@PonyPon
I have a different thought.
The hippogriffs became what they did because the Pearl of Transformation was crafted by Calliope Crash, the First Siren, as a means to make more of her kind. It is, or
was, where new sirens came from. Novo made a few adjustments, but not many.
(And if you thought the sirens were unhappy about your version of events, imagine how they feel about this scenario.)