Posts from 2011

Halmahera and the Bird of Paradise

9 December 2011

Situated midway between Sulawesi and New Guinea in the tropical marine waters of the Coral Triangle, lies the curious and enigmatic island Halmahera. Although having a similar geology to larger neighbor Sulawesi, being composed of four sinuous peninsulas each with their own distinctive volcanic, karst, and ultramafic rocks, Halmahera is astonishing in terms of its biological uniqueness. At about 18,000 sq km, it is the largest island of the Moluccas (or ‘Spice Islands’), and its rugged and remote interior is still extensively covered with rainforest.

The 19th Century naturalist Alfred Russel Wallace, who spent the better part of a decade traversing the Indonesian archipelago, visited Halmahera (then more commonly referred to as ‘Gilolo’) in 1857-1858 and recognized the island as a complete unknown in terms of its flora and fauna. Whilst basing himself on the nearby volcanic island of Ternate, Wallace made numerous forays onto the mainland and other offshore islands to collect specimens of insects and birds, many of which he noted were completely new to science. One such find was a remarkable new bird of paradise which Wallace considered one of his greatest discoveries and later came to bear his name. It was also here on Halmahera in 1858, that Wallace formulated his own theory of natural selection, independently from Charles Darwin, whilst suffering from a feverish delirium brought on by malaria.

Although not as biodiverse as the Sunda islands or New Guinea, in part due to its smaller size and distance from the mainlands of Southeast Asia and Australia, Halmahera (inclusive of several of its near offshore islands such as Morotai and Bacan) is a veritable hotspot for species endemism. Some notable animal specialties include the Ornate Cuscus (Phalanger ornatus), Sailfin Lizard (Hydrosaurus weberi), and Tri-colored Monitor (Varanus yuwonoi), among many others. But it is the wonderful array of endemic birds for which the island is particularly known, and visiting naturalists often seek out such beauties as the Ivory-breasted Pitta (Pitta maxima), White Cockatoo (Cacatua alba), Invisible Rail (Harbroptila wallacii), and the remarkable Wallace’s Standardwing (Semioptera wallacii).

Gekko vittatus

My time on Halmahera was focused in the Weda Bay region, just below the eastern peninsula, where the clear reef-filled waters are backed by undulating forested hills rising to nearly 1000 meters in elevation. Weda Bay Resort, located on the coast about a dozen kilometers north of the town, kindly hosted me during my visit and provided invaluable support for my field work. This eco-resort consists of a modest set of traditionally-built bungalows primarily catering to divers who come to enjoy the renowned marine life of the bay.

Here I spent several weeks in and out of the jungle and along disused logging roads attempting to discover the island’s many biological treasures. Whilst mammals were scarce (and almost entirely nocturnal), birdlife was incredibly rich and the air was perpetually filled with the harsh piercing calls of cockatoos, parrots, and hornbills. The forests of Halmahera are devoid of any large mammalian carnivores, with the only significant large land predators being snakes. My field assistant Lius, a native of north Halmahera, related to me a personal account of an encounter with a 9-meter Reticulated Python (Python reticulatus) which had killed and swallowed one of his companions in 1977. During my visit the only python we encountered was a Halmahera Scrub Python (Morelia tracyae) consuming a Nicobar Pigeon (Caloenas nicobarica) high in a tree.

Traditional hunting practices in this area appeared to have kept most wildlife fairly shy, and it took considerable effort to observe some species at close range. One of my most sought-after subjects was the legendary Wallace’s Standardwing (pictured below), which until as recently as the 1980’s had been seen only a handful of times in the wild. Like many other birds of paradise, the males of this species own extravagantly ornate plumage and gather at communal display grounds (leks) to compete for the attention of females. To observe the Standardwings at such a site it is necessary to arrive well before dawn, as their display activities begin just before sunrise.

Semioptera wallacii

I will never forget the first morning I spent at a Standardwing lek watching these avian acrobats and listening to their raucous calling. Within the confines of a single small tree crown several male birds had partitioned certain branches as their personal display territories, with younger or less dominant males nearby in other trees. Upon the approach of a female bird, the males would begin their frantic actions, calling loudly and putting on an incredible display which consisted raising four long white plumes on their shoulders and simultaneously expanding brilliant metallic blue breast shields whilst lightly fluttering their outstretched wings. Occasionally a bird would fly straight up several meters and slowly parachute back down to his chosen branch. The visiting female would take her time to select the male she was most impressed with, mate with him and then disappear off into the forest. I found that photographing in the dim pre-dawn light was exceptionally difficult, and not long after the sun had risen all the birds usually dispersed for their daily foraging activities.

