According to Dr Sapir, the most important finding of the study was that flying backwards uses a similar amount of energy to flying forwards, both of which were more efficient than hovering.
[Hummingbirds swivel their wrists in a figure 8 pattern, while other birds swivel their shoulders.]
He continued, "During backward flight, the bird's body is held in [a] much
more upright posture. We were expecting the body will experience a much higher
drag and that the bird will need to invest much more work to overcome this
Further investigation using life-sized models determined that drag during
backward flight is only slightly higher than when the bird is flying
"[This is] probably because drag forces are relatively negligible at flight
in relatively slow airspeeds, as characterising backward flight," he said.
High speed hummers beat jets
Bird flight based on single angle flapping