What is the main nitrogenous waste excreted by birds and reptiles?

💡 Solution & Explanation

Birds and reptiles excrete nitrogenous waste primarily as uric acid because it is relatively non-toxic and can be expelled as a thick paste or solid precipitate with minimal water loss, facilitating embryonic development inside shelled eggs. Mammals excrete urea which requires moderate water for dilution, while aquatic organisms excrete highly toxic ammonia directly into the surrounding water. This physiological adaptation is a textbook example of evolutionary water conservation in terrestrial fauna.