AGE – BEST CRITERIA:
Autumn criterias are still applicable, though the still juvenile feathers in 2cy are more affected to wear during the winter than adult. Moult contrast is always present in the wing of 2cy, in the vast majority between post-juvenile GC and juvenile PC. Moult contrast may also be present in RR, alula and TT. Adult birds show a uniform plumage.
2cy:
- Most birds included all GC in the post-juvenile moult. The fresh and dense GC with rather bright blue outer vanes shows a contrast to the less dense and less brightly coloured juvenile PC. This contrast may be easily detected, but a few may need a more careful study. In some birds (14% at Ottenby) 1-5 outermost GC may be unmoulted juvenile (less dense and less bright blue), and then show a more easily seen contrast to inner post-juvenile GC.
- A moult contrast is sometimes seen in the alula, often with CC and the innermost alula moulted post-juvenile contrasting to outer 1-2 juvenile alula. Post-juvenile alula are more dense and bright blue (like the post-juvenile GC) than juveniles ones.
- Most birds, c. 70% according to Jenni & Winkler (1994), moulted all TT. Among the rest, the vast majority shows one (the longest) unmoulted juvenile T, while 2-3 retained juvenile TT are rather rare.
- C. 70% (according to Jenni & Winkler [1994]) moult R1, and 5% include several RR. Only c. 25% moult no RR at all.
- Iris is rather dark olive-grey.
3cy+:
- Uniform plumage lacking any moult contrast.
- PC denser and with a slightly brighter blue gloss.
- Iris usually slightly warmer greyish-brown.