This is not a Fox Squirrel. It is another kind. Some people call it the piney squirrel. It is actually the Red Squirrel. We have seen photos of these squirrels elsewhere and those populations of Red Squirrels look much more red all over. This one is adding material to its nest in Spring. Usually we see them add material in Fall. Perhaps the baby squirrels are making a mess so this adult had to take out some material from the nest and replace it?