AGE – BEST CRITERIA:
Moult contrast is always present in the wing of 1cy, 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 and freshly moulted plumage.
1cy:
- Most birds include 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), moult 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.
2cy+:
- Uniform plumage lacking any moult contrast.
- PC denser and with a slightly brighter blue gloss.
- Iris usually slightly warmer greyish-brown.