Aggressive displacement of Xylocopa nigrita carpenter bees from flowers of Lagenaria sphaerica (Cucurbitaceae) by territorial male Eastern Olive Sunbirds (Cyanomitra olivacea) in Tanzania

Abstract

Male Eastern Olive Sunbirds (Cyanomitra olivacea) and Xylocopa nigrita carpenter bees in Tanzania both utilise the flowers of male plants of Lagenaria sphaerica (Cucurbitaceae) as a source of nectar. The sunbirds set up territories defending this nectar resource.  Observations of interactions between the sunbirds and the carpenter bees show that the bees are aggressively displaced from flowers when spotted by the birds.  Only the bees can be considered as legitimate pollinators as the birds do not contact the anthers of the male flowers and were never seen visiting nectarless female flowers of Lagenaria sphaerica.  Such territory defence may have implications for the frequency of movement and composition of pollen being transferred from male to female flowers which warrants further research.