Africa to Borneo – The Magpie Robins

Magpie Robins hop along the forest floor, in gardens and cleared areas with their tails upright. They are one of the first birds the beginning photographer or bird watcher can add to their life list as they stop, scratch at the ground and search for hidden insects and other avian delicacies. Most prefer open forests and coastal areas.
The Shamas, a shy bird, are usually spotted at twilight and dawn in primary and secondary forests. They are known for their long tails and melodious singing. They often imitate the sounds of other birds. The species is nearly extinct in Singapore because they are captured by greedy individuals and sold to the public. The birds are in major decline throughout the region because of the bird pet trade. They are purchased and live only a few months in captivity because the owners soon become bored and they are neglected.
The Magpie-robins and Shamas are thought to have evolved in Southeast Asia from African relatives about 7.2-5.3 million years ago. How and why they arrived is not known but they are genetically closely related to their African, Middle East and south Asian cousins.
Shamas
Once the Shamas evolved, there are two possible scenarios for their further distribution on S.E. Asian Islands. The Philippine varieties were the result of two invasions from Sundaland, the area that encompasses Indonesia to the Wallace Line and Malaysia. The first wave resulted in the white browed Shamas (C. Luzoniensis) an isolated population on the island of Luzon.
The second wave, from Borneo, landed on the islands of Palawan and Cebu. They eventually evolved into C. niger and C. cebuensis.
The second hypothesis on the distribution has the birds arriving very early, about 27 million years ago in the Philippines. From there, they diversified and reinvaded Sundaland via Borneo.
The White Rumped Shama (C. malabaricus) arrived and became isolated in eastern and western Sundaland. The Borneo variety morphed into two separate subspecies, The White-capped (C.m stricklandii) to the north and Black- capped (C.m suavis) on the rest of the island.
Magpie- robins
The Magpie-robins, as good dispensers, arrived from Africa in masse and populated Indian Ocean and Sundaland. On the Philippine Islands they morphed into an all black form (C.mindanesis). Interestingly, they are not on the island of Palawan, maybe because of competition with the Black Shama (C. niger).
The original birds of Borneo and Java were black bellied while white bellied types arose on Sumatra, Malaya and the mainland. The black bellied birds on Borneo further evolved into two subspecies, adamsi in Sabah and pluto on the rest of the island. There is hybridization zone in central Borneo where the black and white forms meet.
The Refugia Hypothesis
This idea came about in 1969 by Jurgen Hafferin describing a possible scenario on the rise of species and sub species in the tropics. During the last ice age, the tropical rain forests were divided into islands by broad expanses of savannah and grasslands. This was because of a cooling and drying period. These isolated rain forests became known as “refugia”.
In each of these separated forests (refugia) the isolated flora and fauna became different unable to move from one area to another and intermingle. As time passed they evolved into separate sub species and species. This occurrence has been used to explain the different orangutan subspecies and ant and rodent species among others.
However, the union of disparate land masses from low sea levels could also explain the spread of different species. Birds could fly over them stopping for food instead of over open water. From Sumatra, the black rumped shama (C.m. suavis) could have spread east to Borneo meeting up with White-capped (C.m. stricklandii). Remember, all the land was connected because the waters were tied up in ice. When the ice melted and warmer temperatures returned, the land bridges were flooded, returning to the familiar map of today.
A huge puzzle yet to be solved is why the lowland species of birds are different in Sabah and not on the rest of the island. For example, both the Magpie-robin (C. saularis adamsi) and Shama (C. malabaricus stricklandii-possible separate species?) are found only in the north and nowhere else in the world.
The back yard gardener and amateur birder will get to know the Magpie-robins very quickly. They are familiar in most parts of open areas in Kuching. Our forest dwellers, the Shamas, will require waking up a bit early or wandering around 7 p.m. near the edge of the forest. Grab your binoculars and field guide and enjoy these birds that arrived from Africa many millions of years ago.