Why is chicken guano white?

[LateComer]

What is the white stuff in chicken excrement? Just wondering.

[Skwerl]

I don't know about chickens, but I've read that the white stuff in bird droppings is actually their urine, and the black/brown lump is the real poo.

[Colibri]

All birds, like reptiles, excrete uric acid, which is white and relatively insoluble. Mammals excrete urea, which is more soluble and requires a lot of water to flush out. The white in bird droppings is their semisolid "urine."