Cockatiel in Flight
Prior to the first motion pictures, Eadweard Muybridge produced a series of stop-motion photographs of animal movement in 1877, which, when viewed in succession, effectively produce the first “moving pictures”.
Cockatiels are a good example of a bird which uses primarily non-gliding (flapping) flight. During the downstroke (power stroke), the wing moves forward and downward, producing thrust. The upstroke, or recovery stroke, involves the flight feathers separating, to allow the air to flow through them. This, combined with the wing partially folding in towards the body, reduces drag significantly.
Handbuch der Biologie der Wirbeltiere. Dr. M. Hilzheimer, 1913.