Duck migration has changed. It changes and is different every year! There are two factors to consider:
1. What forces a mallard to come south?
2. Why does he go where he goes when he does come south?
Mallards will stay as far north as they possibly can. Lack of food and/or lack of open water will force 'em south - nothing else. A lack of food can occur with a snow fall of six inches or more, because that covers the food. A lack of food can also occur if the ducks eat out the available food. They will eat it out only if the temps are low, forcing them to eat more. Low temps will freeze backwater, but ducks can and will keep a larger body of water open by using it. They can dry feed then hit the open water. Certainly no-till farming has made more food available than before, when it was plowed under before the migration started. Snow will cover no-till food and force the ducks south to find food.
Trouble is, the last few years have been unusally warm and dry up north, where the ducks stay unless forced south. The weekend of 01/24-01/25 2004 was the first snowstorm to cover the Miss. flyway from Missouri to Canada with any appreciable snow. The following image is useful as a tool to figure out where the ducks are:
http://www.weatherimages.org/data/imag310.html
The majority of the snow shown in the upper Miss. valley just appeared over the past few days.
To say that ducks come south even when it's warm is thinking locally, while a duck reacts flyway-wide. Sure, you may have shot ducks in your shirtsleeves in years past, but you've gotta know what the weather was up north that year to figure out what forced those ducks into your warm-weather blind. There have been a lot of years when the upper Miss. valley was hammered with snow, while the lower Miss. valley basked in relatively warm weather. The local weather has little to do with whether or not the ducks migrate, just like local hunting pressure has NOTHING to do with whether a duck migrates. A duck 200 miles (or less) north of you has no idea whether you're hunting or not.
Once the ducks start south, why do they go where they go? Food and water. Arkansas is a good example of a state that has been dry for the past few years. Eastwoods blames the lack of ducks in the woods on rice field availability. I've hunted over there for years, and until the Cache and White Rivers put water in the woods, ducks aren't going to be in the woods - because they're dry! Where I found flooded green timber in Arkieland this year, we whacked ducks (public lands, too) once we paid attention to the ducks. Mississippi has been relatively dry as well. Both states have suffered over the past few years because the Mississippi River hasn't flooded out, which raises all of the feeder rivers and puts water everywhere. Cotton has been planted in many areas of the southern Miss. valley, and this hurts your local duck numbers. Ducks will overfly a dry area or one with little or no food, until they find food and water.
I don't worry about imprinting much. Once the migration is forced to start, they will find food and water. I hunt a small place that only floods once every 5 to 10 years. Very rarely does it hold water, but whenever it floods, the ducks find it - almost overnight if there is a reason for them to be migrating in the first place. And this spot is a good 200 miles from the Miss. River, yet will be covered in ducks when it floods even if it hasn't held a duck in the past 10 years.
DU should be applauded for doing what their membership requested. They listened to the DU members who b*tched during the '80's because all of DU's money was spent in Canada. Many of the members thought that wintering habitat in the US should be where some of the money be spent. DU responded and did just that. Now, they are being blamed for poor hunting - because they listened to their members and did what they were asked to do. 10 million acres that are covered in snow at least six inches deep won't support any ducks! DU's land would have to support the ducks for 6 months to affect the migration, not 30 days. The migration starts about Sept 1 up north. According to gyver's numbers, the 2 million acres DU has conserved in the US would support 10 million ducks for one month. Nationwide there are 36 million ducks, so the DU land could support all of those ducks for . . . about 7 days, from 09/01 til 09/07. If you take his other approach - "if their is 5,000,000 acres north of us that works out to 25,000,000 ducks for 30 days" - and realize that nationwide there are 36 million ducks, that would mean that, at best, DU could support those ducks from 09-01 till about 09-25. Then who you gonna blame?
It's the weather, plain and simple. More importantly, it's the weather up north, not the weather in your backyard. There are no conspiracies among DU, northern states, FWS or anyone else to short-stop the ducks, or feed the ducks. Blame the weather, nothing else.
Why on earth does anyone think that changing local hunting seasons would in any way affect migrations? Quit thinking locally, and start thinking from a duck's perspective. A duck in Michigan or Kentucky or Tennessee has no idea whether the season is open in Miss. (or how much hunting pressure there is). To a duck, hunting season lasts five months long, regardless of whether *you* get 60 days to hunt or 30. Duck season opens about Sept. 01 and ends in late January - five months later. Longer if you're a teal or pintail and migrate to Mexico where they're shot at until March or April!
Now, ya'll can take turns telling me how wrong I am!