HAWAIIAN BIRDS. 15 



prominent of which are the iiwi and akakani, will long survive, 

 since they are to no small extent insectivorous already, and 

 could doubtless become exclusively so without injury. In a 

 sharp struggle for existence, their chance for survival as against 

 some of the more specialized forms would be excellent. 



At least one Hawaiian bird is intensely local in disposition, 

 but, despite its fondness for one locality, it has become very 

 numerous, and is widely dispersed on several islands. This is 

 the omao (Phceornis). This bird has adopted food habits 

 which have subjected it to little or no competition. A confirmed 

 berry-eater, it finds food everywhere abundant in the dense 

 forest and in great variety. 



If, as the result of localization, inbreeding produces any ill 

 effects upon the vitality of Ph/vornis, they would seem to be 

 more than counterbalanced by abundant food and the absence 

 of competition. It is to be remarked, however, as having an 

 evident bearing upon its probable future fate, that Phceornis de- 

 clines to live in any but dense and undisturbed forest tracts, and 

 many years ago became extinct upon the island of Oahu. 



Allusion has been made above to the possibility of an inter- 

 change of avian strains by the passage of birds from one island 

 to the other, and a few words on the subject may be added. 



It is. a surprising and remarkable fact that channels varying 

 from only ten to thirty miles in width should prove all but im- 

 passible barriers even to small birds, to say nothing of those 

 the size and stength of a large hawk. It is at once evident that 

 if such channels actually prove barriers to the passage of birds, 

 the cause Hes in the disposition of the birds and not in the 

 physical obstacles. 



That these narrow inter-island channels have not always 

 proved impassible to birds is conclusively shown by the fact that 

 several of the genera are represented on all the islands of the main 

 group by the same species (Vestiaria and Himatione) , and that 

 several others are represented by such nearly related species 

 that the latter could have originated only from a common 

 stock. 



Having once entered and become established on an island. 



