Bewick’s swans in a changing world : Species responses and the need for dynamic nature conservation

Many species are threatened with extinction due to global environmental changes, and their ability to respond to these changes will determine their fate. The Bewick’s swan (Cygnus columbianus bewickii) is an obligate migratory species that migrates between Northwestern Europe and the Arctic Russian tundra. This western population of Bewick’s swans has shown considerable fluctuations over the study period of ~ 50 years. By including population counts and reproductive counts in an integrated population model with mark-resighting data, we were able to show a decreasing trend in apparent breeding success and a simultaneous increase in juvenile survival as demographic drivers of the population numbers. Further analysis of mark-resighting data revealed that the population has significantly shifted its wintering distribution eastwards (i.e. ‘short-stopping’) and shortened the stay in the wintering area (‘short-staying’), which can explain the drastic declines in the western part of the range (Ireland and UK) when compared to the eastern part (mainland Europe). These changes happened in parallel with climate warming in NW Europe. As a result we found that, especially in recent years, some important sites for the swans were not protected by the Natura 2000 legislation of Europe. Reflecting on the status of this Bewick’s swan population as ‘Threatened’ on the European Red List of Birds, and the dynamic response to environmental changes shown by the research in this thesis, it is to be expected that the mismatch between the important sites for the swans and the Natura 2000 protected areas will increase. Our efforts to protect nature, such as Natura 2000, are often fixed in both time and space. This could undermine the effectiveness of conservation efforts. For species such as the Bewick’s swan that show changes over time in their site use and phenology, a more dynamic approach could benefit nature conservation.