Orange, red or yellow? The varying colours of the Flameback woodpecker subspecies have been confusing biologists for years. Now, a study by Sri Lankan scientists seems to have got to the bottom of the mystery. Neha Sinha clues us in on this latest evolutionary revelation.
Photo: Vimukthi Weerathunga.
Flameback! The name itself is wildly colourful, suggesting vivid oil pastels on textured paper, or a little splash of colour with an accompanying riff of music. Flamebacks, a woodpecker species, are not modest birds. They sound like carpenters at work, knocking about on wood, and they look like carnival splotches of colour against old tree trunks. Yet, the Ivory-billed Woodpecker is an icon of extinction, a bird that was lost in the United States almost before it was appreciated, and we still know little about flamebacks.
For me, woodpeckers are fascinating because of their hardiness. Watching a little bird, tapping away at a hard tree many times its own size, armed with nothing but a sturdy beak, a hard cranium, and persistence – is like witnessing a physical triumph for all little creatures of the woods. Woodpeckers have unique, barbed, flicking tongues, which they use expertly to spear insects from the whittled wood their hard beaks carve off. The holes created are used by other birds as well, so in a sense, woodpeckers are architects of the forest ecosystem. Birders have observed that woodpeckers whittle wood in spirals, covering the largest possible space in a small period of time. In children’s books, woodpeckers are represented as the suited-and-booted ‘doctors’ of trees, ridding them of arboreal infestations. And if you hear a woodpecker at work in a forest, you know that the forest is in good health. In the forests of Sri Lanka, a group of researchers, fascinated by the species, went about solving some visually-flaming woodpecker mysteries.
Dinopium benghalense is commonly known as the Black-rumped Flameback or Lesser Goldenback in India. The idea behind the study was to understand why flamebacks show such vivid plumage colouration as well as vivid differences in colours – particularly between subspecies of flamebacks found in northern Sri Lanka Dinopium benghalense puncticolle (found closer to India) and the endemic species Dinopium benghalense psarodus found southwards on the island. The subspecies in north Sri Lanka and in India is referred to as the Golden-backed Woodpecker – the bird is an eye-popping shade of yellow. But, the subspecies of flameback found toward the southern part of Sri Lanka has a red back.
Says Saminda Fernando of the Department of Zoology, University of Colombo, “Flamebacks are fascinating birds; they have unique characteristics. They are builders in a way, building holes in trees. They are more or less difficult to spot, as they are found high up on trees such as tall coconut trees. The holes they make are used by other species as well.”
Photo: Vimukthi Weerathunga.
A CLOSER LOOK
To properly examine the birds, they needed to be caught and their genetic samples procured. This was done using two brightly-coloured decoy birds, each constructed to resemble a male woodpecker in two distinct colours. Playback of flameback calls was also used, as was a mist net; and most importantly, the team invested patience and gentleness. The decoy was a male, because as the team charmingly put it, female birds would be attracted to the males, and males would fly in to drive the competitor away. Recordings of the bird’s call – the rattling ‘kiri kiri kiri’ sound - proved effective in combination with the mist nets. Once the birds were caught, their feathers were gently stretched out to extract a few drops of blood, exactly 50 microlitres, with a sterilised needle.
In a 4X4 Gypsy, halting regularly at numerous field camps, the Colombo team, headed by Dr. Sampath Seneviratne from the University of Colombo, drove along a line transect of 470 km. from Jaffna to Matara. Morphometric data was also collected: head length, head width, culmen (upper ridge of the beak), bill width, bill height, flat wing length and 1st claw length for 70 birds. Genetic material (a tiny droplet of blood) was taken from 16 birds, and a mitochondrial gene test and sex (Z) chromosome test was carried out.
DARWIN’S RIGHT AGAIN!
The conclusions arrived at are astonishing, and read like a short history of evolution aided by isolation. The species of Yellow/Golden-backed Flamebacks found in India are the same as those found in northern Sri Lanka. But with increasing distance from India, and a change in biogeographic and rainfall gradient, the flamebacks began changing colour. The endemic Sri Lankan Flameback is red, not yellow. What’s more, mating between subspecies seems to have created the colour you would get if you mixed yellow and red on a palette: an unabashedly orange flameback. Saminda opines that, “The birds found in northern Sri Lanka are yellow, like the Indian Lesser Flameback. But southwards in Sri Lanka, the flameback is a vivid red, and not yellow. Intermediate birds, produced by mating between the red and yellow varieties, are orange or orange-red in colour.”
