Abstract
Across Europe, patches of un‐cropped land (field margins, fallows, etc.) have been established and managed as part of agri‐environment schemes (AES) to counteract the decrease in farmland biodiversity. Various studies demonstrate a positive impact of such un‐cropped land on different taxa. However, there is potential to further improve the efficiency of fallow options for farmland birds. In a long‐term monitoring, 12 breeding farmland bird species and sizes of perennial fallows were recorded from 1992 to 2015 in a 6.1 km2 area in Switzerland. Furthermore, habitat composition and fallow characteristics were mapped in 2012. We calculated population trends, analyzed habitat associations and revealed the impact of fallow habitat characteristics on territory density. The proportion of fallows in the study site increased from 1.4% (1992) to 8.5% (2012). Population trends of six of 12 censused species increased significantly over the same time, four species showed no trend and trends of two species decreased. Seven species were analyzed in more detail, for five of them fallows were overrepresented around their territory center points compared to arable fields and grassland. The overall territory density of these five species was higher in small fallows which were not placed next to a wood and which held bramble rubus spp., shrubs and the tall‐growing forb goldenrod (Solidago canadensis and S. gigantea). Our study confirms that perennial fallows are a highly suitable option to support different farmland birds in arable landscapes. Yet, we recommend optimizing fallows through careful site selection and management, such that they are not established on shady locations and are structurally diverse by allowing brambles, shrubs, and tall‐growing forbs to occur. We suggest adapting the Swiss AES in this regard. Biodiversity‐related advisory services available for farmers could increase the probability that fallow options are implemented and managed properly for targeted species.
Highlights
| METHODSWe conducted our study in the very southwest of the Swiss lowland, the Champagne genevoise (420–450 m a.s.l., 46°09′11′′N, 6°01′25′′E, canton Geneva), which has a warm and dry climate (mean temperature is 11.2°C, mean yearly precipitation is around 700 mm)
Seven species were analyzed in more detail, for five of them fallows were overrepresented around their territory center points compared to arable fields and grassland
Our study confirms that perennial fallows are a highly suitable option to support different farmland birds in arable landscapes
Summary
We conducted our study in the very southwest of the Swiss lowland, the Champagne genevoise (420–450 m a.s.l., 46°09′11′′N, 6°01′25′′E, canton Geneva), which has a warm and dry climate (mean temperature is 11.2°C, mean yearly precipitation is around 700 mm). We analyzed the association of birds with the different habitat categories in 2012 (Table 1) with a compositional analysis (Aebischer, Robertson, & Kenward, 1993; Calenge, 2011; package “adehabitatHS”) This was performed for the seven species with more than 20 territories (based on the recommended sample sizes in Aebischer et al, 1993): Common Whitethroat, European Stonechat, Melodious Warbler, Yellowhammer, Red-backed Shrike, Corn Bunting, and Skylark. For four of the seven analyzed bird species (Whitethroat, Stonechat, Melodious Warbler and Red-backed Shrike) fallows ranked first before all other habitat categories, that is, fallows were strongly overrepresented in the pseudoterritories The final model revealed that the density of bird territories was strongly influenced by size, distance to wood, and vegetation composition (proportion of bramble, goldenrod, and shrubs) of the fallows (Table 4). The least influential (nonsignificant) explanatory variables were age (positive) and the proportion of grasses (negative)
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