RAB87 said:
I'm skeptical that flooded corn is the driver. That shouldn't be impacting all species. Also, there would be plenty of hunting social media showing massive waterfowl concentrations on flooded corn. As others have noted, an unusually warm winter likely weighs in. However, my hypothesis is that the biggest factor is habitat loss. Look at the Katy Prairie for example. Used to be the snow goose Mecca. Now it's all suburbs and the only waterfowl left are the ones painted on the water tower next to I-10. I believe this kind of habitat loss is the root of all the earth's environmental problems, including the heartbreaking decline of ducks.
It's not just flooded corn, but the entire CRP programs up north that are keeping birds north. Turns out that they don't care all that much about temps - they concregate where food is plentiful, and right now the plains and lower midwest are flush with food, good nesting habitat and a lack of cold enough weather to cover the food/nesting habitats and force them further south.
Same reason we have hardly any geese on the Texas coast anymore - no reason for most of them to make it all the way down here when they can stop halfway and have everything they need to survive and thrive during the winter months.
I posted an article about this probably 15 years ago now - it was a noticeable issue then, especially with the goose migration. At that time there was a single county in Arkansas that wintered more snow geese than the entire Texas coast did, and that was mostly a function of the fact that there was abundant food where historically there wasn't before. I want to say at that time there were less than 250k geese counted along the Texas coast when we once had numbers in the multiples of millions.
Doesn't help either that we have steadily chewed up the prairies to build master planned communities and the rice farming industry down here is a shell of what it once was either. But that doesn't have nearly the impact that the changes up north have had that keep the birds from making it this far south to begin with.
EDIT - here is the article
https://www.chron.com/news/article/fewer-geese-making-texas-their-winter-home-5126404.php