What does DU do that would make ducks stop flying south, that a college educated outdoors man would actually believe? heat ponds? giant nets? perhaps mallard intercepting surface to air guided missiles? silo sized feeders with deer neutralizing tasers?
Did you ever shoot ducks over a pond that was fed with corn? They WILL NOT STOP coming in once they find it.
Go find a nice pond in the marsh with widgeon grass chocked full. The gray ducks will lit on your head and keep coming. I've seen it in the Sabine Wildlife area in the 80's. Damn gray ducks wouldn't stop coming all over us.
They now break up the ice and keep flows and ponds open for the ducks to stay. Plant more fields for the exclusive use of waterfowl and are probably responsible for those mallard/pintail hybrids ya'll like.
Moral is, as long as they got feed and they can get to it they ain't moving.