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High-Tech Pictures Reveal How Hummingbirds Hover

_{ImageCourtesy
of Oregon University}

Hummingbirds are famous for their hovering ability, which lets them linger in front of flowers and feast on their nectar. But just how the creatures manage to stay aloft has intrigued researchers for years. New findings published this week in the journal Nature indicate that when it comes to flying, a hummingbird's style is halfway between that of a bird and an insect.Previous investigations into the flight of the hummingbird had suggested that it could be employing the same mechanisms as insects, which often hover and dart in a manner similar to the bird. "But a hummingbird is a bird, with the physical structure of a bird and all of the related capabilities and limitations," explains Douglas Warrick of Oregon State University. "It is not an insect and it does not fly exactly like an insect." To unravel the hummingbird's aerial secrets, Warrick and his colleagues used a technique called digital particle imaging velocimitry (DPIV). Usually employed by engineers, DPIV uses microscopic particles of olive oil that are light enough to be moved to and fro by the slightest changes in air currents. As a pulsing laser illuminates the droplets for short periods of time, a camera captures them on film. From the resulting images, the scientists determined exactly how the bird's wings move the air around them.

The results indicate that hummingbirds get 25 percent of their lift capacity from the upstroke beating of their wings; the other 75 percent of the lift comes from each downstroke. Insects, in contrast, divide the work equally, getting 50 percent of the lift from each, and other types of birds rely solely on the downstrokes. "What the hummingbird has done is take the body and most of the limitations of the bird," Warrick says, "but tweaked it a little and used some of the aerodynamic tricks of an insect to gain hovering ability." --Sarah Graham

New Movement in Parkinson's
So far researchers and clinicians have found no way to slow, stop or prevent Parkinson's disease. Although treatments do exist--including drugs and deep-brain stimulation--these therapies alleviate symptoms, not causes. In recent years, however, several promising developments have occurred. Such findings are feeding optimism that fresh angles of attack can be identified.

Scientists Breed Sturdier Rice Plants
Some 23 percent of all the calories consumed by the world's population come from rice, making it one of the most important foodstuffs on the planet. Now scientists in Japan and China report that they have developed a hardier rice plant that resists collapsing in inclement weather, leading to higher crop yields. The results, the researchers say, could "pave the way for a new green revolution."

Scans Show How Hypnosis Affects Brain Activity
The word "hypnosis" tends to conjure up images of subjects partaking in silly activities they might not otherwise agree to. But over the past few decades, scientific study of hypnosis has begun to identify how the approach can work to alter processes such as memory and pain perception. According to a new report, hypnotic suggestions regulate activity in certain regions of the brain and can help it manage cognitive conflicts.

Chemical Test IDs Currency Associated with Drugs
Scientists have developed a new weapon for the war on drugs: a novel method for tracing the illicit substances on currency. Study results indicate that the pattern of contamination on money recovered from drug-related crime scenes is significantly different than that seen on bills in regular circulation.

Psyching Out Evolutionary Psychology: Interview with David J. Buller
Philosopher of science David Buller has a bone to pick with evolutionary psychology, the idea that some important human behaviors are best explained as evolutionary adaptations to the struggles we faced tens to hundreds of thousands of years ago as hunter-gatherers.

Gard Otis, a professor of environmental biology at the University of Guelph in Ontario, Canada, who studies bee behaviour, ecology and evolution, explains

Bees buzz for two reasons. First, the rapid wingbeats of many species create wind vibrations that people hear as buzzes. The larger the bee, the slower the wingbeat and the lower the pitch of the resulting buzz. This is a phenomenon of the wingbeats and not specifically of bees--some flies, beetles, and wasps also have buzzy flight caused by their wingbeats.

In addition some bees, most commonly bumblebees (genus Bombus), are capable of vibrating their wing muscles and thorax (the middle segment of their body) while visiting flowers. These vibrations shake the pollen off the flower's anthers and onto the bee's body. Some of that pollen then gets deposited on the next flower the bee visits, resulting in pollination. The bee grooms the remainder of the pollen onto special pollen-carrying structures (on the hind legs of most bees) and takes it back to the nest to feed to the larvae.

When bumblebees vibrate flowers to release pollen, the corresponding buzz is quite loud. Honeybees (genus Apis) are incapable of buzz-pollination and are usually quiet when foraging on flowers. As an aside, some flowers are adapted to pollination by pollinators capable of "buzz-pollination." Tomatoes, green peppers and blueberries all have tubular anthers with the pollen inside the tube. When the bee vibrates the flower, the pollen falls out of the tubular anther onto the bee. Consequently, bumblebees pollinate these crops much more efficiently than honeybees do.


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