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History of Australian Dromornis Stirtoni – The heaviest bird that ever lived

Weighing half a ton (over 500 kg (1,100 1b)), Dromornis was one form of a group of giant birds (family Drotnornithidae), unique to Australia, which lived between some 15 million and 26,000 years ago, perhaps even much more recently.

Height of the bird

Dromornis Stirtoni

The Australian Dromornis stirtoni grew to half a ton on a diet of plants.

Though emu-like, they certainly were not emus and have come to be called the Mihirung birds. Some were only slightly larger than the modern emu, but stirtoni was over 3 m, almost 10 ft high.

Dromornis Stirtoni Bird Habitat

Remains from a site near Alice Springs in the Northern Territory show that Stirtoni lived alongside two much smaller forms of Dromornis and Aboriginal man.  This was in the Pliocene and Miocene epochs, between 2.5 and nine million years ago. Yet fossil birds of up to 130 million years ago are known from Australia.

During the Miocene period, central Australia must have been decidedly wetter and had a more predictable climate. It was inhabited by some very familiar forms, such as emus, ducks, pelicans, cormorants, and rails, as well as some very unfamiliar and unpredictable forms such as Dromornis and modern flamingoes.

Pollen collected from sediments of similar age in the area indicates much higher rainfall with forests of southern beech and many surrounded by lush lakes vegetation.

In such an environment there was a clear niche for grazing animals, which is what the dromornithids were. Plant material is generally of low nutritive value and needs to be ingested in bulk to yield viable energy levels. Thus generally herbivorous mammals and birds tend to be large to maximize feeding efficiency.

Physical Structure and Diet of Dromornis Stirtoni

Fossils discovered

Dromornis and the other Mihirungs had very deep lower jaws, hoof-like toe bones and a distinctly shaped bone called the quadrate connecting the upper and lower jaws. Their lack of down-curving claws and a hook on the beak also suggests that they were plant-eaters rather than carnivores. Their jaws were capable of withstanding large forces and were very unlike the slender jaws of emus and cassowaries, but their precise diet remains a mystery.

These great birds appear to have been most successful in the forest environments which characterized much of Australia for much of the Cainozoic period. But as the climate changed, the forests contracted and the grasslands expanded, the Dromornis were increasingly unable to cope with the rise and diversification of the kangaroo, which adapted superbly to new openings for grazing animals.

What dealt the final blow to the dromornithids is unknown, though a man might have had a hand in causing the eventual extinction. Five genera and eight species of dromornithids currently are recognized.

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