wetlands
a publication of Sungei Buloh Wetland Reserve

Vol 9 No 3

otters: water puppies of the reserve

Hillgrove secondary school adopts the reserve

singapore's first wetland reserve:
what does this mean?

reintroduction of
native mangrove flora

some interesting notes on
the sunbirds

volunteer training at mawai eco camp

Commonwealth secondary school student volunteers

home on high
 
some interesting notes on
the sunbirds

by james gan
senior conservation officer

Among the many resident bird species that inhabit the Sungei Buloh Wetland Reserve (SBWR), the sunbirds possess one of the most brilliantly coloured plumage. The bright colours are found only on the adult males with the females and young males clad mainly in varying hues of olive, green and yellow. Belonging to the family Nectariniidae, sunbirds are distributed from Africa to Asia and Australia. In Singapore, six species of sunbirds occur, of which four have been recorded at SBWR. That is about 4% of the total sunbird species worldwide. Of the four species, the most abundant at SBWR is the Brown-throated, also known as the Plain-throated Sunbird (Anthreptes malacensis). The Olive-backed Sunbird (Nectarinia jugularis) is the next most numerous followed by the Copper-throated Sunbird (Nectarinia calcostetha) and the Crimson Sunbird (Aethopyga siparaja).

Sunbirds are essentially nectar feeders, but they are also known to take small insects. Superficially resembling the well-known hummingbirds of Central and South America, sunbirds however have strong feet and legs and have short rounded wings. Sunbirds have relatively long, slender decurved bills that enable them to probe into suitable flowers for nectar.

Their nests are unusual. Generally pear-shaped, globular or oval and composed of grass, fibres and cobwebs, they are usually suspended from the ends of terminal twigs. Clutches of two eggs is typical.

The survival of sunbirds has been monitored at SBWR through ringing studies. Although very small and active, sunbirds are known to have long lives in the wild. For example, the Brown-throated Sunbird, has been known to live for at least 61 months (5 years) in SBWR while studies in other localities have revealed lives exceeding 12 years! For the other species, SBWR has recorded (between ringing and subsequent capture) durations of 60 months (5 years) for the Olive-backed Sunbird and 61 months (5 years) for the Copper-throated Sunbird.

The Copper-throated Sunbird (Nectarinia calcostetha) is one of the more interesting species. Found only in South-east Asia, they live within the mangrove forest. They are one of the few bird species that are global mangrove specialists. Nesting on mangrove trees like Avicennia alba they feed from the flowers of mangroves like the Bruguiera gymnorhiza. Males have iridescent coppery red throats with iridescent green on the crown, shoulder and uppertail. Females have white throats and are mostly decorated in grey and yellow. They are sexually dimorphic with adult males being about 10% longer and 20% heavier than adult females. Nests have been seen in the reserve between April and August and it has been known to nest from January to September in other localities.

Perhaps the most abundant sunbird at the wetland, the Brown-throated Sunbird, can be seen in all areas of SBWR. It is also the largest sunbird species in SBWR (and Singapore). Weighing in at a maximum of 14.0g, males are generally larger than females especially in terms of body length. Possessing reddish eyes (iris) when they are adults (the other three species have dark brown eyes), they have olive brown eyes as juveniles.

What about the smallest sunbird species in SBWR? Either the Crimson Sunbird or the Olive-backed Sunbird qualifies. These two species also share a common characteristic that is the exhibition of an eclipse plumage in the males. This is essentially a short-term post-breeding plumage. Whatever the plumage type, the adult male Crimson Sunbird appears like a tiny red dot amongst the vegetation. It weighs about 7.0g (about the weight of a 50 cent coin) with females being slightly lighter. The females have the dubious honour of having perhaps the dullest plumage of any sunbird in the region with only dull olive and yellow to adorn herself.

The Olive-backed Sunbird is more abundant than the Crimson Sunbird. Many of them can be seen flitting among the flowering trees at the Visitor Centre complex especially on sunny days.

There is no doubt that the sunbirds as a group add life, colour and sound to the green vegetation in SBWR and Singapore in general. Generally, to attract and encourage sunbird populations to increase, it is important to cater to their food and nest requirements. Suitable free flowering trees and plants provide abundant nectar as food. Many types of trees may also be used as nest sites while grass patches serve to provide building material for the nest. SBWR has taken these measures and the population of sunbirds at the site serve as an indicator of the success of these measures. More studies await those interested in understanding especially the population dynamics, species interactions and carrying capacities of these sunbirds at SBWR.


At a Glance (data based on ornithological field studies undertaken by SBWR)
Species
Total Body Length (mm)
Wing Length (mm)
Weight (g)
Brown-throated Sunbird
Adult Male (n=13)
130 - 139
60 - 69
10.0 - 14.0
Adult Female (n=14)
122 - 130
58 - 67
9.0 - 12.0
Copper-throated Sunbird
Adult Male (n=5)
133 -139
58 - 60
8.0 - 10.0
Adult Female (n=4)
123 -128
54 - 57
7.0 - 8.0
Olive-backed Sunbird
Adult Male (n=6)
110 -118
50 - 55
7.0 - 10.0
Adult Female (n=5)
105 -115
50 - 53
7.0 - 10.0
Crimson Sunbird
Adult Male (n=2)
115 -117
51
7.0
Adult Female (n=1)
104
47
6.0
   
© Sungei Buloh Wetland Reserve