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B6) Bird-Forest Relationships

Multi-scale assessment of bird-forest relationships

Ilse Storch
Doctoral researcher: João Manuel Cordeira Vale Pereira (since 2019)

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 comparatively easy to survey. Old-growth forest stages, and bird species associated with them, 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 assemblages are likely shaped not only by local forest structure, but also by the surrounding landscape. Abundance of forest specialists correlates with forest structure; yet, structure is an insufficient predictor of species occurrence and hence, of species richness.

The first doctoral researcher, Marco Basile, assessed how retention elements across the landscape influence occurrence and abundance of forest birds. Describing patterns of bird-habitat relationships, however, cannot reveal the mechanisms shaping local bird communities.

Therefore, in his doctoral project, Joao Pereira is currently focusing on functional responses of birds to forest structure, namely their trophic linkages (and in particular food resource availability), with the goal of shedding light on the ecological processes producing the numerical patterns observed by Marco.

Finally, in the third doctoral project, by making use of the full multi-year series of repeated bird surveys on all ConFoBi plots, B6 plans to analyse the spatio-temporal dynamics of the bird assemblage across the study landscape, and to critically evaluate the commonly assumed indicator function of birds for overall biodiversity.


Research questions and hypotheses

B6 addresses the overall hypotheses that 1) the effects of stand-scale retention measures for biodiversity on forest bird communities are moderated by the surrounding landscape; that 2) patterns in the occurrence and abundance of forest birds in relation to multi-scale forest structure can be explained by their trophic relationships; and 3) that spatial heterogeneity is a predictor of temporal heterogeneity. In particular, we expect that:

  • The 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;
  • Structural heterogeneity, thought to be favoured by retention practices, promotes invertebrate food availability for late-successional forest birds.
  • There is significant inter-annual variation in the abundance and richness of bird species, which is moderated by stand- and landscape-scale forest structure.
  • Forest bird variables (abundance, richness, diversity; red-list, specialists, guilds) are only marginally correlated to diversity-measures for other forest taxa; therefore, their common use as indicators of overall biodiversity is questionable.


Approach, methods and linkages

B6 assesses the structural correlates of avian biodiversity at multiple spatial scales by relating plot-scale presence, abundance and species richness (overall, functional groups and red-listed species) of birds to the abundance, heterogeneity and spatial distribution of structural elements at plot to landscape scales.

B6 annually collects point count data on the full bird assemblage at all 135 ConFoBi study plots and their surroundings. Data will be analysed using multivariate modelling approaches. Currently, the foraging study focuses on two groups of forest birds, representing a large portion of the breeding bird assemblage, and on the corresponding prey: 1) ground foragers and ground-dwelling invertebrates; 2) canopy foragers and canopy-dwelling invertebrates. Ground-dwelling invertebrates are sampled with pitfall traps (with B2, B3 and B4), and canopy-dwelling invertebrates with a combination of caterpillar frass collectors and blacklight traps (with B5). Abundance of prey items will then be related to habitat features, and to abundance of corresponding bird species. 

B6 provides repeated bird count data for all 135 ConFoBi plots to the ConFoBi data pool; cooperates in invertebrate sampling with projects B2-5, and for the predation study with A2. B6 makes use of forest structural data and remote sensing products from A1. Models of multi-scale bird-forest relationships will also be validated using existing data from the Cost Action BOTTOMS-UP database.



B6’s first PhD student Marco Basile has assessed the association of forest bird species with specific microhabitats, as well as the co-occurrence of birds, bats, and invertebrates with microhabitats. Analyses for individual species showed, for example, that woodpeckers select cavity trees not by their absolute size, but their relative dimension: it doesn’t matter how big the tree is, but only that it is bigger than the others. Analyses of the contribution of landscape patterns to plot-scale bird species diversity showed that higher habitat heterogeneity, often resulting from an increase in the share of broadleaved-forest in the landscape, are related to higher bird abundances, richness and diversity.

Distance between forest patches is associated with lower bird richness and diversity and with the overall species turnover. Further, in a meta-analysis, B6 found that various bird guilds show different responses to retention forestry. In cooperation with other ConFoBi projects, B6 assessed the potential of diverse forest management regimes for securing tree microhabitats and bird abundance under climate change, as well as the implementation of socially optimal biodiversity levels in multiple-use forest management plans.

B6’s second PhD student João Pereira is currently analyzing data on forest bird and invertebrate abundances and forest structure. Preliminary data exploration points at a relevant role of within-stand heterogeneity, in particular canopy closure, in promoting ground-dwelling insect abundance, and in turn a more abundant and diverse ground-foraging bird assemblage. A short study on bird-caterpillar interactions using dummy prey indicates markedly different predation intensity across vegetation layers and among trees within each plot, determined by individual tree structure. A global meta-analysis on effects of trophic limitation in the breeding success of forest birds is also being carried out, aiming to shed light into the relative roles of predation and food supply on different guilds of forest birds.


