First nesting pair has disappeared, leaving behind one egg
After installing our first bluebird box, we had our first pair of bluebirds show up in early March. They were very active for a long time, coming and going from the nest box. A few weeks ago, however, I noticed the female seemed to have disappeared. We saw the male, always away from the box, just a couple of additional times, and now he has disappeared as well. I finally got up the courage to peek inside the box. (I had never monitored before.) I saw what appeared to be a well-built nest and one egg left behind. I never saw any fledglings, although I suppose they could have fledged and left without our noticing them.
Any ideas as to what has happened? I'm quite disappointed. What do I do next? Remove the egg, now that weeks have passed since seeing either parent? Remove the nest?
Hoping for a healthy next box again soon! Thanks!