I think A5 nailed it, those corn fields blow full, not clear.  IF there is snow on the the ground that has blown, that snow will be as deep as the top of the corn stocks 6 inches to 2 feet, depending on the corn head and operator.  Beans are cut close to the ground and will catch very little snow, which is much easier for them to dig through.  The cover will catch snow until there in nothing to catch the blowing snow.  About 5 years ago, we had some tough snow conditions, the pheasants works across a half mile bean field that butted up to our CRP and then started across the road into the next bean field before the snow melted back where they could find other food.  They left it looking like a dalmatian, black and white,  as they work further and further across the field.  There were a hundred of them at times.  After that I began leaving a steel drum of shelled corn in the field, just for tough times.  Not unusual, (very common here) to harvest birds, even with no snow, with their crop full of beans.