by 
The Curious Bag
-
Birds have white and brown stool because the urinary and digestive tracts both empty into the cloaca, and the urine and feces are mixed.
Cloaca
The cloaca is the common exit of the digestive, urinary and reproductive systems.
Bird Urine
Birds and reptiles have solid urine. This type of urine is composed of uric acid and forms the white portion of the droppings. The liquid portion is mucus, which allows the solid urine to exit the bird's body. Urine is formed by the liver and kidneys.
Bird Feces
The feces is the brown portion of the droppings. Feces is formed by the digestive tract.
Why Solid Urine?
The solid urine of reptiles and birds is an adaptation for growing in an egg with a thick shell. Liquid urine would not be able to escape the egg and would drown the fetus. Solid urine is more concentrated and can be contained until hatching. Concentrated urine and feces is also an adaptation for flight, as it weighs less than liquid.
Color Variations
There may sometimes be far more of one portion of the stool. As long as the bird is getting adequate food and water, this is nothing to worry about. Peculiar colors in the uric acid, such as green, are a sign of serious medical problems, but in the feces are usually related to the bird's last meal.
Source:
Functional Anatomy and Physiology of Domestic Animals; William O. Reece; 2005
Animal Diversity; Cleveland P. Hickman, Jr., et al.; 2007
More Information:
RELATED QUESTIONS
Copyright 2023, Wired Ivy, LLC