INGRATITUDE.
Pigeons are a symbol of ingratitude; for when they are old enough no longer to need to be fed, they begin to fight with their father, and this struggle does not end until the young one drives the father out and takes the hen and makes her his own.
CRUELTY.
The basilisk is so utterly cruel that when it cannot kill animals by its baleful gaze, it turns upon herbs and plants, and fixing its gaze on them withers them up.
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.