I use recordings on a random playlist (from an old android phone I have) a lot for all kinds of birds and it absolutely helps attract bluebirds. I keep other birds on it like phoebes and kingbirds that I think make bluebirds feel like it is a good place to check out and not be threatened. I feel like I hear the short one note call by bluebirds more so I play that a lot. I do wonder if it scares them away if playing continuously because i have attracted them for sure but they seem to move on from fleeting visits. I get tree swallows easily every year but bluebirds are tough to keep here. I also tried the mealworms but the starlings find them and clean me out. I do have a amall cage feeder that keeps them out for the most part but I only get Carolina wrens going in there. I plab to try in the fall again. My brother has a platform feeder that he has tons of bluebird activity on but he has less of a staring problem. Agree with van ert being essential. If anything I am really good at controlling HOSP. And it is making a significant impact finally. I use the ground cage trap in the off season and that is critical for trapping the influx of hosp flocks that come through.