There are tree sparrows in several other boxes and in holes in trees in my patch of woodland and some of those have already fledged their first brood. This was a youngster I photographed this morning that is already old enough to feed itself.
The BTO website says the tree sparrow clutch size is 5-6 eggs and the median first clutch laying date is 17 May so perhaps this pair is not so late. I expect there will be a few more eggs this week. Incubation is 12-13 days and fledging is 15-18 days after that so we're looking at the second half of June. There may well be a second brood to follow. Lets hope so and that we still have some sort of view into the nest. Regular updates will be on the "Nestbox camera 2017" page (accessed via the tab above). I'll also post any major developments, such as hatching, fledging, etc on this main blog.