When is the term "droppings" used for faecal matter, and when is it not applicable?
I can see the term being used for rats, insects, or birds, but can't envisage it being used for humans or cows or elephants. Does size and/or moisture content play a role?
The Free Dictionary, citing Collins English Dictionary, says
the dung of certain animals, such as rabbits, sheep, and birds
which suggests there's a logic as to when the term is used, but isn't too specific.