578 Mr. R. C. L. Perkins — Introduction to 



perfectly modified it is for obtaining these ; how perfectly 

 adapted is the bill of such a form as DrejJanorhatiiphus for ob- 

 taining the nectar from the deep tubes of the giant-blossomed 

 Lobeliacese, inaccessible to other birds ; how wonderful is 

 the form of Heterorlujnchus, which delights in the hard 

 boring weevils^ themselves equally noticeable ; how powerful 

 are the muscles of the head and beak of Chloridops, which 

 can crack the stones of the ripe fruit of the bastard sandal ; 

 the extraordinary advantage of this specialization in each 

 form for acquiring a constant supply of food almost or quite 

 inaccessible to its allies, and that too in a country where the 

 small land-area may be supposed to have rendered competition 

 unusually keen, must appeal with the greatest force. 



12. Hiffh Specialization may become a Source of great 

 Danger. 



This high degree of specialization, although of the greatest 

 benefit under stable conditions, with a change of these 

 obviously becomes a source of great danger. Thus, destroy 

 the special food- supply of the birds mentioned above, and 

 there is little doubt but that most of them would very quickly 

 become extinct ; for forms so perfectly adapted for special 

 ends are, under ordinary circumstances, but ill-adapted to 

 change their mode of life ; and it is amongst such forms 

 that most of the rarest species are found, while a consider- 

 able number of them already verge on extinction. It is 

 probable that this state of things has largely been brought 

 about by man, and in particular by the destruction of 

 the lowest forest. Even now, in winter storms, large num- 

 bers of birds resort to the lowest skirts of the existing forest, 

 generally at an elevation of 1200-1500 feet; and it is well 

 known that in Cook^s time such forms as Psittacirostra, 

 Himatione, and Chlurodrepanis actually came dowu to the 

 coast in Kealakeakua Bay, though now such flights would 

 mean death to the visitants. Moreover, at these lower alti- 

 tudes the flowering-season of most plants is different from 

 that in the uplands, and they must have been an important 

 source of food at seasons when it was scarce elsewhere. 



