Abstract
Human‐induced changes in the climate and environment that occur at an unprecedented speed are challenging the existence of migratory species. Faced with these new challenges, species with diverse and flexible migratory behaviors may suffer less from population decline, as they may be better at responding to these changes by altering their migratory behavior. At the individual level, variations in migratory behavior may lead to differences in fitness and subsequently influence the population's demographic dynamics. Using lifetime GPS bio‐logging data from 169 white storks (Ciconia ciconia), we explore whether the recently shortened migration distance of storks affects their survival during different stages of their juvenile life. We also explore how other variations in migratory decisions (i.e., time, destination), movement activity (measured using overall body dynamic acceleration), and early life conditions influence juvenile survival. We observed that their first autumn migration was the riskiest period for juvenile white storks. Individuals that migrated shorter distances and fledged earlier experienced lower mortality risks. In addition, higher movement activity and overwintering “closer‐to‐home” (with 84.21% of the tracked individuals stayed Europe or North Africa) were associated with higher survival. Our study shows how avian migrants can change life history decisions over only a few decades, and thus it helps us to understand and predict how migrants respond to the rapidly changing world.
Highlights
| INTRODUCTIONIf an individual's behavioral traits or its decisions during ontogeny allow us to explain patterns of longevity, we will gain insights into basic life history evolution and understand how migrants respond to the changing world
Migration is a ubiquitous phenomenon that has evolved as an ad‐ aptation to seasonally changing environments (Newton, 2008)
We found that survival during migration was influenced by daily movement activities (ODBA), daily migration distance, fledging date, and the interaction between daily distance and fledging date (Appendix S2: Table S3, df = 8, R2 = 0.453, log‐ratio test p = 0.000)
Summary
If an individual's behavioral traits or its decisions during ontogeny allow us to explain patterns of longevity, we will gain insights into basic life history evolution and understand how migrants respond to the changing world. We hypothesize that these current changes in the white stork's migratory behavior will be reflected in their overall fitness (i.e., individuals with shorter mi‐ gratory distance have higher survival), and thereby influence the entire population's demography. Like in many long‐lived birds, the first year of life is the most challenging period for a stork (Rotics et al, 2016; Sergio et al, 2011) Due to this high mortality, we expect a strong selective pressure on white stork juveniles with differing traits. We used the lifetime tracks of 169 white stork juveniles to link migratory decisions (i.e., time, distance, and destination), move‐ ment activity, and individual traits to their subsequent survival probabilities
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