As already mentioned, there are three different bird species that have been visiting the nesting box. Although the Eurasian Tree Sparrow is the only one that is really working on the nest whilst the Blue and Great Tits just hang around, there have already been intense "verbal" disputes. Both the Blue and Great Tits have displayed aggressive behaviour towards other birds wanting to enter the nest, despite their apparent superficial interest in the box.
With the IR B/W camera I have recorded images of both the Blue and Great Tits sitting around in the box calmly and then suddenly becoming very loud and, for a bird that size, aggressive. At first I was not really sure about what was going on, until I realised that the ring of light coming from the entrance hole was flickering, meaning that another bird was perched next to the hole wanting to enter the box.
Yesterday, I managed to get excellent video footage of a Great Tit in the box "bickering" (I will have to read up on birds a bit to get my terms right, I hope you will excuse my "humanisation" of the birds 'til then) with the same flickering and with the chirping of another bird in the background but also quite loud.
I try not to side with any one bird, but I must confess, that I have taken a definite liking for the Eurasian Tree Sparrow, considering the work it has invested so far. I have read that due to the increasing use of land for agricultural purposes, and due to lack of food, Eurasian Tree Sparrows find it difficult to find nesting grounds and that their numbers are falling rapidly. Indeed this species has been added to the IUCN Red List of Threatened Species.
I will be loading a video of yesterday's territorial disputes later today...so stay tuned.