The Tree Swallow pair return to the branch over the pond every day.  When she is in the nestbox, he sits on the branch to keep watch on her and their eggs.  Sometimes she joins him there. They can survey their territory, chase away intruders, and spy food items flying by.  Or, just sit close together.  On occasion, he sings to her.  She has been incubating eggs for 11 days.  They will hatch any day.