Reptiles and birds excrete waste as an insoluble white solid that is called uric acid how does this them to maintain internal homeostasis in hot climates

The correct answer is by retaining water.

Explanation:

Eliminating uric acid as a waste assists the birds and reptiles in sustaining the internal homeostasis in hot weather by reducing water loss or by retaining water. The reptiles and birds transform the toxic ammonia to uric acid, while on the other hand, the mammals transform ammonia to urea.  

Generating uric acid in place of urea is less toxic, and at the same time, excreting uric acid minimizes loss of water that plays a significant role in hot climatic conditions.