One could assume they are intelligent and their little hands can bead strips of leather and tie feathers on each other , but there is another reason.
Particularly troll rogues.
Ever notice that all raptors seem to live in close proximity to one troll tribe or another, and most raptors have feathers on them.
When troll rogues come of age they have to go tie some feathers and beads on wild raptors to prove how sneaky they are. A lot of then get eaten, that's why you don't see so many.
A troll rogue told me this, and you know rogues are very honest.
You can trust them.
Especially the troll ones.