Young sp: The post-juvenile moult is very variable (and have been questioned as it may well be that many birds do not conduct any true moult, only a prolonged completion of the juvenile plumage). Some seem to migrate in unmoulted juvenile plumage while others have moulted parts of body and some, all or no LC and MC. A few birds (10-30% according to Jenni & Winkler [1994], but at Ottenby fewer than that) include innermost GC10, and in rare cases also GC9. TT or RR are not included.
Young WC: The pre-breeding moult includes whole plumage. Variation in wear in spring is likely to be caused by differing (or prolonged) periods of moult during winter.
Adult sp: The post-breeding moult (conducted on breeding grounds or with part of body feathering growing during migration) is partial. The extent seem to rather variable and some only include parts of body, while others (a low portion) may include single RR, single inner GC or single TT.
Adult WC: The pre-breeding moult includes whole plumage. Variation in wear in spring is likely to be caused by differing (or prolonged) periods of moult during winter.