To Hover, Hummingbirds Use Precision Feather Control
Editor's Note: If you're in the Seattle area and missed our announcement yesterday of a pretty irresistible bonus for those who attend the FREE July 17 theatrical premiere of Flight, at the Museum of Flight, go back and look at that now.
A video clip from BBC News shows a hummingbird controlling the orientation of its wing feathers as it hovers. The accompanying text explains:
Hummingbirds' main flight feathers slide as they flap, changing the shape and size of the wing and precisely controlling the lift their wings produce. (Emphasis added.)
In the Illustra documentary Flight, Dr. Thomas Emell of the University of Florida asks us to consider the speed of the synapses firing during the birds' wingbeats (more than 80 times a second) and heartbeats (1,250 times a minute). Now, we see that each wingbeat, taking place in less than 10 milliseconds, involves even more control: tuning the wing shape at each position to optimize lift.
Masateru Maeda, a PhD student at Chiba University in Japan, captured the footage.
The ultimate aim of his measurements of the movements of the wings is to copy their function in the design of flying robots.
If something works, it's "not happening by accident," Discovery Institute Fellow Paul Nelson reminds us in the Illustra film. He describes how the unique shape of the shoulder bone allows the wing to invert on the reverse stroke, creating lift on both strokes. Now, Maeda has found that hovering also requires the hummingbirds to be able to sense their wings' shapes and respond accordingly.
Mr Maeda said that the birds must have a very acute sense of their wings' shape in order to remain so still in the air.
"If the wing shape isn't optimised," he explained, "it will fail to produce lift and the bird will start to sink.
"So it must be able to sense this and correct the shape of its wings."
What this implies is that the wing shape (involving control of the flight feathers' ability to slide as they flap), is under instantaneous control of the hummingbirds' central nervous system. The speed of signals from brain to flight muscles now becomes even more astonishing.
In the documentary, viewers see a robotic hummingbird called the Nano Air Vehicle able to hover in mid-air. Its wings, however, perform simple back-and-forth movements while its stiff body floats upright in a fixed position. It has no internal guidance system, no heart or brain, and no fine control of wing shape. Without the human operator and his joystick, it would crash into the nearest wall. No wonder Nelson says that, despite its being a "sensational piece of engineering," it is still "light years behind the bird that inspired its creation."
Real hummingbirds accomplish all this from the energy of nectar. They are also able to hatch into adults from tiny eggs that undergo the dramatic development illustrated in the film. Birds are "integrated wholes," Biologic Institute senior research scientist Ann Gauger remarks, "not just the sum of their parts. They are alive and responsive," she continues, challenging the view that unguided natural processes could explain their origin.
If Darwinian evolution were a true and complete explanation of how complex life got to be as it is, we would expect living systems to get simpler the closer we look. Hummingbirds show that the opposite is the case.