Last night as it was getting dusky, I was shutting the garage when I saw a small bird fluttering about near my flank wall at loft level and then seemingly fly straight into it and disappear! On closer inspection, it had gone into a 1” hole left from a removed a tank overflow pipe. I’m going to have to bring my borescope home next week and get up a ladder and have a look inside the cavity - it is cavity insulated. What sort of bird nests this time of year?