Effects of climate change on birds in Switzerland

Climate and available habitats are the most important factors determining the distribution and abundance of birds in Switzerland. We are already starting to see initial effects of climate change on various species. For example, short-distance migrants often return early from their wintering grounds in spring, and mountain dwellers are retreating to higher altitudes. For some species, forecasts predict major changes in the decades to come. Detecting changes in distribution and population size early is important in order to recognize when a species is at risk. Several of the Ornithological Institute’s projects are devoted to this issue.

Aims

•  identifying species that are affected by climate change and documenting trends in altitude distribution, range and population size
•  studying the occurrence of species throughout the annual cycle (phenology)
•  researching the ecology of national priority species

Approach

The effect of climate change on birds is an extremely broad topic, and its study requires both wide-ranging analyses that encompass all species, and detailed ecological studies of individual species.

Effects of climate change on breeding birds

The Swiss Ornithological Institute calculates a climate change vulnerability index for all species of breeding birds. This index, which is updated annually, informs us about the actual changes in population sizes. Mountain dwellers are presumably more sensitive to rising temperatures than lowland species, and respond by retreating to higher altitudes in the Alps. Conversely, species that thrive in warm climates are predicted to increase. Using data from the monitoring and atlas projects, we investigate whether such changes are already underway.

Ecology of individual species

Ecological studies of individual species are a necessary part of identifying and understanding climate-induced mechanisms. The focus here is on alpine species such as Rock Ptarmigan and White-winged Snowfinch. Due to its topography, Switzerland is home to a large percentage of the European populations of these species, and has a long-term responsibility for their survival.

Phenology

Migrants benefit from returning as early as possible to their breeding grounds in spring in order to secure the best habitats. Long-term data series allow us to identify climate-induced changes in arrival dates. Based on these findings, we are developing a phenology index for migrants.

Significance

Climate change has been identified as one of the main threats to biodiversity in the coming decades. In the Alps especially, its effects are already visible and will only intensify in the future. Switzerland has a responsibility of international scope to ensure the survival of many alpine species. In addition, the situation in Switzerland is also being modified by new species coming here from other regions and spreading. Therefore, studies of Swiss breeding birds have a high priority.

Results

Data from the programme "Monitoring common breeding birds" allow us to show that within a decade, more than a third of all species display an upward trend in altitude distribution. The results of the breeding bird atlas 2013–2016 will allow a more in-depth analysis of the changes in altitude distribution as compared to 1993–1996.

The Rock Ptarmigan is moving upwards at a rate of 100 m per decade. Due to topography, the available habitat decreases with altitude. We have already been able to show that the species is declining by varying degrees in different areas. On average in Switzerland, the rate of decline is -13 % in the course of 18 years.

Based on the records of opportunistic observations, we investigated whether the main song period in spring has shifted in the last ten to 15 years. Some species showed no change, whereas others have advanced the peak of their song period by more than ten days in ten years.

Project management

Thomas Sattler, Hans Schmid, Lukas Jenni

Partners

Dr Boris Schröder, Technische Universität Braunschweig, Germany
Dr Niklaus Zimmermann, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Birmensdorf, Switzerland
Dr Janine Bolliger, Swiss Federal Institute for Forest, Snow and Landscape Research, Birmensdorf, Switzerland
Dr Richard Gregory, Dr Ruud Foppen, European Bird Census Council (EBCC)
Federal Office for the Environment FOEN

Publications