The impact of climate change on long‐term population trends of birds in a central European country

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AbstractNumerous studies have shown that climate changes associated with increasing global temperature affect bird species. For instance, long‐distance migrants are not able to respond adequately to rapid advances in spring phenology, and thus their populations decline due to lower breeding performance. Moreover, many species in the Northern Hemisphere have shifted their northern breeding range boundaries further north. However, studies focusing on bird populations at the scale of individual countries, which are responsible for creating environmental policies, are rather scarce. We hypothesized that bird species with different European latitudinal breeding distributions would have different long‐term population trends in the Czech Republic, a small central European country, as a result of range dynamics caused by increasing spring temperature. In accordance with this prediction, the results of an analysis based on large‐scale monitoring data (from 1982 to 2006) showed that species with more northern latitudinal distributions had more negative population trends in the Czech Republic. However, the strength of the relationship depended on the approach used for characterization of the species latitudinal distributions. When a phylogenetic regression was applied, the only significant explanatory variable was the latitudinal distribution expressed in categories defined by species range areas in different latitudinal bands. A more detailed analysis showed that southern and northern species groups have opposite population trajectories: the former increased and the latter declined throughout the study period. The effect of climate change remained significant when habitat association and the migratory strategy of each species were taken into account. However, it is difficult to determine whether climate change or habitat change is the more important driver of long‐term trends in bird populations as the effects of both factors are dependent on interspecific variability in levels of species specialization.