Swiss bird communities in constant change
The massive changes in the landscape on the one hand and the progress in species conservation on the other have also affected breeding birds. Wetlands and their inhabitants have suffered huge losses, the species composition in farmland has changed significantly, and birds that were once persecuted have recolonised Switzerland or expanded their range.
In the past 200 years, the Swiss landscape has changed faster than ever before. Between 1850 and 2010, more than 90 % of wetlands were lost. Farmland has been transformed due to land consolidation, fertilisation and mechanisation. Population growth and infrastructure development have turned rural areas into urban agglomerations. Nutrient input has fertilised naturally nutrient-poor soils and led to the eutrophication of waterbodies. On the other hand, hunting bans now protect many species after centuries of persecution.
A look at the impact of these changes on bird communities reveals a mixed picture: between 1900 and 2010, 25 new species established themselves as breeding birds in Switzerland (including four non-native species), while nine disappeared. New additions like the Rook and the Great Cormorant have contributed to this positive overall balance; as colony breeders, they are particularly vulnerable to persecution and have directly benefited from improved international protection. On the other hand, some species have been able to sustain small local populations despite steep declines, often thanks to conservation measures (e.g. Little Owl). These declines therefore do not affect the overall Swiss record, and so a simple sum of losses and gains only partially reflects the important changes happening in the avifauna. Some wetland species have suffered particularly drastic declines. Eurasian Curlew and Common Redshank, for example, no longer breed in Switzerland. But other species too, such as Common Cuckoo, Spotted Crake or Common Sandpiper, have dwindled in number due to the massive loss of habitat. Moreover, once common farmland species such as Woodchat Shrike, Common Redstart or Tree Pipit have now vanished completely or at least sharply decreased. Suitable breeding conditions for these species have become hard to find. Insect numbers have taken a plunge, depriving the birds of an essential food source.
On the other hand, the past 30 years especially have seen an increase in species like Red Kite or Carrion Crow, which forage in farmland but raise their young elsewhere. This trend mostly concerns large species that can cover long distances while foraging and are therefore able to benefit from the food available in farmland. The increase of crows and raptors in turn leads to greater predation pressure on ground-breeding birds.
Humans are transforming their surroundings with far-reaching effects and at incredible speed. As a result, the composition of bird communities has been in constant flux throughout the past century. The avifauna as a whole is flexible enough to cope with an ever-changing environment. Species with special requirements, however, are often unable to adapt and eventually disappear as breeding birds.
Hallmann, C. A., R. P. B. Foppen, C. van Turnhout, H. de Kroon & E. Jongejans (2014): Declines in insectivorous birds are associated with high neonicotinoid concentrations. Nature 511: 341–343.
Hallmann, C. A., M. Sorg, E. Jongejans, H. Siepel, N. Hofland, H. Schwan, W. Stenmans, A. Müller, H. Sumser, T. Hörren, D. Goulson & H. de Kroon (2017): More than 75 percent decline over 27 years in total flying insect biomass in protected areas. PLoS One 12: e0185809.
Stuber, M. & M. Bürgi (2018): Vom «eroberten Land» zum Renaturierungsprojekt. Geschichte der Feuchtgebiete in der Schweiz seit 1700. Bristol-Schriftenreihe. Bristol-Stiftung, Zürich, und Haupt, Bern.