Car windshields, monuments, balconies and, for the unluckiest, clothes: they are all targets of bird “poop”, that whitish substance with darker, greenish or brown parts. But what is it exactly? Is it feces or is it pee? And why is it white? The short answer is: both. Birds, in fact, do everything at once for evolutionary and adaptation reasons.
Unlike us humans and other mammals, “feathered” birds do not have a bladder to store urine, nor a urethra to expel it. Having a bladder full of liquid would in fact be a burden useless And disadvantageous for those who must fly. The anatomy of birds therefore provides only one way out to carry out their needs: the cloaca. In this single orifice, located in the terminal part of the intestine, both the solid waste from the digestive system and that from the urinary system flow together, which are expelled in a single “two in one” solution.
If we look carefully at what we find on the bodywork of the car, we will notice two distinct components. There darker part (often green or brown) corresponds to the real ones I did and its color depends on the animal’s diet. There white partcreamy and sticky, is instead the equivalent of ours urine.
The difference lies in chemistry. While mammals eliminate nitrogenous waste in the form of urea (which requires a lot of water to dilute), birds convert them into uric acid. This substance needs very little water to be expelled and precipitates in the form of insoluble white crystals or urates. This strategic “move” allows the birds to reduce water loss and, at the same time, of travel light. Unfortunately for us, the chemical composition of these crystals makes the stain difficult to dissolve with plain water.
However, not all bird droppings end up splashed on the ground. There is an ingenious system called fecal baga tough mucous membrane that surrounds the feces of nestlings (the young still in the nest). It works like a real biological garbage bag that allows parents to take the needs of their little ones with their beak and take them away far away. This serves to keep the nest clean (avoiding infections) and to prevent predators from smelling it.
Finally, it ostrichis the exception that proves the rule. Although it has a cloaca like other birds, its physiology is different. This giant can expel theliquid urine separately from solid feces. He, unlike his flying cousins, does not need to be light, so he can afford the “luxury” of peeing like mammals.
