On our visit to the wood today we went to investigate the two bird boxes that we had previously installed - one on 'Middle Tree', a 70 years old oak, and one on 'the Faraway Tree', possibly 100+ years old. The boxes were installed back in February and the one on Middle Tree has a hole diameter of 25mm and the one on Faraway Tree has a 35mm hole. The boxes, which we bought from the RSPB, were put on the north side of the tree to provide shade from the summer sunshine (if we get any!!).
I am pleased to say that the box on the Faraway Tree has blue tits in residence. If they succesfully nest then next year I would like to install more boxes and put cameras into one or two of them.