Evidence for passerine bird pollination in Rhododendron species

It has been hypothesized that flowering plants at high elevation could be pollinated by local passerine birds given that low temperature limits insect activity. In particular, species with large flowers are likely to be pollinated by large-body animals because a morphological fit between floral morphology and pollinator body could facilitate pollen transfer. Huang et al. investigated pollinator species and their visitation frequency in 15 Rhododendron species from East Himalayas. The pollinator experiments excluding all pollinators, or just birds in the 15 species demonstrated that birds acted as pollinators in 2/3 studied Rhododendron species, in support of the hypotheses.