What is guano used for?

Fertilizer: Bat and bird guano, rich in nitrogen, phosphorus, and potassium as well as calcium, manganese, iron and some copper.

Medicine: Historically some species have been harvested by humans for medical uses.

Cave paintings: Used to decorate the prehistoric European caves of Altamira in Spain with polychrome cave paintings

Energy: Bat guano used in the form of fuel to cook or provide light

Clothing Dyes: In the Inca Empire used as clothing dyes by Peruvian craftsmen for centuries