SEASONAL AND DIURNAL VARIATION OF WEIGHT IN FOUR PASSERIFORMES IN AUTUMN AND WINTER

IOALE' P. & Benvenuti S.



Abstract:

During four years of ringing activity, we collected data on seasonaI (autumn and winter) and diurnal variatiornin body weight in four species of passerine birds (Robin Erithacus rubecula - Wren Troglodytes troglodytes - Dunnock Prunella modularis - Blackcap Sylvia atricapilla). Among the populations of the first three species, resident from October to March, we recorded a continuous increase in body weight, even when the environrnental temperature was rising in Febraury and March. This pattern of weight variation i s different from that observed in t rans+Se haran migrating pas se+ rines, and in cold climates wintering birds. We also recordea a weight increase during the day, due in part to the storage of lipids utilized during the nightime resto