The Moluccan Scrubfowl
by Dr C.J. Heij and Dr Christny F.E. Rompas, from OBC Bulletin 25, June 1997.
Worldwide there are 22 species of Scrubfowl, found in Papua New Guinea, Australia, Indonesia, the Philippines, the Nicobar Islands and the south-west Pacific. Scrubfowl are the only birds which do not brood their eggs using body heat. Some species use the heat of the sun for incubation, others use volcanic heat or the heat generated by rotting vegetation. Most Scrubfowl are mound builders, building enormous hills which can have a diameter of up to 10m and be 1-2m high. The internal temperature of the mound is regulated by adding, moving or removing sand and vegetation and digging holes. Uniquely, the Moluccan Scrubfowl, Eulipoa wallacei, just digs a hole, throws sand over the egg, then flies off, not even returning to check or regulate the incubation temperature.
During Scrubfowl evolution several special adaptations have occurred to allow for this type of incubation. The eggs are very large and contain almost entirely yolk and have a very thin shell. The embryos have an egg tooth but this is lost before they hatch. The egg is also without an air chamber. The first breath is taken as soon as the shell is broken when the hatchling pushes itself out of the shell and digs its way to the surface. It is not in any hurry, because it still contains a large store of yolk and fat.
Scrubfowl with their strange adaptations are fascinating from an evolutionary point of view. There is a theory that the birds first utilised piles of rotting leaves and holes in rotting trees to incubate their eggs then gradually evolved towards using volcanically warmed ground and warm beaches. Their reproductive strategy can be looked upon as being rather primitive and reptilian but they can also be regarded as progressive, a refinement on birds who sit on nests. However, the birds leave a beach full of holes and a clear indication of where the eggs have been laid: a larder which must and does attract predators like snakes, monitors, cats, pigs, feral dogs and rats. Birds of prey, such as the Brahminy Kite, Haliastur indus, also await the young as they struggle out of the sand and take a heavy toll of freshly emerged chicks.
In June 1994 we arrived in the small Islamic village of Kailolo on the unspoilt island of Haruku, in order to spend more than a year researching the Moluccan Scrubfowl. Together with Galele (NE Halmahera) Haruku is probably the last big breeding colony of this species in the world.
The Moluccan Scrubfowl lives in the impenetrable tropical rainforest on the mountain slopes of Haruku and the surrounding islands. Little is known about its breeding behaviour and the literature only mentions occasional incidental observations of the bird in its natural habitat. On Haruku we tried to gather as much information as possible on this unique bird, about which so little is known. We hoped that this knowledge might be of help to enable us to re-introduce the Moluccan Scrubfowl to areas where it has disappeared.
Nesting grounds are found about 100m in from the coast and there were five such areas in our study site. When a female is ready to lay she makes a night flight to her laying place, usually a warm beach by day, sometimes having to cross the sea to reach it. Exactly where these birds come from is not exactly known. Once she arrives at the site she rests in the crown of a tree looking for a suitable place to lay.
At night, preferably around the time of the full moon, she digs a hole nearly a metre deep, lays a single large salmon-coloured egg in the hole, and covers it up and leaves it to fate. The egg contains mainly yolk and is hatched by the heat of the sun. The eggs weigh an average of 103g, (which is very heavy considering that the adult bird only weighs about 500g i.e. about 20% of body weight), and resemble goose eggs. When the eggs hatch the chicks dig their way to the surface and immediately scurry into the forest. They are completely developed and independent: the Scrubfowl does not ‘parent’ its young in any way. Exactly where the young go after hatching is not known.
Each year the village chief of Kailolo puts the rights to search in a particular area up for auction and the successful candidate employs villagers to guard and excavate the eggs. Some of the eggs are for personal consumption and the rest are sold, providing a small income for the villagers. There is also a small income from the eco-tourists who visit the nesting grounds each year. During the dry monsoon, as many as 200 eggs a day can be collected by local villagers, a process which inevitably also uncovers young chicks. Although it is very difficult to re-bury any chicks accidentally dug up in the search for eggs, this is the chick’s only chance for survival. Once collected the eggs are cooked by local villagers, the flavour being reminiscent of goose eggs.
When I asked the winner of the auction whether he would earn enough money from selling eggs one year, he replied that the higher the price, the more eggs the birds lay. Asked if the birds would not be angry at having to lay ever more eggs, he answered that it is Allah’s responsibility to ensure that the birds would lay more and that Allah would help him since 75% of his proceeds go to the local Mosque.
In addition to observation of the nesting grounds and investigation of the egg harvesting, I also searched for other nesting places on Haruku and other Moluccan islands, including Seram, Halmahera and Buru. The Moluccan Scrubfowl has now become so scarce that mapping its exact present habitat and range is of great importance in conserving the species. Its disappearance in other parts of the Moluccas is a serious problem. Cutting down of the rainforest and new settlers who know nothing about sustainable harvesting from the forest are the major threats facing these birds. The eggs have been over-collected, without any restrictions being imposed, and the birds themselves are shot for food.
Throughout the study Dr Heij was working with the cooperation of staff at the University of Bogor.