How High Nature Value (HNV) farmland is related to bird diversity in agro-ecosystems – Towards a versatile tool for biodiversity monitoring and conservation planning

•High Nature Value farmland in Germany was surveyed at a very detailed scale.•The approach was evaluated by relating it to bird diversity in agro-ecosystems.•The scale of the survey seemed too small to reflect habitat for endangered birds.•Data clustered to landscape types provided a versatile tool for nature conservation. Within the European Union, national approaches of a ‘High Nature Value (HNV) farmland’ indicator have been developed to inform about the potential of agricultural landscapes to maintain biodiversity. We assessed how bird species abundance, richness and community composition, particularly of specialist species, were associated with the German HNV farmland indicator as an area-based aggregate and with its particular components which were semi-natural landscape elements and agricultural patches with characteristic plant species mapped in representative sample plots. The aggregated HNV indicator score showed a weak but positive relationship with generalist bird species only, while specialist species were associated with individual HNV farmland features characterizing wet grasslands and open farmland. Bird community analysis revealed three groups of HNV farmland features representative of particular landscape types: (1) complex landscapes with vertical woody structures such as hedgerows or small woodlands, (2) wet grasslands and (3) open agricultural land of low land-use intensity. Large portions of unexplained variance, however, indicated that the small-scaled HNV farmland features recorded without considering the landscape context may not have fully captured all important drivers of bird diversity in agricultural landscapes. To achieve a better representation of habitat requirements particularly of specialist bird species we propose surveying HNV farmland in a landscape context and calculating landscape-specific scores for highly structured, wetland-dominated and open landscapes of low land-use intensity. As compared to the aggregated indicator, the small-scale HNV farmland survey data would more efficiently enfold its potential for tailoring conservation schemes specifically to a given landscape type and its associated bird species.