I'm not a Bobwhite keeper, but I'd guess it's pretty much like it is with Coturnix and chickens. Make sure they have a place to get out of the snow/cold -- some sort of shelter that they can get into. Bobwhites live in the wild in many places, even Wisconsin (though their range now only includes a portion of the state there.) If they can survive a Wisconsin winter, then they probably don't need a ton of fancy winter care.
My guess would be to make sure they have water that isn't frozen, provide them a dry, sheltered area out of the wind (perhaps line it with something like hay to insulate it - but only if the hay will stay dry!). Someone else will have to answer in regard to any nutritional needs/differences in the winter.