In the past few weeks both blue tits and tree sparrows have been showing interest in the box. A pair of blue tits has been coming in many times each morning.
The tree sparrows have mostly sat on the roof chirping loudly but one has occasionally dashed in and out, almost too quick for the camera.
The box was put up in 2009 and this is the ninth consecutive year in which it has been occupied. In 2009 a pair of blue tits built a nest but one of them was taken by a sparrowhawk before any eggs were laid. In 2010 a pair of great tits hatched two eggs but neither chick fledged. In 2011-2016 the box was occupied by blue tits which raised 11, 11, 2, 8, 4, and 6 chicks, an average of 7 a year. Early last year I changed the entrance plate to 32mm, hoping to attract tree sparrows, which were in several other boxes, but still the nest was built by blue tits.
Now it looks as though the tree sparrows have adopted what you might call the German Beach Towel Strategy and have moved in and started building. It is said that possession is nine-tenths of the law so they have probably won the battle. It will be interesting to watch them, as they make a change from blue tits and are likely to have two or three broods (the blue tits always have just one). The BTO website says that egg laying starts in mid April and goes on until mid August. The eggs are white with brown blotches with 5 or 6 in a clutch. Incubation takes 12-13 days (slightly quicker than the blue tits) and nestlings fledge after 15-18 days (again slightly quicker). The nest material is noticeably different from that used by blue tits, being grass, leaves and feathers whereas the blue tits mainly bring in moss to begin with.
As I did in the past two years I'll post regular reports on the "Nestbox camera 2017" page (accessible via a separate tab above) with occasional updates here on the main blog.