Cloaca

Birds, like most vertebrates, apart from many mammals, have a cloaca. Cloaca is Latin for sewer and is the combined intestinal, urinary and genital opening. It’s just underneath the tail.

Birds have no teeth and often rely solely on very acidic stomachs to digest their food. It’s why bird poo can strip the varnish off your car bodywork. They’re also fabulous at conserving water so they don’t have to drink large volumes and can keep their flight weight down. That means they produce white uric acid crystals in a paste rather than vast quantities of watery urine.

All of which explains this photograph.