> Regarding Shag's discussion of the importance of guano.
The oeuvre of Anthony Trollope owes something to guano. That marvelous creep Ferdinand Lopez (The Duke's Children), a villain for whom you almost root in spite of himself and his creator, depends at a crucial point on a speculation in guano. (Spoiler: it doesn't turn out well.)
IIRC Melmotte, another fully-human creep, in The Way We Live Now, has a guano connection, but I don't remember the details.