|Photo by mjp*|
If you followed her comment back to her blog, you already know how she solved this mystery. DKM and Moe took the abandoned chickadee nest out of the box, and found it buzzing. They originally thought they'd saved a lost bumblebee, but eventually realized they'd uncovered her nest.
Really, you gotta check out the pictures and story over at http://backyardspectator.blogspot.com/2012/04/bumbling-surprise-tale-of-woe.html
Honey pots and everything!