Reports

Spherical Urine in Birds: Petrography

Science  19 Dec 1969:
Vol. 166, Issue 3912, pp. 1516-1518
DOI: 10.1126/science.166.3912.1516

Abstract

The white part of bird droppings (the urine) consists of microscopically uniform spheres 2 to 8 micrometers in diameter. Strange behavior of the spheres in polarized light indicates that they are often made of a spiraling arrangement of crystals that are particularly well revealed by the electron microscope. Bird urine has a varied composition, and x-ray analysis shows that it does not consist largely of uric acid, as has frequently been parroted.

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