Either Pyoko is lying through her teeth or the crows in that neighbourhood are metal as fuck
Birds can be fucken savage. Back on the farm I'd always bring a pitchfork with me when collecting eggs. We kept a rooster for breeding and that fucker went for me every time I entered the pen. I'd use the pitchfork to pin his neck to a straw bale before entering the coop. Occupying an enclosed space with pissed off 25lb bird is all sorts of not fun.
Pyoko appears to have gotten some human clothes back in 1980.
Also: humans use feet for propulsion (walking) & hands for manipulation. Birds use wings for propulsion (flying), having both feet & a beak for manipulation. You might be surprised by how much they can do.
I mean its fine for dumb monsters who just eat people but not an intelligent race.. she couldnt feed herself- she couldnt have dressed herself.. couldnt build or make anything.. etc etc.
I remember watching an interview with an armless woman, one part of which touched on her being able to dress herself with only a stick attached to a suction cup for assistance. She'd also managed to ride horses, which is how she died(her foot got stuck in the stirrup when she fell out of the saddle).
But you're right that harpy civilization wouldn't be building anything too precise on its own(coarse building is just fine, given that birds tend to, y'know, build nests).