REDUCED WINGS OF BIRDS. 51 



The great principle of economy is continually at 

 work shaping organisms, as sculptors shape statues, 

 by removing the superfluous parts ; and a mere 

 glance at the forms of animals in general will 

 show that it is well-nigh as dominant and uni- 

 versal a principle as is that of the positive 

 development of useful parts. Other causes, more- 

 over besides actual economy, would favour shorter 

 and more convenient wings on oceanic islands. 

 In the first place, birds that were somewhat weak 

 on the wing would be most likely to settle on an 

 island and stay there. Shortened wings would 

 then become advantageous because they would 

 restrain fatal migratory tendencies or useless 

 and perilous flights in which the birds that flew 

 furthest would be most often carried away by 

 storms and adverse winds. Reduced wings would 

 keep the birds near the shelter and the food 

 afforded by the island and its neighbourhood, 

 and in some cases would become adapted to act 



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