Trends in structure of bird communities in the Czech Republic: from diversity to homogenization?

Biotic homogenization is a process changing functional structure of ecological communities. Bird communities are changing from homogeneous to diversified primarily because specialist species are replaced by non-specialized species (generalists), and in terms of their ecological functions are becoming more similar to each other. Causes can be both in the current climate change and in human-induced land use changes. Using the community specialization index (CSI), I showed that bird communities in the Czech Republic show a trend towards the higher homogenization over the past 20 years. Effect of climate change has been documented by calculation of the community temperature index (CTI), which reflects the relative proportion of species living in lower and higher teperatures. In contrast to CSI, CTI increased over the same time period. Moreover, I focused on the relationship of homogenization with species richness and compared to the results from other countries, it does not change significantly. The observed phenomena were probably caused by a gradual climatic warming in the Czech Republic, accompanied with more frequent occurrence of other climate change symptoms such as severe storms. A second cause underlying the homogenization could be increasing intensity of agricultural production