers (nine in some perching birds) are attached to the hand.