The feeding behaviour of Olive-backed Sunbirds (Nectarinia jugularis) in a patch of Scarlet Spiral Flag (Costus woodsonii) was posted earlier – see HERE. It shows how the male, female and male eclipse (pre-adult, non-breeding male) accessed flower nectar. This post provides details of how the three categories of sunbirds sip nectar from the flowers. The video below shows the different sunbirds taking nectar from flowers at close range.
The beginning of the video shows a rare scene of an adult male probing the flower from the top of the flower. This is the conventional way of nectar harvesting. As the bill enters the flower, it passes through the ring of anthers to the flower base where the tongue will collects the nectar. As the sunbird leaves the flower to visit another, its bill, dusted with pollen will transfer some to the stigma of the next flower – see HERE for details of the flower.
For whatever reasons, most of these sunbirds fail to collect nectar this way. Instead, they pierce through the base of the flower petals to short-cut the process. In this way the sunbirds are not helping in the pollination of these flowers. Such nectar robbing or stealing has become popular with the Olive-backed Sunbirds.
Olive-backed Sunbirds similarly rob nectar from Ornamental Banana (Musa ornate) flowers LINK. But in this case the flowers are longer than the bill of the sunbirds. Not so in the case of flowers of Scarlet Spiral Flag.
Pre-adult males (male eclipse) similarly rob nectar. These are the young sunbirds whose breeding plumage has yet to be fully formed – the blue-black forehead, throat and breast have yet to be formed. Only patches of black can be seen on the yellow belly. Depending on how young these male eclipse is, it may show confusion on how to access the flower nectar.
Male eclipse with blue-black stripe at the centre of the throat appears to be more experienced than the younger male eclipse with only slight blue-black patch on the throat. The last segment of the video shows this young male spending a long time puzzling on how to access the nectar.
YC Wee
Singapore
16th July 2018
