Little squirrels!

I first spotted these little tykes the other evening and managed to snap some pictures of them the next morning.  There are, as far as I can tell, four little squirrels living with their mother in a nest inside a branch of a big maple out the back of our house.  Two of them are pictured here, one playing outside, and the other poking its head out of the nest and looking around cautiously.

I don't think that they belong to Myrtle - she doesn't hang around that tree much, and these little guys seem too big to have been born less than a month ago.  I did see what I assume was the mother tending to them and she didn't look very familiar - I think she visits our deck for food, but she's not the character that Myrtle is (but she is raising four pups on her own, so all power to her).