B6) Multi-scale assessment of bird-forest relationships
Ilse Storch & Marco Basile
University of Freiburg, Faculty of Environment & Natural Resources, Institute of Forest Sciences, Chair of Wildlife Ecology and Management
Birds are commonly-used indicators of biodiversity: they are popular, well studied, and easy to survey. Old forest specialists are of particular conservation concern, and are believed to be negatively affected by forestry. Studies of local bird species richness in managed versus natural forests, however, have reported ambiguous results. Because of their mobility, bird communities are likely shaped not only by local forest structure, but also by the surrounding landscape(1). For old forest species such as three-toed woodpecker Picoides tridactylus and capercaillie Tetrao urogallus, abundance correlates with stand structure; yet, stand structure is an insufficient predictor of species occurrence(2) and hence, of bird species richness.
Study questions and hypotheses
B6 addresses the overall hypothesis that the effects of stand-scale retention measures for biodiversity on forest bird communities are moderated by the surrounding landscape(1, 3).
In particular, we expect that
- Occurrence, abundance and richness of bird species at the scale of forest stands (plots) are explained by local forest structure and by the surrounding landscape
- Diversity of species and functional guilds will increase with heterogeneity at both the forest mosaic and landscape scale.
- The relative abundance and diversity of forest-specialists will increase with the abundance of old forest (habitat trees) and dead wood in the surroundings.
- Although stand-scale structural diversity will correlate with overall bird species richness, occurrence of some species, such as the threatened capercaillie, will not be favoured by structural retention measures.
- There is significant inter-annual variation in the abundance and richness of bird species independent of stand and landscape scale forest structure.
Approach and methods
B6 assesses the structural correlates of avian biodiversity at multiple spatial scales by relating plot-scale presence (passerines, woodpeckers, and capercaillie) and species richness (overall, functional groups, red-list) of birds to the abundance, heterogeneity and spatial distribution of structural elements (old trees, dead wood, open canopy) at plot, stand mosaic, and landscape scales.
B6 annually collects data on bird species presence using repeated point-stop counts in spring (passerines) and surveys of indirect sign (woodpeckers, capercaillie) in summer in all 135 ConFoBi study plots and their surroundings. Data is analysed using multivariate modelling approaches. Resulting models of multi-scale bird-forest relationships are also validated using existing independent data sets from the Alps (Bavarian Alps: capercaillie; own data IS, Austrian Alps: capercaillie, woodpeckers; own data IS; Swiss Alps: forest birds; own data VB). Finally, quantitative threshold values for integrative forest management are derived.
B6 provides bird-count data for all 135 ConFoBi plots to the ConFoBi data pool. B6 advises C1, which models economic costs of management strategies for threatened species, on the habitat requirements of the threatened capercaillie. B6 uses structural data of A1 and A2 and relates the fruit-feeding bird community to the fruit removal data of B3. B6 aims to provide forest managers with quantitative threshold values for the abundance and configuration of stand-scale and landscape-scale structural habitat elements (i.e., old trees, dead wood, open canopy, etc.) in favour of forest bird species and communities.
- Paillet et al. 2009. Biodiversity Differences between managed and unmanaged forests: meta-analysis of species richness in Europe. Conservation Biology 24: 101–112
- Graf et al. 2005. The importance of spatial scale in habitat models: capercaillie in the Swiss Alps. LandscapeEcology 20: 703-717.
- Tscharntke et al. 2012. Landscape moderation of biodiversity patterns and processes – eight hypotheses.Biol Reviews 87:661-685.