Yesterday, Friday the 12th, the Eurasian Tree Sparrow made a significant number of visits in the morning between 8 and 9 am, each time carrying twigs and such to the nest. Between 9 and 10 am, something odd happened, the bird flew into the nesting box, quickly landed and started singing incessantly. It was not its usual low frequency chirp with an inquisitive undertone...you can judge for yourself from the video below. From the flickering of the light from the entrance hole, it is clear that after some seconds of incessant chirping, another bird was perched at the outside of the nesting box and was looking inside. This second bird then leave and the sparrow in the box calms down. Its chirping slows and becomes inquisitive, or rather calling, again....well puzzling at any rate.
I wonder if one sparrow having done some work on the nest was attracting the attention of a potential partner to the nest or if the wild chirping can again be attributed to territorial disputes.
According to wikipedia, and I quote here: "Pairs may breed in isolation or in loose colonies, and will readily use nest boxes. In a Spanish study, boxes made from a mixture of wood and concrete (woodcrete) had a much higher occupancy rate than wooden boxes (76.5% versus 33.5%), and birds nesting in woodcrete sites had earlier clutches, a shorter incubation period and more breeding attempts per season. Clutch size and chick condition did not differ between nest box types, but reproductive success was higher in woodcrete, perhaps because the synthetic nests were 1.5 °C warmer than their wooden counterparts.
The male calls from near the nest site in spring to proclaim ownership and attract a mate. He may also carry nest material into the nest hole. The display and nest building is repeated in autumn. The preferred locations for the autumn display are old Eurasian Tree Sparrow nests, particularly those where nestlings had hatched. Empty nest boxes, and sites used by House Sparrows or other hole nesting birds, such as tits, Pied Flycatchers or Common Redstarts, are rarely used for the autumn display." (http://en.wikipedia.org/wiki/Eurasian_Tree_Sparrow)
Today, I noticed a Great Tit inspecting the nesting box (no bird species other than the sparrow visited the nesting box for 4 days). It was chirping wildly on the wooden fence on which the box hangs and was fluttering around as if on display.
I guess nothing is certain yet as to which species has claimed the nesting box its nesting ground.