This is a cool article about hunting the migration from the DU website:
"Hunting Flight Ducks
Tips for hunting waterfowl that are on the move
•Food resources, winds, and hunting pressure can move birds from one area to another.
•Creative decoy strategies and aggressive calling help mid-latitude hunters late in the season.
By Matt Young
This is a time of transition for migratory waterfowl across North America. The first major snowstorms and Arctic blasts of the year begin to plunge across the Canadian border, and rapidly declining day lengths and progressively colder weather trigger the migration of waterfowl from the breeding grounds. This is the time of year that waterfowlers in mid-latitude states live for, when every major cold front can bring new flights and hot shooting.
Mike Checkett, a Missouri native and communications specialist at DU national headquarters in Memphis, says most waterfowl migrate primarily in response to food availability. "Ducks that feed largely on aquatic vegetation, seeds, and other natural plant foods found in shallow water areas, including green-winged teal, gadwall, wigeon, and wood ducks, are typically the first to migrate, because they can quickly lose access to their food supplies during a sudden freeze. The food resources used by migrating mallards, black ducks, scaup, and other divers, which feed on waste grain in dry fields or on mollusks and crustaceans in deep, open lakes, are less vulnerable to cold weather. These birds don't have to migrate until deep snow covers the fields or frigid temperatures freeze big water areas."
Hunting the Migration
For waterfowlers who hunt along waterfowl migration corridors, timing is everything. "To be successful at mid-latitudes you have to be flexible enough to drop everything and go when the weather is right," Checkett says. "While I was conducting my master’s research on state waterfowl areas in north-central Missouri, I noticed that new ducks would start to trickle in a day or two ahead of major cold fronts, and even more birds would pile into management areas as the front was blowing through. However, while the peak of the migration usually occurred with the front, the best hunting occurred on clear, cold days immediately after the front had passed."
"Migrating waterfowl take full advantage of tail winds," Checkett continues, "and many of the birds will ride them as far as they can until the wind shifts. On north wind days, you'll often see a lot of ducks moving south, but many of them keep on going. From my personal experience, the best time to hunt is following a frontal passage, when the wind has just started to shift from north to the south. Migrating flocks know it's time to stop when they hit a headwind or the wind subsides.
At such times, Checkett recommends waterfowlers use large decoy spreads and aggressive calling to draw in passing flocks. "Nearly all migratory birds use flocking as an adaptive strategy. When ducks first arrive in an area, they are often drawn to large wetlands in search of large concentrations of other ducks that signify safety and the availability of food. They respond to calling for the same reasons. "