Birds | Australia

The cassowary is one of the heirs of the gigantic birds which inhabited the jungles of Gondwana. 

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The story of the inhabitants of this Terra Australis can be traced back to the distant days when all the continents of the southern hemisphere were one. The world was then a warmer, and more humid place, in which enormous dinosaurs ruled over a zoology in permanent evolution. The remains of that universal jungle can still be seen in the north east of Australia, and are now home to the descendents of the long extinct dinosaurs. 

The birds are the most numerous species in this green, suffocatingly humid world.  Their ability to fly meant they were not condemned to isolation like the land creatures of Australia, and competition with the species from the rest of the world produced new types of bird, which then came to these Jurassic forests, and stayed forever.
Here, there were no large predators, and food was plentiful, so many species of birds became part of the history of this independent evolution, giving rise to extraordinary creatures.

The cassowary is one of the heirs of the gigantic birds which inhabited the jungles of Gondwana.  Those common ancestors evolved into the ostriches in Africa, the rheas in South America, and the emus and cassowaries in Oceania. 
The common cassowary measures almost two metres, and weighs around sixty kilos.  A giant in terms of present-day birds, but a mere lightweight when compared to its close relative, the moas.  Both moas and cassowaries were descended from a common ancestor, and the moas inhabited New Zealand until the arrival of the Maoris, in 1350.  They measured almost four metres, and weighed two hundred and fifty kilos.  But even they had a bigger brother, the elephant bird, weighing five hundred kilos.  Yet another of the children of Gondwana, when the supercontinent split apart, it survived only in Madagascar, and eventually died out.

Despite its appearance, the cassowary is a relatively recent bird.  It is believed that it only separated from its primitive ancestor around ten thousand years ago.  On the other hand, other, more normal-looking birds are among the oldest inhabitants of these Australian jungles: the mound-builders, a group of birds which were the first to become separated from the main branch of ornithological evolution. 

The Australian brush-turkey is the most representative example of the Australian mound builders.  The males build nests which can be up to a metre high, by collecting together up to four tonnes of vegetable material.  Tiny fungi live among the dead leaves, decomposing them, and releasing heat as they breathe.  In this way, the nest becomes a gigantic incubator.  In it, a number of females lay their eggs, and the male will look after them, making sure that the temperature of the nest remains constant. 
t is believed that, somewhere on their tongues or beaks, the brush turkeys must have areas which are extremely sensitive to heat, and so during incubation, they plunge their heads down into the leaves, and check that the temperature remains between thirty and thirty five degrees centigrade.  This system, which we might think is a recent, original innovation, is in fact the demonstration accepted by many scientists as proof of just how closely the mound builders are, in evolutionary terms, to the reptiles.  For only reptiles, and the group of the brush turkeys, use this particular, and effective, system of incubation..

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