For the past two weeks or so, I had been checking my nestboxes periodically--but mostly just their favorite and the new one that I saw a pair checking out. On occasion, I would look in two others. It seems to me, I only looked at the one in the far corner once (the path there had become overgrown last year).
Today, I checked it out, and noticed what I thought was an old nest from last year that I forgot to clean out. Looking inside and seeing some eggs still had me thinking that it was an unsuccessful clutch from last year, but, when I put my phone in and took pictures, I realized the eggs were blue...and newly laid--the bluebirds are back! :)
Seeing no nest-building over the past two weeks had me prepared for my first year without bluebirds. I'm happy that does not seem to be the case.