I spent nearly a week camped in the rainforest near this site and I never tired of watching these marvelous birds. In the past few decades, many of the known lek locations have been destroyed by logging, and although I could frequently hear the sound of chainsaws in the distance, it was a relief to know that this site had been privately purchased by Weda Resort in order to preserve it.

To view photos taken during my November 2011 trip to Halmahera, click here.

References:

Coates, B.J. & K.D. Bishop (1997) A Guide to the Birds of Wallacea. Dove Publications.

Setiadi, M.I., A. Hamidy, Z. Abidin, D. Susanto, R.M. Brown, A.T. Peterson, X. Li & B.J. Evans (2009) Genetic Structure of Herpetofauna on Halmahera Island, Indonesia: Implications for Aketajawe-Lolobata National Park. Conservation Biology, 24:2, 553–562.

Wallace, A.R. (1869) The Malay Archipelago. Oxford University Press, Kuala Lumpur.

Nepenthes rajah and the Summit Rat

15 June 2011

Nepenthes rajah and Rattus baluensis

In late 2010 I was fortunate to be able to join a team of researchers investigating animal interactions with the giant pitcher plant Nepenthes rajah. Endemic to the cool and mist-shrouded slopes of Mount Kinabalu and Mount Tambuyuon in northern Borneo, this is not only one of the world’s largest Nepenthes but also the source of the original stories of “rat-eating” carnivorous plants. There exist a number of confirmed incidents of this plant consuming small mammals which are unfortunate enough to fall within the voluminous pitchers. Recent research however, has shed light on a far more interesting and complex animal/plant relationship, and prior to our 2010 work it had been already shown that the Mountain Treeshrew (Tupaia montana) visits the pitchers of N. rajah (as well as several other Bornean Nepenthes) to feed on the sweet nectar exuding from beneath the pitcher lid. The plant benefits from these visits by frequently collecting the treeshrew’s scat which fall inside the pitcher and are a valuable source of nutrients.

During the field work it was observed that some of the animal droppings found on and in the pitchers appeared different than those left behind by the Mountain Treeshrew. However, despite many days of watching the plants during daylight hours, treeshrews were the only mammals seen to visit the plants. It wasn’t until camera equipment was left in place to monitor the plants during the night that we ascertained the presence of another animal, the Summit Rat (Rattus baluensis) at the pitchers. This is the first instance confirming a rodent/Nepenthes relationship, and it is presumed that it matches the treeshrew/Nepenthes mutualism albeit nocturnally. The photo here, the first ever to illustrate this interaction, shows an image I obtained at night by use of an infrared camera trap positioned adjacent to the pitcher and illuminated by multiple strobes.

Unlike the related Nepenthes lowii, another Bornean pitcher plant which has lost its means to trap insects and depends entirely on the treeshrew droppings for its nutrients, N. rajah retains its carnivorous apparati, a slippery peristome and smooth pitcher walls, and still consumes prey. It is quite likely that the records of rats and treeshrews having drowned in N. rajah pitchers were not instances of these mammals seeking out a source of water (as has been assumed in the past), but rather the result of unfortunate animals falling into their “toilet”.

References:

Chin, L.J., J.A. Moran, C. Clarke (2010) Trap geometry in three giant montane pitcher plant species from Borneo is a function of tree shrew body size. New Phytologist 186: 461–470.

Clarke, C.M., U. Bauer, C.C. Lee, A.A. Tuen, K. Rembold (2009) Tree shrew lavatories: a novel nitrogen sequestration strategy in a tropical pitcher plant. Biology Letters 5: 632–635.

Greenwood, M., C. Clarke, C.C. Lee, A. Gunsalam & R.H. Clarke (2011) A Unique Resource Mutualism between the Giant Bornean Pitcher Plant, Nepenthes rajah, and Members of a Small Mammal Community. PLoS ONE 6:6.

New Species: Bornean Banded Pitta

12 April 2011

On the basis of recent research, the now endemic Bornean Banded Pitta (Pitta schwaneri) has been taxonomically separated as a distinct species from the Malayan Banded Pitta (P. irena) and the Javan Banded Pitta (P. guajana). The birds differ significantly and consistently in the plumage of both males and females as well as in their habitat preferences.

Bornean Banded Pitta

This is yet another example in a recent trend in splitting island endemics, with a similar story following the Sunda Clouded Leopard (Neofelis diardi) and the Bornean Pygmy Elephant (Elephas maximus borneensis), both closely related to mainland species. Exactly where to draw the line will always be a matter of subjective debate among taxonomists, but as more evidence, particularly DNA sequencing, becomes available for comparative analysis, it is likely that we will see many more species separated as distinct.

References:

Rheindt, F. E. & Eaton, J. A. 2010. “Biological species limits in the Banded Pitta Pitta guajana“. Forktail 26:86-91.


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