pluck vs molt vs broken feathers

Feather number 2. Found in a chair (now how on earth did it get there?) near the cage. It's a biggie---a clipped primary wing feather, full quill. only about an inch of actual feather on it and there is a small white band about halfway between the end of the quill and where the feather starts. Feather #1: The feather from the other day was clean at the cut line---it wasnt frayed, didnt appear to be chewed but there was a beak mark further up on the feather. He's also molting though other than these 2 feathers Ive not seen anything but an occasional down feather. Good news is he's got a TON of new quills popping out on tail, wings, etc...a lot of primary feathers starting to come in and his preening is less aggressive--not attacking the feathers so much as he's just doing what appears to be normal maintenance. He feels like a porcupine. How do I know what's normal molt, what's an accident (falling in cage) and what's feather destruction/plucking?

Having lived with a feather chewing GCC, I would say there are a few ways to notice. If the feather still has the entire quill, it likely fell out due to moulting - no quill usually means they've clipped it off (especially if you are finding little bits of feathers). If there is blood on the quill, its likely been plucked. If you are seeing any bare patches or down patches on the parrot, they are likely chewing or plucking as a normal moult might make them scruffy but it won't lead to any large patches of no/few feathers. If you find a lot of the same type of feather (i.e. all from one area), its likely plucking/picking as birds will moult with feathers from all around their body. Sometimes tail feathers get scruffy from being bumped against the cage/toys/perches. If feathers are coming out from an accident, they would probably have some other signs of injury as well as it would have to be a pretty solid accident to dislodge feathers.

From what you write above, it just sounds like a moulted feather. My GCC would sometimes pick up (or while preening he would dislodge) his moulted feathers and then scratch his own head with them or sometimes nibble them a bit before discarding them.