PRIMARY MOLT, BODY-MASS AND MOLT MIGRATION OF LITTLE TERN STERNA-ALBIFRONS IN NE ITALY

Large post-breeding gatherings of Little Terms Sterna albifrons are re gularly observed in the Lagoon of Venice, Italy. Here, during five con secutive trapping seasons, 2956 birds were examined and ringed. Their breeding area, as indicated by 163 direct recoveries (mainly juveniles , ringed as chicks), spans over a broad sector of the Adriatic coasts, with colonies located up to 133 km far. During their stay at the stud y area, adults undergo an almost complete moult. Two partial primary m oult cycles can be observed, the first of them being suspended when 2- 4 outermost long primaries have not yet been shed. Pre-migratory body mass build-up, enough for a flight longer than 1000 km, takes place du ring the very last days before departure to the winter quarters, in mo st cases when the moult has reached a suspended stage. Active primary moult and body mass increase do overlap in late moulting birds (after 27 August), indicating that the two processes are compatible, in case of time shortage. Post-breeding movements to the Lagoon of Venice seem to fit most requisites of moult migration.