Generation time and seasonal migration explain variation in spatial population synchrony across European bird species

O_LISpatial population synchrony is common among populations of the same species and is an important predictor of extinction risk. Despite the potential consequences for metapopulation persistence, we still largely lack understanding of what makes one species more likely to be synchronized than another given the same environmental conditions. C_LIO_LIGenerally, environmental conditions on a shared environment or a species sensitivity to the environment can explain the extent of synchrony. Populations that are closer together experience more similar fluctuations in their environments than those populations that are further apart and are therefore more synchronized. The relative importance of environmental and demographic stochasticity for population dynamics is strongly linked to species life history traits, such as pace of life, why may impact population synchrony. For populations that migrate, there may be multiple environmental conditions at different locations driving synchrony. However, the importance of life history and migration strategies in determining patterns of spatial population synchrony have rarely been explored empirically. We therefore hypothesize that generation time, a proxy for pace of life, and migration play an important role in determining spatial population synchrony. C_LIO_LIWe used population abundance data on breeding birds from four countries to investigate patterns of spatial population synchrony in growth rate and abundance. We investigated differences in synchrony across a gradient of generation times in resident, short-distance migrant, and long-distance migrant bird species. C_LIO_LISpecies with shorter generation times were more synchronized than species with longer generation times. Short-distance migrants were more synchronized than long-distance migrants and resident birds. C_LIO_LIOur results provide novel empirical links between spatial population synchrony and species traits known to be of key importance for population dynamics, generation time and migration characteristics. We show how these different mechanisms can be combined to understand species-specific causes of spatial population synchrony. Understanding these specific drivers of spatial population synchrony is important in the face of increasingly severe threats to biodiversity and could be key for successful future conservation outcomes. C_LI