A year or more ago a Blogger read one of my posts on the Bluebird in my yard and recommended that I read a book titled "The Bluebird Effect: Uncommon Bonds with Uncommon Birds." It has artful illustrations and is the story of a woman and her relationship with a bluebird that she saved and released. It is a lovely and gentle read if you have a short booklist and want to add it.
I have a friend that maintains two Bluebird trails (the Eastern Bluebird) and has great success with the boxes she builds and installs along meadows and along woodland edges and near golf courses. She posts their nests and the young who are a blue-gray with gaping mouths on Facebook.
My experience has been that Bluebirds have unique and individual personalities. Years ago when one nested in a box near my rose arbor I used to get all kinds of acrobatic judo attacks with the snapping of wings and angry chirping just a foot from my head. This year I have a Bluebird couple nesting in that same box, but he (female may be on eggs) flees the minute I cross the lawn. He perches on the outer edge of a large tulip across from the driveway and tweets incessantly but melodiously as I weed in that flower bed. He is clearly distressed but not brave enough to dive over my head.
Is he younger and timider? Is he older and wiser? Is it just a less aggressive personality he has? He sure is pretty when he doesn't know I am watching behind a window.