Eighteen hand-raised whitethroats (Sylvia communis) from the Tien Shan (10 S. c. rubicola) and the Caucasus (8 S. c. icterops) were kept in experimental conditions for 2 years and 7 months, including 2 years and 3 months under constant photoperiodic conditions (light-dark ratio 12:12 hours). In contrast to whitethroats from the western population (S. c. communis) previously studied, these birds exhibited distinct circannual rhythmicity, i.e. endogenous annual rhythms of three parameters: molting, seasonal changes in body mass, and seasonal migratory activity. The periods of these rhytms clearly deviated from the calendar year and averaged under constant photoperiodic conditions 383 and 356 days in the birds from the Tien Shan and the Caucasus, respectively. The negative results of the previous investigations might be explained by different origin of the birds, their belonging to other populations or by their keeping in other conditions.