Forgive me for what is going to seem like a "trollish" question. It's definitely not meant to be!
In our neck of the woods, we have snow cover about 5 months or so out of the year. The only thing still green this time of year are evergreens. Everything else is long dead and buried in snow. So while we are doing our best to make sure our "in house" squirrels are eating their veggies, what are the wilds eating this time of year? They are at my feeder - but that's just the run of the mill bird/squirrel food. Part of my reason for wondering is if this time of year puts wilds at particular risk of MBD. The other part is wishing I could simulate wild diets but I just can't really figure out what they would actually be eating!