I also saw a pair of bluebirds checking out the box, so there is apparently a lot of competition for the boxes out there.  I assume someone is maintaining the boxes as they all seem to be in good condition, perhaps one of the staff.  There is no way to tell, of course, what actually happened to the Bewick's Wrens, but there was no sign of them in the area that I could detect. 
David Becher
Saint Louis

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