A four‐year investigation into the efficacy of domiciles for enhancement of bumble bee populations

Abstract 1 Eighty four‐unit domiciles for introduced bumble bees ( Bombus spp.) were placed in 16 field margins at Lincoln, New Zealand in the 1995–96 southern summer. Fifty‐five were placed in the margins of intensively managed fields, with the remaining 25 being in less disturbed habitats, which had more spring/summer floral resources. 2 The number of nests founded over the four‐year study period increased from one to 27. Bombus hortorum was a much more frequent colonist than was B. terrestris , with B. ruderatus colonizing only in the fourth year. 3 In the ‘intensive’ sites, mean four‐year occupancy was only 2%, whereas in the less disturbed sites it was 13%. 4 There was a positive association between bumble bee occupancy of the domicile compartments in the previous year and occupancy in the current year. No association was found between previous occupancy by mice and subsequent occupancy by bumble bees. 5 The potential for adding Bombus nest sites to agricultural land to enhance local populations, and, potentially, pollination of seed crops, is discussed. Adding domiciles in intensively managed landscapes may not be very effective unless spring floral resources are enhanced as well.