![]() Because the specific needs and conditions at each stage of the annual cycle might differ (e.g., fattening up prior to a migratory trip or finding extra food for raising the offspring), it is expected that animals adapt their behaviour-and the associated energy expenditure-accordingly. These energy-demanding events are scheduled within the annual cycle with as little overlap as possible between them. The main life-history events in birds are breeding, moult, and in migratory species, migration. The annual cycle of many organisms consists of a succession of life-history events separated by time and potentially location and underpinned by ecological and physiological processes. The use of multisensor data loggers to track annual activity provides us with a full annual perspective on variation in activity in long-distance migratory species, an essential approach for understanding possible critical life-history stages and migration ecology. ![]() ConclusionsĪctivity measured during daytime results from a combination of several behaviours, and a high daytime activity during spring migration and the breeding period is possibly reflecting particularly energy-demanding periods in the annual cycle of migratory birds. The birds showed a lower daytime activity on migratory days (days when a migratory flight took place during the succeeding night) than on non-migratory days during both migratory seasons. During migratory periods, both sexes exhibited a higher daytime activity in spring compared to autumn migration, being particularly high in the final migratory leg towards the breeding ground. Daytime activity differed between sexes during the breeding period, when the males showed the highest level in activity. The highest daytime activity levels were observed during the breeding season, while it remained low during autumn migration and the winter period. The birds’ daytime activity varied throughout the annual cycle while night-time activity was almost exclusively restricted to migratory flights. In this study, we analysed the variation in daytime activity along the annual cycle and between migratory and non-migratory days. Accelerometer data was used to identify life-history stages and to estimate levels of activity during various phases of the annual cycle. We used multisensor data loggers to evaluate the patterns of activity throughout the complete annual cycle of a long-distance migratory bird, the red-backed shrike Lanius collurio. ![]() Yet, variation in activity throughout the entire annual cycle has rarely been studied in wild migratory birds. Long-distance migratory birds undergo complex annual cycles during which they must adjust their behaviour according to the needs and conditions encountered throughout the year. ![]()
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