Steadman Sylviornis

Scientific name: Sylviornis neocaledoniae Scientific classification: Phylum: Chordata Class: Aves Order: Galliformes Family: Sylviornithidae When did it become extinct? The du is thought to have become extinct around 1,500 years ago, but it is possible that the species survived into more recent times.

Sylviornis Skeleton
Du—The 30-kg du constructed huge nest mounds on New Caledonia and the Ile des Pins. (Renata Cunha)

Where did it live? The remains of this bird have been found in New Caledonia and the nearby island of Île des Pins.

In Australia, New Guinea, parts of Indonesia, and some of the Pacific islands live birds known by various names, including megapodes, brush-turkeys, mound builders, and incubator birds. These chicken-sized animals are unique among their feathered relatives for building large mounds, in which they incubate their eggs. The well-known malleefowl (Leipoa ocellata) of Australia scrabbles at the ground with its feet and beak to excavate a pit up to 3 m wide and 1 m deep. The male bird is actually responsible for digging, and he part fills the pit with leaf litter and other rotting vegetation before his mate lays her clutch of eggs into the waiting organic incubator. The male kicks soil into the pit and keeps on going until he has formed a big heap, which can sometimes be 0.6 m high and several meters across.

The mound of the malleefowl is quite an impressive structure for a small animal, so imagine the humps formed by a 30-kg, 1.5-m-tall extinct mound builder. On the Île des Pins, there are enormous, 4,000-year-old mounds, some 5 m tall and almost 50 m across, that were once thought to be burial mounds created by islanders. Excavations of these mounds revealed no human remains and no grave goods, leading to the theory they may have been built by a giant bird as incubator mounds. Four thousand years have passed since the mounds were first built, and in that time, the elements have probably eroded them, so they must have been considerably bigger when they were new.

Sadly, the du is not around today, and we can only guess at what this bizarre bird looked like in life. We have no idea what its closest relatives are, and it is not known if it was actually closely related to the living mound builders. With that said, it is often portrayed as a thickset animal, with a large bill and a bony lump above its eyes that was covered in a fleshy comb. Such a large, heavy bird was undoubtedly too big to take to the wing, and we can be quite confident that it was flightless like many other giant island birds. Along with what was an unusual outward appearance, the du had a number of skeletal peculiarities that set it apart from the majority of other birds. In most birds, the two collarbones are fused to form the bone that every meat eater knows: the wishbone. In birds, the wishbone strengthens the chest skeleton for the muscular forces that are generated during flapping flight. The du's collarbones were not fused. It has also been said that the rib cage and the pelvis have many similarities with those of dinosaurs.

With only fragmentary evidence available to us, we can only speculate on the way the du lived its life. The bird's skeleton does not carry any of the hallmarks of a formidable predator, so we can assume that it was probably a herbivore that may have extended its diet to include invertebrates. It may have used its powerful legs to scrape at the soil for nutritious roots and tubers, but we'll never know what food it ate and how it found it. Apart from the giant mounds on Île des Pins, the possible incubator mounds of the du, we have precious little information on the rest of its breeding behavior. Did several birds work collectively to build the huge mounds, or was each one the work of a single pair? Such large structures undoubtedly took a great deal of digging and subsequent back-filling, and the birds must have toiled day and night. It is possible that the mounds were built over time by generations of du. As these birds had given up the power of flight, New Caledonia and the Île des Pins must have been free of land predators, and therefore the mortality of the young birds must have been low. This scenario normally results in long-lived animals with very low reproductive rates, but in various places throughout these islands, there are abundant, fragmentary remains of the du, and it seems there were juvenile birds in profusion. This had led some experts to suggest that the du produced large clutches of up to 10 eggs, and if this was the case, the du's life span was probably fewer than 10 years, which is very low for such a large bird. Perhaps the birds were killed off by disease or intermittent harsh weather, forcing the populations to adapt and produce large numbers of young.

On its Pacific islands, the du probably lived a relatively peaceful existence, with no predators to worry about and only food and mating to concern its bird brain. This untroubled way of life was shattered by the arrival of humans, who reached these shores from the direction of Australia. It is thought that the first humans to reach these islands were from a diverse group of people known as the Lapita and that they probably made landfall on New Caledonia and the Île des Pins around 1500 B.c., but this date is debatable. As with other untouched islands around the world, the arrival of humans heralded death and destruction for the original inhabitants. A large, flightless bird like the du, with no innate fear of humans, was easy pickings, and its flesh would have been a welcome treat for seafarers who had probably eked out a survival on meager rations for many months. The nest mounds, with their sizeable clutches of big eggs, would also have been vulnerable to humans and their collected menagerie (dogs, pigs, rats, etc.), and nest raids hastened the decline of the du. It is thought that humans managed to wipe out the du about 1,500 years ago.

♦ It has been suggested that the du may have survived into more recent times as giant birds exist in the folklore of the present inhabitants of New Caledonia and the Île des Pins.

♦ New Zealand, New Caledonia, the Île des Pins, and surrounding islands in the western Pacific are the only visible parts of a great, submerged continent known as Zealandia, a landmass with an area greater than Greenland or India. Zealandia sank beneath the waves around 23 million years ago. It once formed part of the giant landmass known as Gondwanaland, but all that we can see today are its highest reaches.

♦ The flora and fauna of New Caledonia are very special. Many of the plants and animals are endemic and relics of the flora and fauna that populated the now fragmented Gondwanaland. As there were no native New Caledonian mammals, the fauna was dominated by birds and reptiles, but along with the du, many of the other, large denizens of this unique place are sadly extinct.

Further Reading: Poplin, F., and C. Mourer-Chauviré. "Sylviornis neocaledoniae (Aves, Galliformes, Megapodiidae), oiseau Géant éteint de l'ile des Pins (Nouvelle-Calédonie)." Geobios 18 (1985): 73-105; Steadman, D. W. "Extinction of Birds in Eastern Polynesia: A Review of the Record, and Comparisons with Other Pacific Island Groups." Journal of Archaeological Science 16 (1989): 177-205.

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