The unsung avian heroes of pollination. The bulk of our Southern African flowering species of plants (some 80% of the total) relies on insects as their primary pollen vectors.
We generally associate bees with pollination and rightfully so as they do make up the largest and probably the most important group of insect pollinators. However, there is a vast array of other insects including butterflies and moths that make an enormous contribution to flower pollination some having complex mutualisms including rewards to the pollinator. A few rare species of aloe are solely dependent on insects for pollination.
There is also a significant number of flowering plants in South Africa (estimated to be between (2% and 4% depending on the size and diversity of a particular regions’ floral kingdom) that have adapted to bird pollination. They supply copious amounts of nectar to feeding birds and all they ask for in return is that their pollen is spread far and wide to ensure successful pollination. It is amazing how certain genera or even groups of genera have become specialized to accommodate pollination by birds.
Unlike the nectarivores of the new world like hummingbirds which can hover and are able to extract nectar from long straight tubular flowers our sunbirds need to perch when feeding. This requirement has resulted in most of our bird-pollinated flowers having slightly, curved and downward facing tubes and rigid stems to accommodate dedicated nectarivores like the sunbirds and sugarbirds. There has been a long-standing belief that sunbirds are the only avian species that pollinate our trees and flowers.
While the aforementioned species probably make up the most important contribution to pollination, there is
a large group of about 70 known species of occasional nectarivores that make a significant contribution to pollination in South Africa.
Researchers have found that deep narrow tubular flowers are generally the ones visited by dedicated avian nectarivores while the wider and shorter tubular flowers are the ones pollinated by occasional nectarivores, an adaption to their shorter bills and tongues. This makes sense as when they do happen to visit short tubular flowers there is no transfer of pollen from the reproductive parts of the flower onto their heads and as a result, they provide no benefit to the flower at all.