Ears

just average human-like ears

Wings

apparent at birth
(excluding flightless bird species, emu, ostrich, penguin, dodo, penguin, cassowary, ect)
vary from small-medium-large

wings aren't fully developed until early adolescense

Feather Coverage

Feather color is limitless and based off any real bird species
two Harpy of the same bird species can have completely different feather coverage on the body

Tails

General shapes(Varys by species of bird)

Feet

examples

Raptor: eagles, hawks, owls, falcons,ect birds of prey
Webbed: ducks, swans, geese, ect water fowl
Perching: Songbirgs, Crows, Pigeons, Parrots, ect
Walking: Chickens, Peacocks, pheasants, ect land fowl
Flightless: Emu, Cassowary, Dodo, ect Flightless(webbed): Penguins