mikebr99 said:
Hawks don't have any move silently rating... though I think it should be up there with the Owl...
That's because they always launch off with that darn scretching sound. If they could just keep their beak shut...

Just kidding. The fact that do not have Move Silent skill is purely an oversight on the part of whomever designed them. Hawks, Owls, Eagles, Falcons, should all have Move Silent. All predatory swooping birds glide in or fall on the attack as opposed to flapping their wings. A lot of them also thermal glide when hunting their food.
Even Bats have Move Silently and they are actually quite noisy at close range because they constantly flap their wings.