I found a dead Finch on the ground today; pick it up and studied it. I pulled open the wings and saw how the flight feathers were shaped with the quill off to one side. The tail feathers were similar.The down feathers seem to create a volume that defines where the body feathers rest. It makes sense to me now, how the shape is maintained.I placed the bird in the woods away from the house, sad but grateful.

Sorry about the picture quality. I have applied most of the body feathers. Some of the wing feathers are on.
Frank