Probably a Dud

The Colonial Williamsburg "bird bottle" is stuffed with nesting material.  Wrens have used it before (summer 2011.)  But are they actually using it?  Maybe not.  I have kept my eye on the bottle for two weeks and have seen absolutely no activity whatsoever.  I suspect we may have a dud here.  If true, the wrens either aborted their attempt: spooked by something.  Or, this was one of several demonstration models rejected by the prospective female tenant.  I may have to go up and clean the thing out if it is to be used this summer.  But patience is called for.  Maybe, just maybe something interesting will happen!