Whenever we find birds living, so to speak, lives of languorous 

 ease — where there are no enemies to be evaded, where there is an 

 abundance of food to be picked up on the ground all the vear 

 round, and the climate is kindly, there flight is no longer practised. 

 Year by year, generation after generation passes by, and no use 

 whatever is made of the wings. In all such cases these once most 

 vital organs dwindle away, and finally vanish. We can trace 

 every step in this process of decay. 



We may begin with the " steamer-duck " of the Falklands. 

 In this species, after the first moult, the power of flight is lost for 

 ever. Among living birds only a few species, apart from the 

 ostrich-tribe, are in this dolorous case. The owl-parrot, or kakapo, 

 of New Zealand, is one of these. A grebe found only on Lake 

 Titacaca, perched high up a mountain-side is another. In both 

 these birds the keel of the sternum is represented by the merest 

 vestige, the breast-bone being reduced to the condition found in 

 the ostrich-tribe. 



The two giant pigeons, the dodo, and its cousin the solitaire, 

 afford instances where the loss of flight has been followed by 

 extinction ; owing to the invasion of their haunts, through the 

 agency of man, by pigs and other domesticated animals, which 

 destroyed their eggs and young. 



The ostrich-tribe is peculiarly interesting : owing to the fact that 

 their wings present a really wonderful series of degenerating stages. 



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