News from the Flight Deck
Now that Illustra’s latest intelligent-design documentary, Flight: The Genius of Birds, has taken off, let’s take a closer look at some of the science in the film as reflected in recent news items.
Peering Into the Eggshell
For the first time, scientists have used MRI to image a chick growing inside the shell. A report from the Max Planck Institute describes the challenge of keeping the image plane aligned each day, since the chicks make unpredictable movements. Each day of the 21-day incubation period, they carefully set up the egg of a Marans chicken in the same plane, to capture images at 12 frames per second. Of special interest to the team was the hatching process, a herculean effort by the chick to escape its initial home:
The hatch itself is subject to biological variation. After 18 days, the chick is fully developed, but only after 21 days is it ready to leave the eggshell. The hatching process can take only a couple of hours but can also last up to three days. Hatching of the scanned Marans chick dragged on for more than 36 hours. Including breaks the chick remained 24 of the 36 hours in the MRI system. "It was incredibly exciting to see how his chest worked and what tremendous efforts the chick had to make to get free," the project leader says. In different image series, about 60,000 MRI images were taken within the last 13 hours of hatching alone. From the very last 45 minutes of the hatching process, two videos were produced using the real-time MRI technology termed FLASH 2 and powerful graphics processing computers.
The resulting videos, with German narration, are included if you follow the link. The workout gives the chick a chance to initialize its muscles, so that within hours it will be capable of running beside its mother. Just enough air is included in a pocket near the tip of the egg where the beak is pointed for the chick to use for breathing until it breaks the shell open with its “egg tooth” designed for that purpose. As Biologic Institute's Ann Gauger says in Flight, “The whole process is so incredible; it transcends anything we know.”
Slowing Down the Flap
Particularly inspiring in the Illustra film are the slow-motion scenes of birds flapping their wings for takeoff, propulsion and landing -- especially the hummingbirds, whose wings can beat 1,250 times a minute. Now, in order to study flight for robotics, students at Stanford University have achieved a new record for slow-motion video of bird flight at 3,300 frames per second at full resolution, and “an incredible 650,000 at a tiny resolution."
Remember that hummingbird-like drone featured in the movie? The news from Stanford adds this support for Paul Nelson’s remark that the nano-hummingbird UAV is still “light-years behind the bird that inspired its creation.”
"The best way to prevent a small drone from spying on you in your office is to turn on the air-conditioning," said David Lentink, an assistant professor of mechanical engineering at Stanford. That little blast of air, he explained, creates enough turbulence to knock a hand-size UAV off balance, and possibly send it crashing to the floor.
A pigeon, on the other hand, can swoop down busy city streets, navigate around pedestrians, sign posts and other birds, keep its path in all sorts of windy conditions, and deftly land on the tiniest of hard-to-reach perches.
"Wouldn't it be remarkable if a robot could do that?" Lentink wondered. (Emphasis added.)
So, “In order to build a robot that can fly as nimbly as a bird, Lentink began looking to nature.” Some of the “never-before-seen intricacies of flight” that came to light using the ultra-high-speed camera are shown in the accompanying video clip. For instance, they found that hummingbirds have the “fastest body shake among vertebrates on the planet” -- at 55 times per second, much faster than a wet dog or mouse. Since thousands of birds have never been filmed with a high-speed camera, the team has opportunities to make groundbreaking discoveries every time they go into the field.
So Many Birds, So Little Time
Flight tells the amazing story of the Arctic Tern, its global migration spanning 44,000 miles a year. Many other birds accomplish remarkable feats of long-distance flight. One of them is the wandering albatross. This man-size, 10-kilogram heavyweight can stay aloft more than a month, almost never touching down, barely flapping its “long, elegant wings.”
A news story by the IEEE describes how a team from Munich Institute of Technology is studying albatross flight in hopes of improving robotic drones. They have begun mapping the curving flight paths of the birds for clues into how they use wind energy, instead of flapping, to go in any direction.
Exactly how the bird extracts energy from a horizontally blowing wind, however, was a puzzle. Scientists over the decades have attempted to find the solution using increasingly sophisticated computer simulations. Yet elaborate as they may be, these models can’t capture the full complexity of what’s happening. How do you simulate, for example, a sea troubled by strong winds that breaks up into irregular, meter-high waves, chopping the air into discontinuous blocks? Because of such unknowns, researchers long debated whether the shear wind field alone explained the soaring or whether there might also be other effects, such as gusts or vertical wind components.
Finally getting a grip on a solution by “an optimization method known as periodic optimal control,” the researchers “worked out a set of differential equations that describe the dynamics of flight.” Their model predicted that an albatross could stay aloft without flapping in a constant wind of 30 kilometers per hour (16 knots), using a series of dives and climbs alternating into the wind and with the wind in a spiraling path.
Then they traveled to Réunion Island, east of Madagascar, to test their model on live albatrosses, using geolocators attached to the birds’ feet. Since the albatross is a heavier bird, they could carry heavier instruments able to transmit data -- unlike those on the Arctic Tern used by Karsten Egevang’s group described in the Illustra film. The actual flight parameters of live albatrosses closely matched those in the computer model. This confirmation provides hope that future unmanned drones, using the model, could “surf the jet stream” efficiently, imitating the real-world capabilities of the wandering albatross.
The Illustra film briefly touches on evolutionary hypotheses for the origin of flight from dinosaurs. One problem not mentioned is that the digits in dinosaur feet differ from those in birds. “Feathered dinosaur” expert Xing Xu, with Susan Mackem, addressed this problem in Current Biology, “Tracing the Evolution of Avian Wing Digits.” In short, there’s not an easy solution:
A comprehensive analysis of both paleontological and developmental data suggests that the evolution of the avian wing digits may have been driven by homeotic transformations of digit identity, which are more likely to have occurred in a partial and piecemeal manner. Additionally, recent genetic studies in mouse models showing plausible mechanisms for central digit loss invite consideration of new alternative possibilities (I-II-IV or I-III-IV) for the homologies of avian wing digits. While much progress has been made, some advances point to the complexity of the problem and a final resolution to this ongoing debate demands additional work from both paleontological and developmental perspectives, which will surely yield new insights on mechanisms of evolutionary adaptation.
Don’t expect to cash in that promissory note any time soon.
These stories reinforce the intelligent design of bird flight, and illustrate the emptiness of Darwinian theories. Next time you see a hummingbird hover, or a sparrow or chickadee zoom across the yard to land perfectly on a twig, think about these real-world physics problems that challenge the understanding of scientists, and these abilities that inspire engineers to want to apply their own intelligent design to imitate them.
Image credit: Illustra Media.