handrew

At 16.30 today I had 3 WBSEs circling over the house. Two were adults and regulars. This bird is presumably a sub-adult - can someone confirm / correct please - and not a regular. I have not seen this plumage here in recent memory.

wgeoff

Immature - see page 122 of Brazil - Birds of East Asia

handrew

Geoff, I looked at Brazil's book as well as Raptors of the World and finally this morning OBC Images. Immature always strikes me as an odd description as any bird that is not mature is by definition immature. WBSE seems to be mature in 5 years. I think after looking at various sources that sub-adult is probably a better description. I was torn between photographing this and the Blue Rock Thrush in the garden!

wgeoff

Yes I agree. sub-adult is better - I guess it's fourth year. But this is a plumage I don't recollect having seen before - I was quite surprised to find it displayed in Brazil.

I don't know if there is a generally accepted technical definition of juvenile, immature and sub-adult.