For characterization try emulating Ravens to Cockatiels they have alot of personality but has the discipline of 4 year old.
Or if you have a cat, just think of it as a furry asshole with wings (a.k.a a cat).
But if you want more historically closer harpies, they were the personification of storms and served as messenger for Hades, where they had the job of snatching away children and people's souls. Being entities of the storm they also answer to the call of Zeus (but who really doesn't in greek mythology) and as is usual in the hyperborean lore of the greeks they are born from Oceanid (ocean spirit) and some ancient sea deity which also made them siblings to Iris the messenger goddess. Additionally harpies were also considered the mothers of horses. With horses being born from Zephyros (god of the wind) and a harpy. With all that behind, you can probably bullshit a harpy into pretty much anything you want really.