The ducks at MSU have no fear of humans. In fact they can be pretty damn impatient if you're not quick enough on the draw. The one behind my right leg is pecking at me trying to get me to hurry up and turn his way. If you wait long enough, the closest ones will peck at your pantlegs until you give in and feed them.
I discovered one way of stopping the pecking...throw a handful of bread the other direction. It works for about ten seconds. At least they don't draw blood.