This is where the contingencies come in. You set your overall strategy—line up your spots—well ahead of opening day. Then when the shooting starts, you adjust and move as necessary to stay in birds.
Several factors will cause waterfowl to be drawn to an area, or abandon it. Perhaps the main one is food availability. If a spot offers choice feeding conditions, ducks and geese will likely find and utilize it. But if the food becomes unavailable (runs out, water drops out, water freezes, etc.), the birds will move somewhere else.
Rising and falling water is directly related to food availability. Rising water makes new food available to ducks, so the birds inherently come to a good, fresh flood. Conversely, receding water causes food to be less available and ducks to leave. A good rule to remember is to head upstream when a creek or river is rising and to reverse this direction when a high-water crest starts moving back downstream.
Hunting pressure can be a big influence on ducks' location. If pressure gets too heavy, the birds will abandon a preferred area. On some traditional shooting grounds where pressure is heavy, ducks will pile up in isolated patches of habitat, not because this is ideal habitat, but rather because these spots offer sanctuary from hunters.
The task, then, is to scout frequently as the season progresses to keep up with bird movements and to adjust your hunting strategy accordingly. There are several ways to do this both electronically and physically.
The Technological Age has opened the door to electronic scouting for waterfowl. The Internet offers a wealth of data. A hunter can chat with other hunters anywhere, checking on how many waterfowl they're seeing. He can effectively keep up with the migration through the DUcks Unlimited migration map. He can check waterfowl counts on area refuges. He can obtain the latest weather forecasts, monitor river levels, and run an entire intelligence-gathering effort from the confines of his computer station, literally keeping up with waterfowl movements from one day—or one hour—to the next.
Many waterfowl hunters employ another technological boon: the cell phone. Now a hunter can stay in touch virtually anywhere he goes. If he's hunting one spot and having no luck, he can dial up a buddy who's hunting somewhere else and inquire about his success. If he's into birds, the calling hunter knows it's time to move. [see DU mobile apps]
The key to all this electronic give-and-take is having a set of reliable contacts, and this takes time to build. Experience will teach you whom to trust—whose information is credible.