About 3:25 PM, curiosity finally prompted me to set up the ladder and look into the bird house. I hadn’t seen any activity; Mama and Papa Bluebird were nowhere in sight. My worst fears were realized: The nest is empty!! ~~ With 20/20 hindsight, I should have installed a baffle on that pole. Although I haven’t seen a squirrel, or raccoon, on that pole, I should have considered the possibility that a “critter” might rob the nest.
Postscript, Friday, 07/27/2012, 8:30 AM: Occasionally, the Bluebirds return for mealworms. (Click on the picture to enlarge it.)
Postscript, Saturday, 07/28/2012, 9:30 AM: Ditto, above.