Abstrakt
European birds have been significantly affected by dramatic environmental changes during the last decades. The effects of these changes on species richness and distribution in particular countries are still poorly understood because of a lack of high-quality, large-scale data standardized over time.
This is especially true in Central and Eastern Europe. On a model group of birds in the Czech Republic (countrywide atlas mapping data), we examined whether long-term changes of species richness and distribution between 1985-1989 and 2001-2003 differed among groups of species defined by their habitat requirements, type of distribution in Europe, migratory strategy and the degree of national legal protection.
Further, we investigated the effects of colonizers and local extinctions on these changes. Whereas the number of species in the whole country remained the same in both periods (208 species), species composition had changed.
Increasing occupancy (i.e., number of occupied mapping squares) was observed in species of forest and wetland habitats, in short-distance migrants and in non-protected species. Southern species also positively changed their occupancy, but this pattern disappeared after the inclusion of six species dependent on extensively cultivated farmland that went extinct between mappings.
The overall occupancy of all species together showed positive changes after excluding colonizers and extinct species. We suggest that the improvement of environmental conditions after 1990 caused the stability of or increased the distribution of common birds in the Czech Republic, and it was the disappearance of specific farmland practices that might have caused the loss of several species.