Although clearly gallinaceous in structure, the Megapodes stand out boldly from all known birds in a number of marked peculiarities. They are the only birds known to depend wholly on artificial incubation for their eggs, thus being, as Dr. Stejneger has said, ” the first feathered inventors of an artificial incubator to take the place of the mother and provide the warmth necessary to develop the embryo contained in the eggs into a perfect chick, which is ordinarily supplied by the parent’s body.” They are also the only birds known in which the young are hatched fully feathered and able to fly from birth.
The Megapodes are mostly plain, dark-colored birds, approximating in size the common fowl, although some, as the Brush Turkey, are as large as a hen Turkey. They have very large legs and feet, with long, curved claws, and have the first toe on the same level as the others. They are found in Australia, New Guinea, and the Philippines, and are usually met with in pairs or small parties, although the species in the Nicobar Islands (Megapodius nicobariensis) is often found in flocks of from thirty to fifty. They remain in the vicinity of the sea-shore or along streams, frequenting the dense brush, where they live on a variety of things, as roots, fallen fruit, insects, worms, snails, and centipedes. The flesh, however, is white and well flavored. They are rather difficult to observe, as they run swiftly when alarmed; when flushed they fly heavily and with much noise.
The Megapodes, of which seven genera and about thirty species have been described, first attracted attention more than three hundred years ago, when one of the survivors of Magellan’s voyage mentioned the curious nesting habits of the Philippine species. Soon other observations were added to this, and nesting habits that at first seemed impossible came to be authenticated.
In the manner of the preparation of these curious artificial incubators the Megapodes may be divided into two groups, the so-called Mound-builders and the Maleos. In the first group the birds scratch or kick together great mounds of rubbish, consisting of dirt, grass, leaves, and rotten wood, in the midst of which they deposit their eggs. The mounds differ greatly in size, some being only a few feet across, while others may be ten, fifteen, or thirty feet across, and often six feet high, and one of extraordinary size, described from the island of Nogo, was one hundred and fifty feet in circumference. They are usually of conical shape, although some have been seen in the form of a long bank, nearly thirty feet in length, and more than five feet in height. It appears that both males and females work in the construction of these mounds, which are begun some weeks previous to the period of laying, in the case of new ones, although they are often used from year to year by simply adding more material. While the evidence is somewhat conflicting, it appears beyond doubt that in some of the species at least several pairs take part in the building and jointly occupy the mound, as a considerable number of eggs have been taken from a single mound. Other observers insist that only one pair occupy a mound.
The eggs are of enormous size, considering the size of the bird, being from three to three and a quarter inches long and from two to two and a quarter inches in short diameter. They appear to be deposited at long intervals, as Davidson dissected a Megapode that had just laid an egg and found that the largest egg in the ovary was only the size of a large pea.
According to Wallace, the interval is some twelve or thirteen days. The number laid by a single female is unknown, but appears to range from four to eight. The egg is deposited at night and the male is said to scratch the hole in the mound for its recep tion. The hole usually runs obliquely and the egg is placed in the bottom, often nearer to the side of the mound than the top; the depth varies from four to six feet. The egg is covered with the decaying vegetable matter and left to be hatched, and how the chick can get out is a mystery, but get out it does, and runs off into the forest, where it is able to look out for itself from the first.
Of the true Megapodes (Megapodius), seventeen species have been described, among them being two species that are fairly well known, namely, the Philippine Megapode (M. Cumingi) and the nearly related Sangi Island Megapode (M. sanghirensis). Slightly different is Wallace’s Megapode (Eulipoa wallacei) of the Molucca Islands and the Ocellated Megapode (Lipoa Ocellata) of western and southern Australia. Of the true Brush Turkeys (Talegallus) four species, all of New Guinea and neighboring islands, have been described, with four allied forms (Catheturus and Aepypodius) from Australia and New Guinea.
The only remaining form is the Maleo (Megacephalon maleo) of the Celebes and Sangi islands, which differs in structure and in habits from the others. It does not build a mound, but deposits its eggs in holes in the hot sand along the seashore. The following account is given by Wallace : ” It is in loose, hot, black sand that the Maleos deposit their eggs. In the months of August and September, when there is little or no rain, they come down in pairs from the interior to this or one or two other favorite spots, and scratch holes three or four feet deep, just above high-water mark, where the female deposits a single large egg, which she covers over with about a foot of sand, and then returns to the forest. At the end of ten or twelve days she comes again to the same spot to lay another egg, and each female is supposed to lay six or eight eggs during the season. The male assists the female in making the hole, coming down and returning with her. The appearance of the bird when walking on the beach is very handsome. The glossy black and rosy white of the plumage, the helmeted head and elevated tail, like that of the common fowl, give a striking character. . . . Many birds lay in the same hole, for a dozen eggs are often found together, and these are so large that it is not possible for the body of the bird to contain more than one fully developed egg at the same time. After the eggs are deposited in the sand they are no further cared for by the mother. The young birds on breaking the shell work their way up through the sand and run off at once to the forest. Considering the great distances the birds come to deposit the eggs in a proper situation (often ten or fifteen miles), it seems extraordinary that they should take no further care of them. It is, however, quite certain that they neither do nor can watch them.”
That the nesting habits of the Megapodes are admirably adapted to the present structure and life of the birds is beyond question; but how these habits could have originated in the first place is difficult to understand. Under present conditions, if the birds were required to incubate their eggs, serious difficulties would arise. With an interval of ten or twelve days between the laying of each egg, a period of some two or three months would elapse between the first and last egg. If the eggs were left until the last was laid, the first ones would be subjected to climatic injuries as well as destruction by predatory animals; while if the female began incubation with the laying of the first egg, it would require her to remain sitting for three months, which would be impossible. It has been suggested that these nesting habits may be the survival of a habit enjoyed by a remote reptilian ancestor, but this is too improbable. Others have suggested that it arose by the birds covering up and concealing their eggs, which seems not unreasonable; yet if this be true, it is difficult to see how they could have become developed to the point where the young can fly from the time of exit from the shell!