Urine is an aqueous solution of waste electrolytes and metabolites excreted by mammals, birds, reptiles, fish and amphibians. Although urine is excreted as a paste by most birds, it is commonly excreted as a fluid varying in color from clear, when dilute, to a dark amber, when concentrated. Urine is produced by the kidneys, and plays a vital role in maintaining homeostasis by removing excess water, electrolytes such as sodium,...