Habitat and habitat management requirements of the shrill carder bee (bombus sylvarum) and the brown-banded carder bee (bombus humilis) in South Essex

A study of the habitat and habitat management requirements of two UK Biodiversity Action Plan Priority bumblebee species, Bombus sylvarum and Bombus humilis. Maps were produced of the South Essex distributions of the bees and a combination of field surveys, pollen sampling, habitat manipulation and microsatellite DNA analysis were used to investigate the forage requirements, nestingp referencesa nd spatiald ynamicso f the bees. Bombus humilis and B. sylvarum queens were recorded as the latest emerging of the Bombus species observed, not appearing until late May. Fabaceae, Scrophulariaceae and Lamiaceae were recorded as being the floral families most frequently and consistently visited by the bees with pollen being most commonly collected from Fabaceae and Scrophulariaceae. Rarefaction analysis of dietary preference data revealed that the mean number of plant species B. sylvarum workers would be expected to visit during 20 flower visits was significantly fewer than for B. humilis and B. pascuorum (p=0.009 and p=0.004 respectively). The mean number of plant species B. humilis would be expected to visit during 20 flower visits was similar to that of the nationally ubiquitous species B. pascuorum and B. lapidarius but was consistently lower than another ubiquitous species B. terrestris/lucorum, although not significantly so (p=0.182). Forage patches sown with favoured forage species of the bees (Lotus glaber, Odontites verna, Ballota nigra, Lotus corniculatus and Trifolium pratense) successfully attracted B. humilis and B. sylvarum workers. No technique was found for reliably locating nests, and only three nests were located in the study. Those that were found were situated in relatively undisturbed tall rough grassland with a sunny exposure. For the first time, microsatellite DNA analysis was used to assess foraging distances of rare bumblebees. Mean foraging distances estimated from distances separating sister bees were calculated as 756m for B. humilis and 232m for B. sylvarum. These distances were considered to be appropriate spatial scales for nesting and foraging habitat management. Results from this study were fed into a 10-year habitat management program for the bees at Hadleigh Castle Country Park, South Benfleet, Essex.