i have to imagine a field of big old weeds would provide some pretty good habitat. its all in the surrounding habitat too though in winters of a lot of snow and blowing snow. like was mentioned earlier, usually just the upwind side of good blocks of habitat fill in. however, in real extreme winters where there might not be other "habitat" upwind of the large block to catch blowing snow, then its entirely possible for even large blocks to completely blow in. and in years like 97 where we get 100+ inches of snow, everything is going to fill in... not just blow in. regardless, we all know any habitat is better than no habitat.