Print PageGlobal environmental change entails multiple processes that are affecting long-term population dynamics. Standardized long-term volunteer monitoring schemes provide a unique basis for the analysis of population global change response. Based on their correlation with population traits, long-term population trends are increasingly being used to draw inference about effects of global change drivers. However, more mechanistic analyses can improve understanding and prediction of global change responses. Here we suggest an approach linking annual growth rates to long-term trends through interactions between environmental variables and population traits. Using this approach we provide a direct evaluation of simultaneous effects of agricultural intensification and climate change on large scale bird population trends. We analyze population trend data from a European wide long-term monitoring scheme. The study includes population trend data for 52 European farmland species spanning 18 European countries over a 20 year period, in total covering 820 populations.
Results/Conclusions
We find that the impact of pre-breeding season winter and spring climate is dependent on migratory strategy. The effects are as expected for proposed climate change mechanisms such as phenological mismatch and competition between strategies driven by winter survival. In contrast, annual growth rates of insectivorous species decrease with increasing cereal yield, though only for short-distance migrants and residents. Our results suggest that the impact of these two global change processes in European birds could be linked to general traits.
