Have you ever wondered if birds pee and why bird poop is white? We asked an expert to break down the details of bird waste.
Do Birds Pee? The Science of Bird Poop
Updated Sep. 12, 2024
On This Page
Do Birds Produce Urine?
If you’ve ever had a pile of white and brown splat on your windshield, you’ve probably thought, What, exactly, was that? You know it came from a bird, but you might not know how, or why, or the most accurate human term to describe the rapidly drying stain on your car. And at some point, you’ve probably then wondered: Do birds pee?
It’s a question both simpler and more complex than you might imagine. “Well, it depends on how you define pee,” David Wiedenfeld, senior conservation scientist with American Bird Conservancy, says. “It’s a question that people ask because they’re worried about birds peeing on them. You can get a bird pooping on you, but it’s like, ‘I don’t ever get peed on by a bird.”
Learn the basics of bird anatomy.
The Nitty-Gritty of Nitrogen
According to David, the process of bird excrement—and the differences between bird droppings and what we would consider pee—come down to how we and birds process extra nitrogen. As he explains, both birds and humans consume extra nitrogen. We both convert it to ammonia as a result of eating protein. And getting rid of nitrogen waste is important for both birds and humans, because ammonia can be toxic.
“What mammals do is that we convert it to urea, which is water-soluble, and we pee that out,” David says. “Birds, though, do it differently. Instead of producing urea, they convert ammonia to uric acid. Uric acid is related to urea; it’s not very acidic. It is not soluble in water. It forms crystals, and birds accumulate the crystals, combine it with their poop, and poop it out at the same time.”
Bird senses: can birds smell or taste their food?
The Benefits of Uric Acid
Interestingly, David says that birds’ reptilian heritage shows through their excrement. Lizards, iguanas, crocodiles, and other reptiles release their waste the same way. The way in which they get rid of their ammonia, David says, makes it easier for them—and for birds—to live in dry environments.
“You get into the southwestern U.S., and some birds never really drink,” he says. “They barely need to drink water, although they will sometimes, if it’s available.”
Why? As David puts it, uric acid is not soluble in water, so birds don’t have to drink water to get rid of it. When humans get rid of urea, they have to dissolve it in water. When we go to the bathroom, we then get rid of some of our water.
Because birds produce uric acid, which converts into crystals and doesn’t use water during the conversion process, they’re able to hold onto their water for longer than humans. He also explains that it is thought uric acid could help birds keep their weight low, because they don’t need to take in much water to make it.
Learn all about a hummingbird’s metabolism and heart rate.
Why Is Bird Poop White and Brown?
When you see that a bird has chosen your car as its outhouse, you’ll typically see a blotch of white combined with some brownish chunks. As David explains, that two-colored appearance is a direct effect of the way birds process their waste. The ‘white stuff’ is uric acid—the birds’ converted nitrogen waste—and the ‘brown stuff’ is what we would consider poop.
David breaks it down further. “Their ‘poop,’ is things that aren’t digested, basically,” David says, of bird droppings. “If you eat something that’s high in fiber, your body can’t digest all of that, and some of it will be pooped out.
Birds do that, as well. If they eat something that has a portion they can’t digest—for example, an insect’s exoskeleton—they poop that out, but they combine it with uric acid and do it all at once.”
That ‘all-at-once’ release produces the two-toned droppings that we often find on cars, buildings, and sidewalks.
Because uric acid isn’t soluble in water, you might have a tough time scrubbing it off your windshield with water alone. Car dealers recommend a variety of solutions, ranging from a combination of baking soda and water to specialty cleaning wipes.
Next, find out where birds sleep at night.
About the Expert
As senior conservation scientist for American Bird Conservancy, David Wiedenfeld has worked on research pertaining to bird populations for decades. He served as director of research at the Sutton Avian Research Center, and he also served as head of the department of vertebrate ecology at the Charles Darwin Research Station in the Galapagos Islands. He holds a doctorate in biological science from Florida State University, and his favorite bird is the swallow-tailed kite.
Sources
- Audubon, “What Makes Bird Poop White?”
- Natural History Museum, “Do Birds Pee?“
- Northside Ford, “5 Surefire Ways to Get Dry Bird Poop Off Your Car“
Originally Published: September 12, 2024
