They talk to each other. This is why calling skills are important for successful duck hunting. The feeding habits of ducks are somewhat like those of fish. There are certain times of day when they are likely to feed. The noon period is not as good as the other two except on dark stormy days.
Puddle ducks tend to feed at the crack of dawn.
Divers are a little later. Ducks in migration however, may be stocking up for the long flight in from the north. In this case they may eat anytime of the day or night. Ducks do feed every day. Just because you don't see any where you are, don't assume there are none in the area.