The babies have fledged! I went out with my dogs this morning and saw Mama Blue. When I approached the birdhouse to untangle some of the streamers on the sparrow spooker, she didn’t even care! She has been dive-bombing me for the past four days if I get within 15 feet of that house. Anyway, that was my first clue. Then, I put out her mealworms and noticed that she was gathering them and taking them to a grove of pine trees that sit about 100 feet from the birdhouse. I took a stroll up there to see if I could spot the babies, and she started chirping loudly and hovering over my head. I guessed that the babies were up there somewhere, so I checked the birdhouse. The nest is clean as a whistle!
Thanks to everyone who offered so much advice and moral support throughout this ordeal. I was so devastated to find the Papa Blue gone, it is such a relief to know that the babies are off and running.