I was hoping to go into this further following Margaret’s excellent photo of a ‘green’ bird in very fresh plumage - and Richard’s comment on it. However the basic information is just not there. HANZAB contains a lot of material in the form of records of various observers, but this is not analysed in a helpful way, and some records are suggested to be unreliable by reason of wrong ageings. A more serious issue is suggested characters that might be attributable not to gender or age but to worn or very fresh plumage. The bottom line seems to be the opening sentence under “Second to fifth immature males” viz. “Very similar to adult female and some birds (possibly second immatures) indistinguishable from adult female on plumage characteristics”.
There is also a need for consistent terminology. Speaking of the bill colour I referred to ‘year x’ birds. HANZAB uses a different approach, as given in the first column of the below table (from Vol 1 Part A).
My attempt to assign a calendar year for discussion purposes is represented by the red annotations alongside the HANZAB terminology. This may be unwise as moults may not coincide with years. Birdbanders have developed their own terminology for calendar years and if HANZAB is to be the starting point I suppose we should follow that method of talking about generations of plumage.
Meanwhile I’ll just continue to collect interesting examples of plumage variations when I find them.
