Hate hot and humid weather when I'm looking for chicks - have to move slowly carrying bucket, blanket (thanks Gail) and there is just no way I can stop until I've exhausted all my options. So, eventually had to give up on my second search of the day after my meeting for work. Made it back to my 'puter and started trolling through the recorded video and almost exactly half-way between the end of my first search and the start of my second, I caught a bird in the nestbox eating "old" food like it hadn't eaten in weeks. Wondered if it could be Nero, then reined myself back and said a) they all eat like that these days, b) hadn't seen any of the chicks in the box at any other time of the day, c) Nero had been 25 stories lower last I saw him and d) usually don't get a clear look at either band when the chicks are in the box because they aren't there very long.
In the end, a) bird was very hungry, b) had a 1 in 3 chance of it being Nero, c) true, but one must always be optimistic, d) bird walked right up to the box cam and hopped up on the ledge showing me its black coloured band. And the answer is, Nero dropped into the nestbox for a late lunch of leftovers.