Dendrophthoe pentandra is a common mistletoe plant that is semi-parasitic on wayside trees (above left). The mistletoe is spread by flowerpeckers and sunbirds that eat the fruits and excrete the sticky seeds when perching on the branches of shrubs and trees. These seeds are excreted stuck together, as the gummy covering that originally covered the seeds remain intact when passing through the digestive tract.
Now what do these birds do? Some simply wipe their bottoms against the branch to dislodge the seeds. Others use their beak or foot to remove the seeds from the posterior opening. In the process, these sticky seeds end up on the surface of the
branch where they slowly develop, sending a ‘sucker’ into the host’s tissues to tap water and nutrients. Green leaves develop so that the mistletoe can photosynthesise. It is thus partially parasitic on the host but it can do much damage in the long term.
In due course the mistletoe flowers (above right). These are so-called exploding flowers that need birds to trigger their opening. The images on the left show the Olive-backed Sunbird (Cinnyris jugularis) with its bill clamped on the flower bud. The pressure exerted on the bud will cause the flower to ‘explode’ and the petals to unfold. This allows the sunbird to insert its tongue into the flower to harvest the nectar.
An earlier post shows the Blue-crowned Hanging Parrots (Loriculus galgulus) harvesting nectar from the other mistletoe, Macrosolen cochinchinensis. As the bill of the parrot is differently constructed from that of sunbirds and flowerpeckers, the parrot needs to get at the nectar from the side of the flower, with the help of its broader tongue.
The images below show a male (left) and a female (right) Scarlet-backed Flowerpecker (Dicaeum cruentatum) among the Dendrophthoe pentandra mistletoe, obviously harvesting nectar. I am sure the birds need to use their bill to force the bud to open before they can get at the nectar, as with the sunbirds. However, I have yet to have photographic evidence.
In all three cases (sunbird, flowerpecker and parrot), the birds assist in the pollination of the mistletoe flowers, bribed by the offer of nectar.