Thousands of snow geese fly over Mud Lake on the Sand Lake National Wildlife Refuge in Columbia, S.D., Friday, March 12, 2004. (AP Photo/Aberdeen American News, Dawn Dietrich)

Thousands of snow geese fly over Mud Lake on the Sand Lake National Wildlife Refuge in Columbia, S.D., Friday, March 12, 2004. (AP Photo/Aberdeen American News, Dawn Dietrich)