Why is bird poop whitish?

The white stuff that you find splattered all over your windows isn’t bird poop. It’s actually bird urine. The poop is the small, black blob that you often find in the middle. While mammals poop and pee from separate places, birds eject all their waste products from one exit point: the cloaca.

The bird changes the liquid urea into uric acid, which forms a thick, white paste. The black poop is excreted at the same time, and therefore shows up in the centre. However, not all birds behave in this way. The ostrich expels urine from its mouth before defecating from its cloaca… gross!