It's not a rotation issue. It is a geometry issue. Bird wings in Poser cannot flap and fold and have them both be perfect. The individual feathers have to arc and bend aside from the body part itself. Real bird feathers slide under each other as the wing folds, like cards in a deck. Poser can only scruntch them up like an acordian. One way around this is to swap in new wings, but aside from that it it a joint parameter limitation that will always exist.