Well, it says that bird poop contains keratolytic or also knows as urea: an organic compound that works as a natural skin moisturizer.
The poop droppings are collected, sanitized then turned into a powder. The powder is later on mixed with water to create a paste, and the paste is used as a mask.
You can purchase the mask or the poo based soap on amazon along with other related beauty products, under the Japanese name of the facial ” Uguisu Poo Uguisu No Fun”.