The box I put up only last year was nested in by blue tits maybe a month or so after that which was great news for me, and I was fortunate enough to observe the parents flying in and out, firstly with nesting materials, then with all sorts of insects. You can read about my observations of the blue tit family, as well as the nesting nuthatches in the same tree, here and here.
This was my first time both seeing a nest up close and clearing it from a box so it was brilliant experience to have. My initial impression was of just how clean the nest was. I was being wary as I expected to see mites and fleas and for it to be quite unpleasant, particularly as it had been sitting in the box all through the damp, winter months. The reality was quite the opposite of my expectations; there was not one single mite, tick, flea or any other insect (apart from one tiny and slightly disgruntled spider) to be found. It had no smell, no mould and no pieces of eggshell. I knew the parents were frequently removing the faecal sacs as I had observed them doing it. It just goes to show what a fantastic job they did of maintaining a clean nest.
I wanted to get an idea of what materials they had used to form the nest, so I prised sections of it apart and had a good look through, without getting my face too close, to avoid breathing in anything harmful. The primary material was moss which had been used in great volume, creating a very densely-woven framework. There was definitely some solidity despite it being a soft structure. Interspersed between the moss were a variety of other components; leaves, straw, bits of animal hair (likely to be horse and cat since I put clumps of both out last year for them), and pieces of thread and feathers, including pheasant. There were also quite a lot ivy berries, some in big clumps at the bottom of the nest box.
You can see a piece of thread clearly in the top left section, below the leaf.
A few materials, L-R: pheasant feather, moss, ivy berries, leaf.
Today, after clearing out the box yesterday afternoon, I observed a pair of great tits flitting around the branches surrounding the box site. One of them flew into the box and remained for some time while the second spent some time perching on the opening then flying to a nearby branch and back again. I didn't see the first bird exit the box while I was watching but it gave me real hope that, not only might the box be utilised for a second year, but it might be a different species. If they do choose to build a nest and lay eggs, it will be really interesting to see how the nest constructions differ, if at all.
I have registered my nest box with the BTO Nest Box Challenge, which is a survey run to monitor nest sites all over the country. I am hoping that our nuthatches might nest once again in the knot hole a few meters above this box so I will have more than one nest to record observations from.