AGE – BEST CRITERIA:
Most individuals are redily aged according to the below criteria, but a few may be somewhat more problematic:
- A few individuals include GC10 (and occasionally GC9-7) in the post-juvenile moult. Moulted feathers have better structure, slightly darker centre and brighter greener edges than the juvenile ones, but may still be difficult to detect. Check for moult contrasts also in RR and TT (may also occur in LC or MC, but are generally diffucult to see).
- SS are fully grown before onset of autumn migration.
- Yellow on throat, breast and belly are rather evenly distributed and generally reaches between the legs (note however, that northern acredula are less yellow than nominate).
- Iris colour cold and dark grey.
- Juvenile RR, PP and SS are generally more narrow, slightly more pointed and show a less good feather quality (less dense, less gloss and with a weak brownish ground colour).
- PC and TT slightly paler, less dense and increasingly more worn during autumn.
- Whole plumage fresh, lacking moult contrasts (but note that a few may retain/’forget’ a single inner SS or LC).
- Most individuals start autumn migration with innermost S6 still growing and with feather sheath still present during late summer/early autumn.
- Yellow on throat and breast often gives the impression of being concentrated in lines/bands, and belly (incl. the area between the legs) are generally more whitish.
- Colour of iris warmer dark greyish-brown.
- PC are more dense and often with slightly greyish edges.
- Alula feathers show glossy dark centra with fresh greyish tips/edges.
- RR, PP and SS are generally broader and in better condition (denser, darker more glossy).
- PC and TT slightly darker, denser and in slightly better condition.