[wendy1946]

The light bone structure is the least of the thing you'd need before you became a flying bird. The hardest item would likely be flight feathers. Aside from that, you'd need mutations which selectively mutated the pre-existing insulation/down feathers into flight feathers on wings, fail feathers on tails, and left the down feathers alone on the rest of the proto-bird.

Which side is it which is talking about miracles??

[Stultis]

The hardest item would likely be flight feathers. Aside from that, you'd need mutations which selectively mutated the pre-existing insulation/down feathers into flight feathers on wings, fail feathers on tails, and left the down feathers alone on the rest of the proto-bird.

The latest research suggests that all you need to form all the feather types are a couple additions to a basic activator-inhibitor system, which already explains the formation of downy feathers. See (full text):

Molecular evidence for an activator-inhibitor mechanism in development of embryonic feather branching. PNAS August 16, 2005 vol. 102 no. 33 11734-11739

Since we have the identity of the basic activator and inhibitor, finding the additional activator and another local inhibitor -- if this theory is accurate -- shouldn't take too long. Then you'll have to move the goal posts again. (Or, more likely, just ignore it.)