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

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.

Figure 1. Marginal selection probability of foraging locations in relation to amount of bare ground and vegetation height for four farmland bird species.

Predictions are revealed from the best models (see the supporting information) and refer to hoopoes (black dots), wrynecks (blue triangles), woodlarks (red squares) and common redstarts (green diamonds). Note that selection probabilities below 0.5 indicate avoidance, selection probabilities above 0.5 indicate preference. Points are posterior means, vertical lines show the limits of the 80% credible intervals.