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You Asked ...

We answered! Experts reveal the shocking truth behind the mysteries of science.

Why is bird poop white?

Crystal Emerson, 16 Jonesport, ME

Bird poop is far more colorful than you think! The chalky-white paste called urate (made of uric-acid crystals) is a byproduct of bird kidneys. What you actually see is the color of the whitish crystals. Swimming in urate is a chunk of stool (solid waste). This piece is usually hard and worm-like, and gets its color from the bird's diet. Hues range from greenish for birds who feed on plant seeds and green vegetables, to brownish for brown birdseed, and reddish for strawberries. For shrimp-eating seabirds, it's pink!

To top it all off, bird poop contains a tiny sprinkle of urine. Why so little? "Aside from the ostrich, birds don't have bladders and can't carry a lot of water around. They'd be too heavy to fly," explains ornithologist (bird expert) Jerome Jackson at Florida Gulf Coast University. (By the way, the ostrich can't fly.)

Think bird poop is just waste? Think again. Veterinarians see it as an indicator of bird health. Abnormal colors like red urine and urate may be signs of internal bleeding. Brown urate may signal lead poisoning, and green or yellow urate may mean liver disease. Colorful indeed!

Why do we yawn?

Dorothee Pare, 17 Verdun, France

Scientists are still baffled by this gaping mystery. One possible explanation: "Yawning gets the brain in gear for changes in pace or activity," says psychologist Robert Provine, a yawn expert at the University of Maryland. "People yawn before they go to sleep, before they wake up, before they take a test." Yawning is also highly contagious, Provine adds. For example, seeing your classmates yawn may make you drop your jaw, too.

The most commonly taught yawning theory is that the brain signals for a yawn to give the body a quick jolt of oxygen whenever too much carbon dioxide is in the blood. Provine claims the theory is pure bunk. "This folklore has no basis and took on a life of its own," he says. To test his view, Provine had yawners inhale pure oxygen, then various air mixtures with high and low levels of carbon dioxide. Extensive test results showed the different air mixtures had absolutely no effect on the number of testers' yawns. This just proves the long-standing theory is nothing but hot air.
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Title Annotation:questions and answers on bird feces, yawning
Author:Chiang, Mona
Publication:Science World
Article Type:Brief Article
Date:Sep 6, 1999
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