Mysterious Goings-On

We continue to watch the doings at our most popular nest box.  A pair of White Breasted Nuthatches has definitely taken up nesting activity, as they have for three continuous years. But it is unclear they've done much beyond making a nest.  I see both birds engaged in feeding activity.  Are there already hatchlings?  I suppose it is possible if a tad early.  What I can't bring myself to do is get into a position to investigate: I'm happy enough things have advanced as far as they have.  Perhaps we shall know more in a few weeks---or days.