Agri-evironmental schemes and active nest protection can increase hatching success of a reintroduced farmland bird species

Throughout Europe ground-nesting farmland bird species are rapidly declining and have become a conservation concern. Intensive agriculture and high nest predation rates are major factors causing the decline. Species conservation efforts often focus on habitat enhancement to increase the quantity and quality of available habitat structures (habitat enhancement hypothesis) or active nest protection by fencing and predator control (predation mitigation hypothesis). Within the context of a reintroduction project of grey partridges (Perdix perdix) into two regions of Switzerland, we investigated breeding habitat preferences and hatching success in relation to properties of the habitat surrounding the nest. Then we tested whether predator exclusion by fencing can increase hatching success. The location and hatching success of 121 nests were observed by radio-tracking and available habitats in both regions were mapped. Grey partridges preferred nesting habitats in highly heterogeneous wildflower areas, which had been implemented as biodiversity promoting areas (BPA) and nest fencing significantly increased hatching success. Likewise, increased proportions of wildflower BPAs tended to enhance hatching success, which is probably related to higher availability of cover in these structures. Increasing proportions of cover vegetation around the nest had a positive effect on hatching success. Increasing the quality of rural habitats by providing heterogeneous habitat structures as well as reducing predator access to nests by fencing can increase hatching success in grey partridges and is likely to benefit other ground-nesting birds as well. In fact, high amounts of cover vegetation around the nest can compensate for nest fencing by hampering nest depredation.