I suspect there is a nest hidden here and will watch it for signs of life over the next few weeks. I do not want to frighten or harrass her so I settled for a picture of the entry and did not climb up to look inside.
What struck me funny is that this is not really a hole in the tree at all. it is actually two trees that have grown together at the base and this is the Y where they split apart, A piece of bark fell and wedged there and needles built up around it creating what appears to be a snug and dry hollow that goes back between the two trees for about 3-4 feet and is closed off on the other end with more bark and needles.
So what do you think? Will I ever see her again? Or was this just an exploration and she will actually nest elsewhere?