He adds: “It appears that distance from India is a barrier that influences gene flow. It also appears that the rainfall gradient is a barrier. These barriers have provided isolation for the Sri Lankan endemic, leading to reproductive isolation. The gene tests show that the ‘hybrid’ birds are offspring of yellow (Golden-backed) fathers and red (Red-backed) mothers, or vice versa.
In other words, differences in climate and physical habitats are triggers for speciation. For instance, the red variety of flameback is found south of the Sri Lankan city of Anuradhapura and nowhere else in the world.
Photo: Saminda Fernando.
When we consider birds and how they have shaped our lives, their colours and characteristics come to mind. For urban dwellers, Rufous Tree-pies are a welcome rinse of colour, while Magpie Robins charm with their clear clarion calls, and chatty demeanour. Perhaps we may not actually pause to think about why and how these birds evolved the way they did: how, for example, do Indonesian Birds of Paradise manage the long tails they have, and what are the evolutionary reasons for them possessing such luminescent, jaw-dropping plumage? And will woodpeckers drilling on different kinds of wood have different beaks? Why are certain species found where they are, for instance, why are ostriches not found in Delhi? We may never know the precise processes of evolution, but we can try to guess at some of nature’s mysteries. Climate certainly influences the coats, hues and tools that animals have.
Try to puzzle this one out. In the course of this research, differences in beak length between Indian and Sri Lankan flamebacks were recorded. The beaks of Sri Lankan endemics are several milimetres longer than their Indian counterparts! The Red endemics’ average beak length is 39 mm., while the beaks of the yellow variations from north Sri Lanka are 35 mm. long. What could be a determinant for this? Perhaps the answer lies in rainfall. Northern Sri Lanka receives about 1,200 mm. of rainfall annually, while southern Sri Lanka is much wetter, with an annual mean rainfall of over 3,000 mm. While there are no confirmed answers for the ‘why’s’ of speciation, one reason could be that higher rainfall leads to wetter wood in trees. The researchers conjecture that wetter places have larger trees, and a longer beak might offer some yet unknown advantage in chiselling holes.
The ruthlessly efficient beaks are also a factor to be dealt with while catching the birds. Saminda has permanent marks on his hands, as he and his colleagues were ‘drilled’ at by the flamebacks that they caught. People are scared of the flameback’s sawing and rattling ‘kiri kiri’ call. But it’s really their beaks, and not their calls, that are formidable, he quips. There are more, real dangers that researchers must contend with. At the Wilpattu National Park, the team encountered a strange sound. Within minutes, a sloth bear appeared. It was moving its head from side to side so it did not seem to spot the team, and luckily there was no untoward incident.
Saminda and Sampath’s work was presented at the Student Conference on Conservation Science in Bangalore, India. The conference, with an emphasis on original research from Asia and Africa, had several papers that join the dots between Indian species and their neighbours. In the most basic sense, their findings show the relevance of micro-habitats and how they could potentially impact speciation. A difference in gradient of rainfall changes tree wood, and in the process, also changes beaks. To preserve diversity in species, we absolutely have to preserve habitats. If we homogenise habitats, we lose diversity.
When I travel to different states in India – or different countries – I am struck by how behavioural ecology of species changes in different places. Rocks, rainfall, forests, grasslands, and plant communities all play a role in how creatures look and behave. Different places mould what we see and hear; varied habitats throw up unique bird and animal sightings, and a variety of bird song and background sounds.
Photo: Saminda Fernando.
I, for one, celebrate such diversity. Imagine if all habitats were cut in the same mould! The world would surely be a drab, drab place, robbing us of the chance of seeing the flamebacks’ sartorial red, yellow and orange styles.
To catch the flameback, a colourful decoy was made. Two versions: one with a bright yellow back, and one with a bright red back, were set up. A black cord was tied to the dummy and yanked to show movements. Calls of the flameback were played. A mist net was set up. Dip nets were also used. The result: females came to check-out the ‘new guy’, and males came to fight off the ‘competitor’! Once caught, morphometric, blood and feather samples were quickly taken from the captured birds. Birds were ringed before release.
First appeared in: Sanctuary Asia, Vol. XXXIV No. 6, December 2014.