COS 136-1 - The role of seasonal migration in spatial population synchrony

Background/Question/Methods

The extent to which populations of the same species co-fluctuate in abundance (i.e., population synchrony) is key for predicting metapopulation persistence. A high degree of spatial population synchrony can inhibit metapopulation recovery from synchronized low abundance periods, with more synchronized populations more likely to go extinct, which has important implications for both local and metapopulation management strategies. Nearby populations tend to be the most synchronized because of spatial autocorrelation in the environment. For migratory species, this relationship is more complex, because the environmental covariance among individuals and populations may change across seasons. To understand the role of seasonal migration in spatial population synchrony, we simulated expected spatial scaling of synchrony based on population-dynamic modelling across combinations of migration strategies and life history characteristics such as longevity and average clutch size. We then used abundance estimates from long-term avian monitoring programs in Norway, Sweden, Switzerland, and the United Kingdom to empirically explore the simulated relationship and test for differences in the scaling of spatial population synchrony based on life history traits and migratory strategy across multiple avian taxa.

Results/Conclusions

The spatial scaling of synchrony on the breeding grounds was strongly influenced by type of migration and the spatial environmental autocorrelation experienced off the breeding grounds. Importantly, these effects depended on the species’ life history traits, such as generation time. We found further support for these conclusions in a study of common avian species in Norway, Sweden, Switzerland, and the United Kingdom, where we identified differences in the scaling of spatial population synchrony by migration strategy and generation length. These results have implications for our general understanding of how we calculate and assess mechanisms causing spatial population synchrony. These results also aid general understanding of the impacts of environmental change on migratory species, which are particularly vulnerable to climate change and showing severe population declines.