Dear Gary
I personally think the term 'juvenile' is both safe and vague for a bird which has left its nest and is able to do independent feeding/hunting. 'Calender year' is, though coined in terms of human culture, gives us a good idea of the length of time after a bird is born. So if your knowledge that the young WBSE is over 14 months since born (presumbably you've been monitoring this individual since it has fledged somewhere in HK) is perfectly recorded, eRic's brother, who is in Australia, proves to have given us, particularly me, a sound judgement based on moulting pattern of WBSE in general.
I'm well convinced that the WBSE in question is in its 2nd calendar year.
Thank you here for eRic's answer for my 'riddle' and further information, for Gary and Beetle's
help with what can be found in the Society's bulletin.
S L Tai