Nitrogen Excretion by Turkey Vultures

Abstract

The proportions of nitrogen (N), as urate-N (76.1%), NH3-N (16.4%), and urea-N (7.5%) in the urine of fasted Turkey Vultures, are similar to those found in the urine of domestic chickens and ducks, the only other birds for which comparable data are available. Vultures show an adaptive increase in the percentage of urinary N excreted as urate (up to 86.8%) and a decrease in NH3-N (down to 8.9%) and urea-N (down to 4.3%) in the period after feeding on meat. These alterations in the proportions of nitrogenous wastes increase the efficiency of N excretion; fed birds excrete 4.8 times more N per milliliter of urinary water than fasted birds. The efficiency of N excretion during the 1.5-h period after feeding is comparable to that of the most efficient mammalian excretory systems.