To my astonishment, the situation changed dramatically yesterday afternoon as a pair of Eurasian Tree Sparrows entered the large nesting box and starting adding nesting material to the already started Great Tit nest.
At around 14:00 the Great Tit female entered the nest whilst a Sparrow was also inside. A fight ensued which was quickly became a fight between all 4 birds. The male Great Tit entered the nest and also attacked the Sparrow.
After a tumoltous fight, the Tits left the nest. A few minutes later, the Tits again entered the nest and again a fight ensued. Again, the Great Tits left the nest.
After a short pause, the Sparrows started, or rather continues building. It thus apeared that the Sparrows had successfully defeated the Great Tits.
Later that evening, I found out that the Sparrows had started building a nest in the second, smaller nesting box. for some reason, the then decided to continue building in the larger box during the noon hours, during which the Great Tit female paused from nest building.
This morning, the fight continued. The Great Tit female entered the nest various times and fixed it without carrying further material inside the nest. It thus appeared that the Great Tits had not given up on the nest.
With both bird pairs perching in the tree next to the box, several disputes were triggered between the two bird pairs. The most interesting aspects of the disputes were that the Sparrows were more united than the Great Tits where the female performed most of the aggressive stances.
The Sparrows entered the box repeatedly whilst the Great Tits were still in the tree and placed themselves such as to block the entrance of the box. Indeed it could have been interpreted as an attempt of the two Sparrows to block the entrance of the box and thus prevent the Tits from entering.
The disputes continued throughtout the morning and into the early afternoon. After that I no longer observed the Great Tits in the tree or in the vicinity of the large nesting box. In the morning, they had briefly examined the smaller box which also triggered a dispute between the two bird species.
I wonder whether the Sparrows have now taken the larger nesting box and will allow other birds to nest in the smaller box or whether their territory extends to include the smaller nesting box. I also wonder whether the Great Tits will again show themselves tomorrow morning, or whether they have moved on to another nesting location.
The female Great Tit had begung building the nest on the 31. of March. What I also noticed was that whilst only the female Great Tit is responsible for nest building, it appears that both Sparrows are involved in nest building.
I wonder, I wonder....