Ryoung26, some days the ducks aren't flying. It can be anything from temperature, to "blue bird" days (sky blue and sun shining), to little wind or low tide. Pitt marsh is not my area but where I go you may not see the ducks until you go to a certain area and only if you can spend the time to sit and watch for an entire morning or afternoon. Your time driving past an area may have been the wrong snapshot of time to see them. Almost all animals are more active at dawn or dusk. Basically changing conditions prompt them to move, otherwise you have to jump them where they are resting. If you see them flying, they are trafficking from an area of rest to feeding or vice versa or just for social reasons.