The nesting ecology of fossorial solitary bees

In the UK, fossorial solitary bees account for approximately 52% of bee species, but their nesting ecology has received little attention in the academic literature. This research gap is largely a result of logistical barriers, which centre around the difficulties associated with locating nests and the time resources required to collect quality data. It is further compounded by the lack of standardised methodologies associated with this type of analysis. This PhD used three methodological approaches to overcome these obstacles, investigate the efficacy of the methods and shed light on the ecological requirements of fossorial solitary bees. The three principal methods enlisted in this research were a web-based citizen science project, which was linked with a field-based observational study of nest sites and finally a manipulative field experiment. All three of these methods were found to provide important insights into solitary bee nesting ecology and the field study benefitted significantly from being linked with the citizen science project, which provided accurate locations of active nesting sites. The citizen science data demonstrated the capacity of Andrena fulva, Andrena cineraria, Halictus rubicundus and Colletes hederae to nest within a broad range of environmental conditions including slope and ground cover, while the field-based study indicated that high-density nesting relies on the presence of specific environmental characteristics, such as bare ground and sandy soil. Significant interspecific differences in nesting characteristics were also identified indicating the need for further study of individual species. The field experiment found that the creation of bare ground and the maintenance of vegetation at a low level increased the nesting density of fossorial species six-fold. This research has explored and interrogated the efficacy of these three methodological approaches. Furthermore, it has elucidated some of the important environmental considerations for the protection and provision of suitable solitary bee nesting sites.