Dr Stephen Davies, Adjunct Professor, Department of Environmental Biology, Curtin University and ornithologist extraordinaire, presented a talk on megapods at the DRB meeting held on 14th March.
His illustrated talk presented us with the general characteristics of the megapods (Family Megapodiidae; with a literal meaning “large footed”), with members including the scrub fowls, brush turkeys, Mallee fowl and maleo. Megapod members are characterised by their persistent feet-scratching activities and proportionately small heads.
All are ground dwelling within the Australasian and SE Asian regions, including the Nicobar Islands and as far to the east as the Tongan Islands of the Pacific. All species, except for one, are found east of the Wallace Line. The megapods comprise seven genera and 22 species of which eight are extinct. All are mound builders using external heat sources in a number of ways to incubate their eggs. Heat sources generally originate from a collected accumulation of decomposing organic debris, but geothermal sources, such as volcanically warmed sands, and direct solarisation are also utilised.
Stephen began his talk with a story of survival, that of Bruijn’s brush turkey (Aepypodius bruijnii), a little known species related to the Australian brush turkey. Discovered in 1880 and described from the evidence of traded skins only, it was found to be endemic to Waigeo Island West Papua. It was not recorded as a live specimen for more than 120 years and was considered extinct. There have been 15, low altitude, ornithological expeditions to Waigeo to establish whether it still survives but all failed. A single head discovered in 2001 indicated that the bird was not extinct. Finally in 2002 it was discovered quite unexpectedly on the mountain peaks from altitudes above 600 m to the highest summits. Little research has been conducted on the birds, but it is recorded that the male birds have the mounds, made from forest debris and light soils, and that they are polygamous.
Mound building activities of the megapods, utilising piled fallen leaves and other organic material, may have begun from natural debris accumulated within the roots of fallen trees. A short film on the mound-building activities of a pair of jungle fowls demonstrated to us the frenetic work involved in digging and dispersing soil and organic debris to heights and spreads of over several metres, often with the pair showering one another by their actions. Soil is both scratched and clutched in the digging process, with one foot used for a few scoops, then changed to the other. The large mounds are constructed to house a nest chamber that is accessed by a tube construction somewhere below the top of the mound. Adult birds test the temperature within the mound with their tongues and when that is within a suitable range (33oC for the jungle fowl) an egg is laid. Mounds have their own microenvironment, with high CO2, low O2 and high humidity and during the incubation period (60-90 days for the jungle fowl), pores within the egg’s shell open to allow gaseous exchanges. The single large egg of the jungle fowl is twice the size of that produced by the Mallee fowl. Eggs are thin shelled thus enabling the chick to get out by breaking the shell with its claws. The chick then has to dig its way out of the mound, work that may take several days. Instinctively the chick scurries away from the mound with the threat of predators being high.
The Mallee fowl (Leipoa ocellata), more familiar to WA naturalists than the jungle fowls, is larger than the jungle fowl and with its patterned plumage it is easily camouflaged. Mallee fowl are listed as vulnerable throughout Australia and their range has become progressively more restricted. There are variations in behavioural activities through Australia; in the Eastern States the male bird performs the work whilst in WA both birds of the pair perform the work of mound building.
WA has the largest population of Mallee fowl in Australia, living within the biogeographical region from the Shark Bay area to the south eastern coast and covering several known areas within a more or less triangular zone of the State. Mallee fowl territories vary in size and some contain as many as twenty mounds. Many of the mound sites are monitored by special interest conservation groups* including the WWF.
Mounds of the Mallee fowl are smaller than those of the jungle fowl. They are opened up before the winter rains so as the organic matter gets a soaking and then covered over to ferment to reach the required incubation temperature (~33oC). As well as the heat derived from fermentation of the organic debris, opening the mound also allows the summer sun to warm up it. Mallee fowl lay up to 20 eggs with intervals of 5-7 days between each egg. The newly hatched chick takes about 12 hours to climb from the inner chamber at a time just before dawn, and after a brief rest, it then travels about 600 m on its first day. Mounds are checked constantly by raptors and goannas as well as other animals. Monitoring of some chicks with specially fitted radio-transmitters demonstrates that they move around a lot. The young birds are fairly sociable and separate when the time comes to establish a territory. They mature at about 9 to 10 months.
Susan Stocklmayer
A summation of work and biography of Stephen Davies is on the following web site: http://www.australianoftheyear.org.au/honour-roll/?view=fullView&recipientID=549
Many web sites provide details on Mallee fowl interest and conservation groups in WA such as:
www.yongergnow. com.au
Reporters note. It is interesting to note the change of attitudes on environmental issues from those held in the 1930s. I own a volume of the well-known Mrs Beeton’s Cookery containing recipes for preparing baked Mallee fowl and other Australian fauna.