Birds and Gliding
Location: Outside U.S.
Date: Fall 2011
How can eagles fly without flapping their wings?
Let us go for some basics first about birds. In order to be a successful dwellers of air environment, birds have special adaptations that include
One set of organs where possible
special sacs (air bladders) which contain lighter than air gases
All the above things help maintain a required height by the bird.
Coming to your question, eagles and other larger birds first attain a specific height through flapping of their wings. Then they open their wings fully and glide on the air taking help from the modifications mentioned earlier. By filling more gases through their lungs into air bladders they keep themselves at a specific height. It is to remember that they are unable to go further high by gliding alone so they flap their wings in between to do that.
I hope you resolves your query.
Waseem S. Abbasi
Eagles, and some other birds, glide. They spread their wings and
catch thermal upward drafts of warmer air that rises under their wings. They
are able to keep gliding for significant distances, waiting to catch the
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Update: June 2012