Future projects

Next PhD project (starting 1 July 2022)

Initially, B6 focused on the linkages between multi-scale (plot to landscape) forest structures and bird occurrences, abundance, as well as species assemblages, richness, and diversity. On this basis, B6 has been concentrating on specific inter-trophic relationships that may explain the results observed in the first years. In the final doctoral study (Phd3), B6 proposes to analyse temporal and spatial dynamics of the bird community with regard to forest structure, dead wood, and habitat trees, and to critically assess the effectiveness of birds as biodiversity indicators in forests. In particular, PhD3 will:

  • continue bird surveys on all ConFoBi plots applying the methods established by the previous PhD students. This will allow developing a more robust data base on the linkages between habitat structure and bird diversity, and to analyse temporal and spatial dynamics of the bird community with regard to forest structure, dead wood, and habitat trees;
  • assess the relative importance of landscape composition vs. landscape-scale availability of forest structures (such as deadwood and habitat trees) for the composition, abundance and richness of bird assemblages, by relating bird data to existing multi-scale forest data;
  • address the hypothesis that spatial heterogeneity is a predictor of temporal heterogeneity and therefore an early indicator of regime shifts (Collins et al. 2018, Ecology). PhD3 will assess whether spatial heterogeneity in forest structure (at plot to landscape scales) and/or in bird assemblage composition is related to temporal heterogeneity of bird assemblages. Based on the 135 ConFoBi plots, data on forest and landscapes structure will be related to bird surveys which were replicated annually since 2017;
  • critically evaluate the indicator function of birds for overall biodiversity. Because birds are popular and accessible, they are commonly used as biodiversity indicators in conservation policy and management (e.g. Gregory 2006, Significance). For example, the German nature conservation authorities use trends of selected bird species as indicators of the status of habitat types, including forests ( ConFoBi offers unique multi-taxon data to evaluate this hypothesized indicator function for forest birds. In cooperation with other ConFoBi projects, PhD3 will relate bird variables (abundance, richness, diversity; red-list, specialists, guilds) to diversity-measures for multiple other taxa. Birds should be predictive of the majority of other taxa, if their use as indicators of overall biodiversity was justified.

Finally, B6 aims to provide forest managers with quantitative threshold values for the abundance and configuration of stand-scale and landscape-scale structural habitat elements in favour of forest bird species and communities, and contribute expertise on birds to recommendations for optimizing retention forestry approaches and measures for overall biodiversity conservation. Skills required for PhD3 applicants in B6: in addition to the general requirements described in the job advertisement, applicants who wish to apply for B6 should bring ornithological skills including survey methodology, good knowledge of Central European forest bird communities, and hold a driving licence.

Skills required for PhD3 applicants in B6:

In addition to the general requirements described in the job advertisement, applicants who wish to apply for B6 should bring ornithological skills including survey methodology, good knowledge of Central European forest bird communities, and hold a driving licence.



ConFoBi publications by B6

Asbeck, Thomas; Basile, Marco; Stitt, Jessica M.; Bauhus, Jürgen; Storch, Ilse & Vierling, Kerri T. (2020). Tree-related microhabitats are similar in mountain forests of Europe and North America and their occurrence may be explained by tree functional groups. Trees, 34, 1453–1466.

Asbeck, Thomas; Sabatini, Francesco; Augustynczik, Andrey L. D.; Basile, Marco; Helbach, Jan & Jonker, Marlotte et al. (2021). Biodiversity response to forest management intensity, carbon stocks and net primary production in temperate montane forests. Scientific reports, 11, 1625.

Augustynczik, Andrey L. D.; Asbeck, Thomas; Basile, Marco; Jonker, Marlotte; Knuff, Anna & Yousefpour, Rasoul et al. (2020). Reconciling forest profitability and biodiversity conservation under disturbance risk: the role of forest management and salvage logging. Environ. Res. Lett., 15, 0940a3.

Augustynczik, Andrey Lessa Derci; Asbeck, Thomas; Basile, Marco; Bauhus, Jürgen; Storch, Ilse & Mikusiński, Grzegorz et al. (2019). Diversification of forest management regimes secures tree microhabitats and bird abundance under climate change. The Science of the total environment, 650, 2717–2730.

Augustynczik, Andrey Lessa Derci; Gutsch, Martin; Basile, Marco; Suckow, Felicitas; Lasch, Petra & Yousefpour, Rasoul et al. (2020). Socially optimal forest management and biodiversity conservation in temperate forests under climate change. Ecological Economics, 169, 106504.

Basile, Marco; Asbeck, Thomas; Cordeiro Pereira, João M.; Mikusiński, Grzegorz & Storch, Ilse (2021). Species co-occurrence and management intensity modulate habitat preferences of forest birds. BMC biology, 19, 210.

Basile, Marco; Asbeck, Thomas; Jonker Marlotte; Knuff, Anna K.; Bauhus, Jürgen & Braunisch, Veronika et al. (2020). What do tree-related microhabitats tell us about the abundance of forest-dwelling bats, birds, and insects? Journal of environmental management, 264, 110401.

Basile, Marco; Asbeck, Thomas; Pacioni, Cesare; Mikusiński, Grzegorz & Storch, Ilse (2020). Woodpecker cavity establishment in managed forests: relative rather than absolute tree size matters. Wildlife Biology, 2020.

Basile, Marco; Mikusiński, Grzegorz & Storch, Ilse (2019). Bird guilds show different responses to tree retention levels: a meta-analysis. Global Ecology and Conservation, 18, e00615.

Gustafsson, Lena; Bauhus, Jürgen; Asbeck, Thomas; Augustynczik, Andrey Lessa Derci; Basile, Marco & Frey, Julian et al. (2020). Retention as an integrated biodiversity conservation approach for continuous-cover forestry in Europe. Ambio, 49, 85–97.

Kirsch, Jennifer-Justine; Sermon, Jana; Jonker, Marlotte; Asbeck, Thomas; Gossner, Martin M. & Petermann, Jana S. et al. (2021). The use of water-filled tree holes by vertebrates in temperate forests. Wildlife Biology, 2021.

Storch, Ilse; Penner, Johannes; Asbeck, Thomas; Basile, Marco; Bauhus, Jürgen & Braunisch, Veronika et al. (2020). Evaluating the effectiveness of retention forestry to enhance biodiversity in production forests of Central Europe using an interdisciplinary, multi-scale approach. Ecology and evolution, 10, 1489–1509.