We built a new house on a lake in NH 1.5 years ago. We put up our bluebird house (on a pole with baffle) last year after seeing our neighbors house/nest. We got our first pair in the second brood, and hatched 5. We cleaned the nest out and made sure the box was clean and ready for this spring. This year we had a nest and counted a total of 6 eggs on May 27th, but the nest seemed extremely tall. We've been checking it once a week since that last egg was laid. The pair was around, but only saw the female on the nest once. It has now been 28 days, so I went to check today figuring the eggs were not viable for some reason as they hadn't hatched when I last looked on Sunday. To my surprise, I saw 1 egg in the nest and no signs of the others anywhere in or below the box. Since the nest seemed even taller, I checked further, and discovered that the nest was actually three nests stacked. The bottom nest had six eggs, the middle nest had six eggs, and the top nest actually has two. Any ideas what is going on, and why they keep creating new nests on top of the old one without any eggs hatching? Anything that we should be doing differently. We now have 12 bluebird eggs that were abandoned.