Birds have a single opening for passing faecal and urinary waste, and eggs or sperm, called a vent. Inside the vent, the cloaca is divided into 3 sections, which can be remembered using a CUP acronym.
· Coprodeum is the first (most cranial) section. This is where the rectum opens into.
· Urodeum is the second section. This is where the ureters and the oviduct (or in males, the deferens duct) open into.
· Proctodeum is the last section, which opens out to the vent to excrete droppings (which are combined faeces and urates/urine).
There is no urinary bladder or urethra.
Image reference and further reading:
Taylor WM. Clinical Significance of the Avian Cloaca: Interrelationships with the Kidneys and the Hindgut. In Speer BL. 2015. Current Therapy in Avian Medicine and Surgery 1st Ed.
