Effects of local climate and habitat heterogeneity on breeding-bird assemblages of semi-natural grasslands

Jonas Brüggeshemke,Franz Löffler,Thomas Fartmann,Marco Drung

doi:10.1007/s10336-022-01972-7

Jonas Brüggeshemke, Franz Löffler + Show 2 more

Open Access

https://doi.org/10.1007/s10336-022-01972-7

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Abstract

The intensification of agricultural land-use, abandonment and afforestation have caused severe loss and degradation of nutrient-poor, semi-natural grasslands across Europe. Calcareous grasslands have an outstanding value for nature conservation due to their highly diverse flora and fauna, including birds. However, knowledge of environmental factors driving the composition of bird communities in calcareous grasslands is still scarce. The aim of our study was to compare the breeding-bird assemblages of calcareous grasslands and the second most common semi-natural grassland type in the study area (Diemel Valley, Central Germany), mesic grasslands, along an elevation (climate) gradient. For each grassland type, we randomly selected 27 square-shaped plots with a size of 5 ha each and a cover of the focal grassland type of at least 50% within the plot. Our study revealed that both the number and density of threatened species of breeding birds were higher in plots of calcareous grasslands than in those of mesic grasslands. Based on multivariable generalised linear mixed-effects models, the most important predictors of overall species richness and density of breeding birds in plots of calcareous grasslands were the area of juniper-rich calcareous grassland and Shannon habitat diversity. By contrast, the number and density of threatened species were in both grassland types mainly driven by breeding-season temperature. Heterogeneous, juniper-rich calcareous grasslands seem to be a key habitat for bird assemblages with high species richness and density. These grasslands usually consisted of small-scale habitat mosaics providing suitable nesting sites and foraging grounds in close proximity. By contrast, mesic grasslands had rather homogeneous swards and shrubs or trees were normally restricted to the edges of the grassland patches. Based on our study, increasing habitat heterogeneity at the landscape scale and within grasslands is the key to enhancing species richness and density of breeding birds.

Highlights

Most of Europe’s biodiversity is associated with agricultural land (Donald et al 2006; Henle et al 2008; Kleijn et al 2009)
Our study revealed that both the number and the density of all and threatened species of breeding birds were higher in plots of calcareous grasslands than in those of mesic grasslands
Based on the multivariable generalised linear mixed-effects models (GLMM), the most important predictors of overall species richness and density of breeding birds in plots of calcareous grasslands were the area of juniper-rich calcareous grassland and Shannon habitat diversity

Summary

Introduction

Most of Europe’s biodiversity is associated with agricultural land (Donald et al 2006; Henle et al 2008; Kleijn et al 2009). Traditional farmland-management practices have contributed to the creation of semi-natural ecosystems hosting an outstanding biodiversity (Plieninger et al 2006, 2015; Löffler and Fartmann 2017; Poschlod 2017). The intensification of agricultural land-use, abandonment and afforestation have caused severe loss and degradation of nutrient-poor, semi-natural grasslands across Europe (Wallis De Vries et al 2002; Baur et al 2006; Löffler et al 2020). Calcareous grasslands have an outstanding value for nature conservation due to their highly diverse flora and insect fauna (Poschlod and Wallis De Vries 2002; van Swaay 2002). Previous studies on the biodiversity of calcareous grasslands have primarily concentrated on plants and insects (e.g., Poschlod and Wallis De Vries 2002; Poniatowski and Fartmann 2008; Krämer et al 2012; Helbing et al 2021).

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