Assessing the value of Rural Stewardship schemes for providing foraging resources and nesting habitat for bumblebee queens (Hymenoptera: Apidae)

Abstract

Bumblebees (Bombus spp.) play a key role within agricultural systems as pollinators of crops and wild flowers. However, this taxon has suffered severe declines as a result of agricultural intensification. Conservation efforts largely focus on providing forage resources for bumblebees through the summer, but providing suitable habitat during the period of nest foundation in early spring could be a more effective method of boosting local bumblebee populations. This study assesses the attractiveness of three different farmland habitat types (hedgerow, field margin and grassland), and the relative merits of respective land management prescriptions under the Scottish Rural Stewardship scheme to nest site searching and foraging bumblebee queens during the period of queen emergence and colony foundation. Hedgerows were the least attractive habitat type to spring queens. Rural Stewardship species-rich grassland comprised a complex vegetation structure attracting nest site searching queens, whilst grassland that had been abandoned allowing natural regeneration contained more flowers, attracting foraging queens. Field margin habitats were the most attractive habitat type, and Rural Stewardship field margins attracted both nest site searching and foraging queens at relatively high densities. This management option consisted of a sown grass mix, giving rise to the complex vegetation structure preferred by nest site searching queens, but regular disturbance allowed invasion by early flowering bumblebee forage plants. These findings suggest that it should be possible to develop simple combined management strategies to provide both suitable nesting sites and spring forage resources on farmland, promoting bumblebee colony foundation and therefore abundance in the agricultural environment.