Spherical Urine in Birds: Petrography

See allHide authors and affiliations

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


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.

Stay Connected to Science