Bird droppings defy expectations

Date:  September 24, 2019

Source:  University of Texas at Austin

For every question about bird poop, uric acid appears to be the answer.

Why are bird droppings so hard to remove from buildings? Uric acid.

Why are they white and pasty? Uric acid.

Why are they corrosive to car paint and metal structures? Uric acid.

These answers are based on the prevailing wisdom that ranks uric acid as the primary ingredient in bird "poop," which is comprised mostly of urine. (Birds release both solid and liquid waste at the same time. The white substance is the urine).

But according to Nick Crouch, a scientist at The University of Texas at Austin, uric acid can't be the answer. That's because there is no uric acid in excreted bird urine.

And after analyzing the excretions from six different bird species -- from the Great Horned Owl to the humble chicken -- he's pretty positive of that statement.

"It was easy to tell that what we had and that it was not uric acid," Crouch said.

The results were published in the Journal of Ornithology in August 2019. The study's co-authors are Julia Clarke, a professor at the Jackson School of Geosciences, where Crouch is currently a postdoctoral researcher, and Vincent Lynch a chemist and research scientist at the UT College of Natural Science.

Crouch studies bird evolution and biodiversity -- the chemistry of bird waste is not his usual research wheelhouse. However, Crouch decided to investigate the uric acid question after a conversation in 2018 with the late Jackson School Professor Bob Folk, who claimed that bird waste didn't contain uric acid.

"Sometimes you just get presented with a really weird question and you want to know the answer," Crouch said. "That was this -- I had no idea if [Folk] was right or wrong beforehand, but I was really interested to have a look."

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