Excretion in birds
In the birds, the ureters transport the urine to the cloaca, which is the common collection site for digestive, reproductive and urinary organs. There is no urinary bladder in birds.
- Urine formation in birds is almost similar to the mammals but still then there are some notable differences:
- Presence of two major types of nephrons which are functionally different.
- Presence of renal portal system.
- Formation of uric acid instead of urea as the end product of nitrogen metabolism.
- Post renal modification of the urine in the ureter.
Types of Nephron in Birds
- Avian kidneys are characterized by having two major types of nephrons:
- Reptilian type and
- Mammalian type
The reptilian type nephrons are located in the cortex and it lacks the loop of Henle. It has no capacity to concentrate the urine, i.e., there is no tubular transport system and whatever solute and water is present in the filtrate, directly passes to the cloaca.
Mammalian type of nephrons have well defined loop of Henle. It has the capacity to concentrate the urine. In this tubular transport system is present.