Population trends of European common birds are predicted by characteristics of their climatic niche

Temperate species are projected to experience the greatest temperature increases across a range of modelled climate change scenarios, and climate warming has been linked to geographical range and population changes of individual species at such latitudes. However, beyond the multiple modelling approaches, we lack empirical evidence of contemporary climate change impacts on populations in broad taxonomic groups and at continental scales. Identifying reliable predictors of species resilience or susceptibility to climate warming is of critical importance in assessing potential risks to species, ecosystems and ecosystem services. Here we analysed long-term trends of 110 common breeding birds across Europe (20 countries), to identify climate niche characteristics, adjusted to other environmental and life history traits, that predict large-scale population changes accounting for phylogenetic relatedness among species. Beyond the now well-documented decline of farmland specialists, we found that species with the lowest thermal maxima (as the mean spring and summer temperature of the hottest part of the breeding distribution in Europe) showed the sharpest declines between 1980 and 2005. Thermal maximum predicted the recent trends independently of other potential predictors. This study emphasizes the need to account for both land-use and climate changes to assess the fate of species. Moreover, we highlight that thermal maximum appears as a reliable and simple predictor of the long-term trends of such endothermic species facing climate change.