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Hummingbird flight

From:

Jim & Kathleen Wilson

Reply-To:

Jim & Kathleen Wilson

Date:

Sun, 3 Jul 2005 18:50:26 -0400

      I found this short article on the Scientific American magazine website 
and I thought it was worth sharing.  This article is freely available to all 
who access the site...
          http://www.sciam.com/article.cfm?chanID=sa003&articleID=0002A840-B9B9-12B9-B9B983414B7F0000


      Jim Wilson
      Queenstown,MD

      High-Tech Pictures Reveal How Hummingbirds Hover





      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