Nut Cracker?

I am never quite sure when I put out the seeds and nuts for the birds who will end up eating them. At the moment, there is only one, very friendly squirrel, who does not rip up the feeders. S/he did initially but seems to have learned how to eat from them without damage. I wonder what will happen in spring when s/he has a family? I can knock on the window but it won't move- the branch is literally 6 inches from the glass.