336 NATURAL HISTORY OF HAWAII. 



finds forest conditions that are suitable to its liabits over only a very limited 

 portion of the mountain area of the island. While it is an active, energetic 

 bird, it has apparently never attempted to cross the channels to the nearby 

 island of ^laui. For a hundred years at least it has l)een a rare bird on ^lolo- 

 kai, so rare, indeed, that in 1907 the writer secured l)ut three specimens as a 

 reward for seven weeks spent in the mountains in a search devoted to locating 

 this interesting and curious species. 



Still another interesing example of limited distribution among Hawaiian 

 birds is that of the nene or Hawaiian goose, which is confined to the Island of 

 Hawaii, where it leads a life of seclusion, high up on the mountainside, seldom 

 if ever descending to the sea level. The Hawaiian duck is more Avidely dis- 

 tributed, having occurred in considerable numbers on all islands of the group. 

 Unfortunately, since the introduction of the mongoose it has been quite rare 

 except on Kauai, where the mongoose has never been liberated. 



A Native Hawk and Owl. 



The Hawaiian hawk or io^^ occurs only on Hawaii, where it is still fairly 

 common. The Hawaiian owl ^'^ occurs on all the large islands. It is quite 

 closely related to the short-eared owl, common on the American continent. 

 Since it differs from the American species only in minor details, it is re- 

 garded as an island form of that species which has been reduced in size through 

 isolation. Like the coot and mud-hen. it is one of the more recent arrivals that 

 have made the islands their h(mie long enough to allow the principles of evolu- 

 tion, especially those involved in isolation, to produce slight, though easily 

 recognizable, changes in the appearance of the species. Though the natural 

 history of the Hawaiian birds is of much general interest, it will be seen that 

 the subject of the evolution of the various species presents material foi- con- 

 sideration that is of deep and absorbing interest to all. 



The Family Drepanidid.e. 



The family Drepanidida', which includes the majority of the song birds 

 of Hawaii, is perhaps the most remarkable example of the evolution of a group 

 of birds to be found anywhere. The family which is peculiar to the islands, 

 includes about forty species that are found nowhere else in the world. While 

 they are all much alike in their general structure, they differ amazingly in the 

 form of bill and also exhibit striking differences in the color of the plumage. 

 In almost all other families the form of the bill is (luite uniform among the 

 species that belong to it. That organ usually bears a close connection with 

 the feeding habits of the group, and these are usually very nearly the same 

 for all the species in the family. But among the Drepanidida' of Hawaii we 

 find them fitted by their structure to almost every kind of life for which a 

 song bird in the tropics can become adapted. This adaptation of the bill has 



^~ Buteo solitarius. ^^ Asio accij/itriitux siindcicerisis. 



