Birds, unlike mammals, do not have separate exits for urine and feces. Both waste products are eliminated simultaneously through the cloaca. While mammals excrete nitrogenous wastes mostly in the form of urea, birds convert it to uric acid or guanine, which reduces water loss in comparison. The reason you don’t see birds urinating is because they don’t. Well, not in the traditional sense. Their pee is combined with their poop in a sort of two-for-one deal. To understand the process, we should first look at how mammals do it. Our kidneys pull excess nitrogen from our blood stream, convert it to urea and store it in the bladder, which then empties it out through the urethra.
Birds, like humans, have kidneys that do the important job of removing the nitrogen but, with the exception of the ostrich, birds don’t have a bladder or urethra. Instead, they convert the nitrogen into uric acid, which is then mixed with solid waste from the intestines and expelled. The uric acid also is why bird poop is white instead of brown.
So if you’ve seen a bird poop, you’ve also seen it pee.
