Swiss Bird Index SBI®

Birds are considered reliable indicators for changes in the environment and its habitats. An individual species’ increase or decline, however, is dependent on multiple factors. That makes a general assessment of the changes occurring in its habitat difficult. Indices based on the trends of several species, on the other hand, make such assessments possible. The Swiss Bird Index SBI®, updated annually, contains a set of such indicators. It therefore provides an important basis for authorities, environmental organisations and nature conservation groups.

Results

The breeding population indices for individual species are available in our online database Birds of Switzerland as well as in this overview.

The Swiss Bird Index SBI consists of an overall index for the calculation of which all regular breeding bird species in Switzerland are taken into account. In addition, various sub-indices are calculated based on a selection of species. For this purpose, species are selected according to a special interest list (Red List, Swiss Species Recovery Programme, International Responsibility, Environmental Objectives for Agriculture), habitats (forest, wetlands, alpine habitats, settlements), and the SBI® Climate Change (species that are predicted to increase or decline with climate change). A complete overview of the SBI indices can be found here. Selected results of the SBI are discussed in more detail in the annual report on the state of birds in Switzerland. All indices are updated annually. 

The overall index and several sub-indices are included in the statistics of the Federal Offices for the Environment, Statistics and Agriculture. Furthermore, the species-specific breeding population indices are taken into account in the calculation of the European species trends and habitat indicators. 

 

 

Methodology

The calculation of the Swiss Bird Index SBI is based on the species-specific population development of regular breeding birds. For common breeding birds, the annual values are based on data from the programme “Monitoring Häufige Brutvögel” (MHB). For species that are rare throughout the country, the estimated proportion of occupied kilometre squares is used as an indicator of the population development. These estimates are based on the analysis of occasional observations submitted by the ornithological station's volunteers. In the case of species that are generally rare throughout Switzerland, but locally more abundant, count data from MHB and the Swiss Biodiversity Monitoring are considered in addition to the occasional observations. In both cases, the increase in observation effort is taken into account in the analyses. Finally, the population indices of very rare, particularly well-monitored species are based on national or regional population figures.

For the SBI, native species that have met the criterion as regular breeding species at least once since 1990 (breeding in 9 out of 10 consecutive years) are considered. Only three of these species (Collared Flycatcher, Italian Sparrow & White-backed Woodpecker) cannot be taken into account due to a lack of data for estimating population trends. The resulting SBI-Indices are the outcome of a negative binomial model with species-specific annual populations as input data (Korner et al. 2022). In addition, pie charts are used to show how many species have appeared or disappeared since 1990, how many have clearly increased or decreased, and how many species did not show a clear trend. The procedure for classification into increasing or decreasing species is as follows: The previously calculated species-specific breeding populations indices (including associated standard errors) are log-transformed and then analysed using a linear model with year as the explanatory variable. The calculation method is based on the principle of meta-analyses, where the point estimates (including their uncertainty) resulting from a previous analysis, are evaluated in a second analysis. Such meta-analyses occur in various applications, see e.g. Section 11.6.4. in the 2016 book Applied hierarchical modeling in Ecology by Kéry & Royle. A species is classified as increasing or decreasing, if the population trend resulting from the meta-analysis is estimated to be clearly different from 0 (slope of 0 is not included in the 95% confidence interval). 

 

Project management

Nicolas Strebel, Sylvain Antoniazza

Partners

European Bird Census Council
Biodiversity Monitoring Switzerland
Swiss Biodiversity Forum

Publications