I was taking a photograph of sparrows and goldfinches at my feeder during a rare lower Alabama snowstorm a few years ago. By sheer happenstance a female cardinal flew through the frame and demonstrated that birds are not always flapping while flying. She is out of focus but it is clearly obvious that her wings are fully folded in. It is probably an energy-saving technique. I have seen small birds fly through chain link fences without stopping. I would guess they use the same ballistic technique.
