Actually, a duck's wing *can and will* break a human arm. You piss off momma protecting her babies, and you tell me how dangerous the vicious bastards are.
Not as dangerous as geese or swans. Geese are vicious. And swans... swans have actually killed people. Well, that or knocked them unconscious and left them to drown. Depending on how dramatic you wanna be.
@Ted: it's a monty python joke. Where have YOU been for the last forty years?