The Malleefowl is one of three species of mound builders, or Megapodiidae, found in Australia. The Megapodes, as they are some times referred to, are long-legged gallinaceous birds, that is, akin to domestic poultry, pheasants, etc. Megapodes are widely distributed in the Australasian region, extending to Java in the west, central Pacific in the east and to the Philippines in the north.
The birds are terrestrial and are distinguished by their habit of leaving eggs to be incubated in sand or soil heated by the sun or volcanic action or in mounds of rotting leaves built for that purpose, as Malleefowl do.
The Malleefowl is unique in that it is the only megapod that makes it's home in dry, inland scrub.
The other Australian megapods are the Orange Footed Scrub Fowl (megapodius freycinet), found in the rainforests along the northern coast of Australia (also found in Papua New Guinea and known as megapodius reinwardt), and the Brush Turkey (Alectura lathami), found along the east coast, north of central NSW.
The Malleefowl has large and powerful feet, which it uses to build enormous egg-incubating mounds. In winter an area of ground is selected, typically a small open space between the stunted trees of the mallee. Some researchers believe that the female chooses the nestsite and sometimes changes her mind. Other researchers say both birds gather material and start to prepare the nest. Yet again, others say it is just the male that makes the selection. All agree that once the nest is constructed, the male tends the nest almost exclusively, except some say that the female does the final digging around the egg-chamber when an egg is to be laid.
In any case, a depression, measuring about three metres across and just under a metre deep, is scraped in the sandy soil. An egg-chamber is constructed at the bottom of the mound. The male does this by raking backwards with his feet. In late winter and early spring he will begin to collect organic matter. Raking sticks, leaves and bark into wind-rows for up to 50 metres around the hole he will build it into the nest mound rising up to 1.2 metres above the ground level and with a diameter up to 8 metres. The amount of litter in the mound will vary. It may be mostly organic material, mostly sand, or somewhere in between.
After rain, he turns and mixes the material to encourage decay. The timing varies with temperature and rainfall.
Maintaining the Right Temperature
Throughout the breeding season the male has to ensure that the temperature inside the mound is maintained at about 33°C - 91°F. The male puts his head into the mound and it is thought that he uses his tongue to measure the temperature. He must then either add or remove sand from the mound, according to the temperature within it and the season.
In spring, much heat is given off by the rotting organic material and the temperature needs to be reduced. At dawn, the male rakes off the sand covering the litter, and after allowing enough heat to escape he refills the hole with cool sand.
In summer, the male needs to protect the eggs from the heat of the sun. He adds more and more sand to the mound, which absorbs the sun's warmth. Then, in the cool of the morning, he removes the sand and scatters it in the colder air. When the sand has cooled down he puts it back on the mound.
During the cooler temperatures of autumn, the mound needs to be warmed up. To do this the male digs almost all of the soil away in the morning, spreading it out to be warmed in the sun. Throughout the hottest part of the day, he places hot layers of sand on the mound, so that as the sun goes down the nest has been rebuilt and is warm for the night.
Laying the Eggs
While the male is keeping the temperature of the mound constant, the female is busy laying eggs and helping with the digging (although there is some contention about this latter point). Generally an egg is laid every four to eight days. The female lays about 15 to 24 eggs in a season, although that number can be as high as 32. The number varies with the availablity of food.
The eggs are large and thin shelled. Each egg weighs about 10% of the female's body weight and over the course of a season it is not uncommon for her to lay 250% of her own weight. She lays her eggs in the bottom of the mound in the egg chamber, which she has exposed for that purpose. The egg chamber is a box like structure about 40 to 50 cm cube.
Incubation time depends on temperature and can vary from between 50 and 100 days. Hatchlings use their strong feet to break out of the egg, then lie on their backs and scratch their way to the surface. They struggle hard for five to ten minutes to gain 3 to 15 cm at a time. After resting for an hour or so they start for the surface again. It takes anywhere between 2 and 15 hours for them to make it all the way out of the mound.
Chicks pop their heads out of the nesting material with their eyes and beaks tightly closed. Immediately they take a deep breath and open their eyes. They may remain motionless for as long as 20 minutes before quickly emerging from out of the hole and rolling or staggering to the base of the mound.
They quickly disappear into the scrub and within an hour they will be able to run reasonably well. Chicks can flutter for a short distance and run very fast within two hours. Despite not having yet grown tail feathers they can fly strongly within a day.
Chicks have no contact with adults or other chicks. They tend to hatch one at a time. Birds of any age tend to ignore each other except for mating or territorial disputes.