feces vs guano

feces

noun
  • Digested waste material (typically solid or semi-solid) discharged from a human or mammal's stomach to the intestines; excrement. 

guano

noun
  • Dung from a sea bird or from a bat. 

  • Coccothrinax borhidiana, a variety of palm tree indigenous to Cuba. 

How often have the words feces and guano occurred in a corpus of books? (source: Google Ngram Viewer )