The number of wild geese wintering along the Texas coast has steadily decreased over the last 15 years from more than 1 million to fewer than 200,000.

The population decline can partly be attributed to the waterfowl’s ability to adapt. Snow geese originally fed on green vegetation, but adapted to feeding on waste grain and other foods found in the rice fields on the Texas coast in the early 1990s, according to the Houston Chronicle.

With rice production in Texas expanding, the snow geese population also grew, surviving the winter in better condition. But the rice acreage in the state has continued to decrease, as has the habitat for snow geese.

The waterfowl have now taken to wintering in other states—Kansas, Missouri and Nebraska—where increases in grain production have given the geese no reason to migrate any further south.