Borneo Spiderhunters

On our fabulous island of Borneo, most nature lovers know the popular spider hunters by their long beaks and loud calls. They are common around our gardens, the forests and areas where the environment is reclaiming the land.
Biologically, they are part of the familiar sun bird family (Nectariniidae), the males and females look the same and both sexes incubate eggs. They are not picky eaters consuming most insects and enjoy the nectar of many flowers. They have the uncanny ability to pluck a spider from the center of a web and not become entangled.
In a recent scientific paper, Dr. Robert G. Moyle and his team of world renowned scientists including our own Mustafa A. Rahman from the University of Malaysia Sarawak, explained how the spider hunters how they diversified.. There are eleven species scattered throughout our region and the researchers studied how they are related to each other and how they arrived to where they are today.
During the last ice age, about 20,000 or so years ago, ocean water became frozen lowering the depths of the seas. Land became exposed and the South China Sea and Straits of Malacca became a marshy reedy swamp. Sumatra, the Malay Peninsula, Borneo and Java plus all the smaller islands became connected.
Collectively, the area is called Sundaland named after the plate on which they ride. The edges of the plate form parts of the famous Ring of Fire known for earthquakes and volcanic eruptions. There are exceptions to the Sunda land mass. The waters around Sabah are too deep and were not connected. The Philippines are oceanic and have never been bridged.
The Straits between Java and Lombok are one deepest part of the seas and this division is known as Wallace’s Line.
Also during this period, the tops of mountains became cooler and dryer. Montane vegetation changed and moved down the slopes connecting previously isolated mountain ecosystem.Over the years, the animals became isolated by the mountain barriers and formed separate species. The lowland rainforest was restricted to isolated refuges around the coast of Borneo, in Western Sumatra and the Malay Peninsula. Populations in these isolated lowland forests have recently come back together, meeting in a hybrid zone near the Sabah-Sarawak border.
By catching spiderhunters in nets and collecting a few drops of blood and tissue samples or scouring museums and laboratories for tissue samples, the compared DNA from the nucleus and the mitochondria (remember the power house of the cell?). Just like the DNA can tell who your brother or sister is as compared to a stranger, it also informs about the relationship among the spider hunter species.
There are many Spider Hunters that nest in Borneo. The one found only on our island resides in the highlands of Sabah and North Sarawak. A unique creature, Whiteheads spiderhunter (A. juliae), is different from all the others because it is dark brown instead of green and has a streaky under belly.
There has been considerable confusion and controversy about the Gray- Breasted Spiderhunter (formerly, A. affinis). We now know it comprises of two species: the Streaky-breasted Spiderhunter (A.everetti) lives in the highlands of Borneo quite possibly because of isolation during the ice age. The Gray-breasted Spiderhunter (A. Modesta) lives in the lowlands.
There are many other interesting facts discovered by the scientists presented in this paper. The Spider Hunters can be divided into the three groups based on their relationships. See Table 1.
In a huge surprise, the Purple naped sun bird ( Nectariidae Hypogramma hypogrammicum) was found to be much closer, DNA speaking, to the spiderhunters than the sunbird. The similarities seem obvious when one thinks about it the authors point out. They both live in the same areas. Some species of Spiderhunters have under belly streaking. Both built similar purse nests under large leaves. It is roughly the same size as a couple of spiderhunter species. The authors caution, however, more research needs to be conducted before a genus shift should be further considered.
Grab you binoculars, insect repellant, hiking shoes and bird guide and head out to find the magnificent Spiderhunters. For a few species, you probably won’t have to leave the city and town areas where you live.
Information of this article was adapted from:
Moyle, Robert et al. 2011 Diversification of an endemic Southeast Asian Genus: Phylogenetic Relationships of the Spiderhunters (nectariniidae: Arachnothera) The Auk vol.128, no. 4, p. 777-778