They have wings and beaks. That's it, that's where the similarities end. You know how a finch acts absolutely nothing like an eagle? Yeah, that's about how pointless it is to try to 'describe' a 'Harpie'.
Unless you're asking about Mrs McKeerlē, in which case I'd just describe her as a 'Harpie'.
Crumpled History Test Paper
Lyrique Fey. 3rd Year. Confiscated 14th Day Glittersea Moon
Action Taken: Detention. Mother away for work. Contacted parental guardian, but he "Thought it was quite witty, actually."