Have wings, will fly!

Last Updated 17 January 2011, 10:26 IST

The flying abilities of even the most prosaic bird put airplane maneuvers to shame, and experts at the University of Montana Flight Laboratory know that.

“Birds can do some spectacular things,” says Kenneth Dial, a biologist who in 1988 founded the lab at a field station near the University of Montana. “They can go from 40 miles an hour to zero and land on a branch that’s moving, all in a couple of seconds. It’s inspiring.”

Dial and Bret Tobalske, a biologist and the director of the lab, are trying to bridge the gap in flying abilities between humans and birds. At a laboratory full of wind tunnels, high-speed cameras, lasers, surgical equipment and a device that generates clouds of olive oil, they try to divine the secrets of bird flight.

Dial’s 28 years of studying the functional morphology of birds have led him and others at the lab to insights into ecology, biodiversity, airplane design, aerospace and even paleontology.

In a recent paper, Dial, 57, and graduate student Brandon Jackson, presented an idea about how some dinosaurs used their proto-wings – a possible step in the evolution of flight. They based their paper on the observation of day-old Australian brush turkey chicks.

Dial says some of his key observations have been made watching a bird glide by while he is fly fishing, and then heading back to the lab with a new theory to test. After observing woodpeckers in the lab’s wind tunnel both flying and “bounding” – gliding missilelike with their wings tucked, a behaviour not previously identified in these birds – Tobalske was able to see the same gliding a few hundred yards out of the door, confirming it was not a product of lab conditions.

What happens in flight?

One key to the insights is a small, dark room with two 1,000-frames-per-second cameras, developed by the military to study ballistics, which slow high-speed action in high resolution. Birds in flight are misted with a fog of vaporised olive oil, illuminated by a green strobing laser operating in tandem with the camera.

The system allows researchers to track the movement of misty air around the birds, showing where they are generating lift and drag. It led to the discovery here of a vortex on the leading edge of bird wings. The birds have crystal sensors surgically implanted in their pectorals and elsewhere that measure muscle contractions as they fly.

“Pectorals are the motor for 80 per cent of flight,” said Tobalske. Birds are also put in wind tunnels and photographed at high speed so researchers can see how they perform at 20 miles per hour or more. They are also fitted with tiny masks that measure metabolism. CT scans are used on birds to tease out the hidden physics of flying.

Using technology developed at Brown University, researchers scan birds’ bones and combine that with three-dimensional X-rays taken in flight. Together they create a very real animation of a bird in flight. “It gives you three-dimensional joint movement,” said Ashley Heers, a doctoral student.

“This has been a classic area of research since Leonardo da Vinci,” said Richard Prum, a professor of ornithology and ecology and evolutionary biology at Yale. “Functional morphology is being left behind in a lot of places, but it’s important and they are doing some great stuff.”

Work at the Montana lab has led people to realise how complex flight is and how many different things are happening when a bird flies. “What they have discovered is that bird flight is like Muhammad Ali boxing, with 15 different movements,” he said. Birds clap their wings together at the peak of the upstroke during takeoff – that’s the clatter of a pigeon taking off in the park – and rotate their wings on the way down to get lift. “The wings suck in air, like a fan,” Tobalske said, “and create a jet of air below it travelling at 10 miles per hour.”

The most astounding fliers, in Tobalske’s opinion, are the world’s 9,000 or so species of hummingbirds, which, largely because of their size, have mastered flight like no other bird. The calliope hummingbird weighs only as much as two paper clips, yet it migrates annually between Canada and Mexico. In fact, a major theme in research here is how bird morphology influences its behaviour.

The smaller the bird, for example, the more agile the flying – a swan may need the equivalent of two football fields to take off and get lift, while a hummingbird can rise like a helicopter.

“The smaller the bird, the more viscous the air is,” he said, which is partly why hummingbirds can maneuver so well and for so long. They have evolved with greatly shortened wing bones, and large pectorals that allow them to beat their wings 80 times a second. “A hummingbird can hover like a helicopter for one and a half hours, nonstop,” Tobalske said.

“No other bird can do that.” By comparison, pigeons produce one-tenth the number of strokes. Implanted sensors show that a hummingbird’s wing flaps so fast that the brain is generating the muscle signal for the downbeat of its wing while the wing is still going up.These new, deeper views into winged flight have affected other studies.

Evolved from dinosaurs

Also, the study of birds has led Dial to a novel hypothesis. The one-day-old Australian brush turkey, he says, may behave as theropods once did. Theropods were early winged and feathered dinosaurs that walked mainly on their hind legs and were incapable of flight. Ground-nesting birds like the brush turkey hit the ground running when they are born, a defense from predators.

A day-old brush turkey can run straight up a rock wall or a tree, an ability that diminishes as the bird ages. A key to this skill is flapping its small wings. This is not to try to fly, Dial said, but to serve the same role as a spoiler on a race car: to keep the bird on the ground so it can generate more force with its feet and climb steep walls.

Dial calls it “wing-assisted incline running” and has high-speed videos of ground birds running up walls. When the birds arrive atop a rock, and any threats have passed, they jump to the ground using their wings to slow the descent; that is how Dial believes flight may have begun.

“This form of behaviour – independence, locomotor capacity, parental care and development – could be similar to the life history of the theropod,” he said. As far as birds informing human flight techniques, Dial said he believes the future of human flight will incorporate birds’ remarkable shape-shifting abilities.

“Birds are constantly morphing, and morphing on different levels,” he said.“A bird can look like a bullet, and two milliseconds later looks like a hang glider,” Dial said. “We have a lot more to learn about that. Imagine a 747 blasting off its wings and tail to become a bullet.”

(Published 17 January 2011, 10:26 IST)

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