I built a bluebird box earlier this year because the bluebirds kept returning to my yard every year. I assumed they were nesting nearby each season. I was very happy when one pair started investigating my nest box. During mid May they became a little bit tame and not leaving as much. One morning I was sitting on the patio and notice one bluebird taking pine straw to the nest box. Its amazing how much straw they carry and put in one of these nestboxes. To date, they have five eggs and they should hatch around 9 June.