Like most folks from your area, you are grossly oversimplifying a fairly complex change of events. I say "from your area" because I spent more than 20 years there, working in the conservation field and managing rice fields, prairie and coastal wetlands. And by "there" I mean Eagle Lake, TX specifically. I know that town. Drove through it 2x/day for nearly 15 years. Knew the last two mayors personally. I ate 100's of hippos from the mini-Bucees', dropped off ducks at the pickers and I still tell folks that Austin's BBQ is the best in the state (because it is!).
Please take a minute and listen to what folks here are trying to tell you. Take the standard "I'm from Texas so I know everything" blinders off and actually listen with the intent to learn, not just the intent to respond. The decline in rice acres has nothing to do with the change in patterns of waterfowl. It has a lot to do with the rice market, especially those in other states and countries. It has even more to do with climate change. Think about how many other species' ranges are creeping northward. In the 90's you couldn't find a white-winged dove north of San Antonio and rarely north of Corpus. Now they have them in OKC. In the 90's armadillos were never seen north of OK, now they are in Illinois. In the 90's people in New England had only read about turkey vultures in books. Now they are in Canada. There is rarely one cause even if our simple human brains always want to think so.