Patches of bare ground as a staple commodity for declining ground-foraging insectivorous farmland birds.

Michael Schaub,Nadja Weisshaupt,Niklaus Zbinden,Aline Tagmann-Ioset,Melanie L Maurer,Raphaël Arlettaz,Fitsum Abadi,Lukas Jenni,Thomas S Reichlin,Nicolas Martinez,Darren Mark Evans

doi:10.1371/journal.pone.0013115

Abstract

Conceived to combat widescale biodiversity erosion in farmland, agri-environment schemes have largely failed to deliver their promises despite massive financial support. While several common species have shown to react positively to existing measures, rare species have continued to decline in most European countries. Of particular concern is the status of insectivorous farmland birds that forage on the ground. We modelled the foraging habitat preferences of four declining insectivorous bird species (hoopoe, wryneck, woodlark, common redstart) inhabiting fruit tree plantations, orchards and vineyards. All species preferred foraging in habitat mosaics consisting of patches of grass and bare ground, with an optimal, species-specific bare ground coverage of 30–70% at the foraging patch scale. In the study areas, birds thrived in intensively cultivated farmland where such ground vegetation mosaics existed. Not promoted by conventional agri-environment schemes until now, patches of bare ground should be implemented throughout grassland in order to prevent further decline of insectivorous farmland birds.

Highlights

Farming practices have changed radically since World War II, provoking an unprecedented crisis for farmland biodiversity [1]
The common preference seen in all four bird species for bare ground across the different types of farmland habitats suggests that food availability is of paramount importance for habitat selection [28,29]
The question arises as to how abundant the prey supply must be in the ground vegetation and how patches of bare ground must be distributed within the agricultural matrix to offer suitable conditions for these birds

Summary

Introduction

Farming practices have changed radically since World War II, provoking an unprecedented crisis for farmland biodiversity [1]. The total area devoted to agricultural production has increased through the conversion of pristine habitats into grassland or arable land [2]. Fertilizers have substantially increased the yields per unit of land and time: the resulting sward thickening has changed micro-climatic conditions within grassland, thereby lowering invertebrate abundance and reducing accessibility for many organisms [4,5]. Agricultural development has dramatically increased the human share of net primary productivity (NPP) at the biosphere scale (currently about 50% of continental NPP [7]). This diversion of NPP for the sake of humans has benefited our rapidly growing population by substantially increasing food supply; it has caused large-scale biodiversity erosion

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