After Posting Bluebird Update April 26, 2012 I went out to check the Butterfly House nest box. The parent bluebirds were not brining food into the box but were apparently waiting out the nestlings.
I’ve seen them do this many times, the parent usually with a juicy caterpillar or other food item in its bill, sitting outside the box some distance away coaxing the nestlings out.
In this case the parents were some 20 and 30 feet away on a fence and lamp post watching to see if the youngsters would exit the box. I was called away on other duties, but a check later in the day revealed an empty nest box.