of living flightless birds, and birds that are well on the way to 
this condition, will afford us a ready answer. 
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 year 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. 
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