A duck goes quack.

Carl and I took an outing with our playgroup to a local park. After the kids are done playing, we all walk over to the pond and let the kids feed the ducks. As the bread was flying, I walked with Carl so he could get really close to one of the ducks -- a duck with a mohawk. Carl stared at this particular duck for a long time. The duck saw him staring, stopped eating, and let out a big 'ol quack. Carl was startled and screamed bloody murder for a few seconds. I told him that you never want to mess with a duck that has a mohawk. All ducks go quack, but there is something different about the quack of duck with a mohawk. QUACK!