it makes great fertilizer. from Wikipedia
It is an effective fertilizer and gunpowder ingredient due to its high levels of phosphorus and nitrogen and also its lack of odor. Superphosphate made from guano is used for aerial topdressing. Soil that is deficient in organic matter can be made much more productive by addition of this manure. Guano consists of ammonia, along with uric, phosphoric, oxalic, and carbonic acids, as well as some earth salts and impurities. The high concentration of nitrates also made guano an important strategic commodity. In fact, the War of the Pacific between the Peru-Bolivia alliance and Chile was primarily based upon Bolivia's attempt to tax Chilean guano harvesters.
