124 EVOLUTION AND ANIMAL LIFE 



that of the song birds of Hawaii which constitute the family of 

 Drepanidse. In this family are about forty species of birds, 

 all much alike as to general structure, but diverging amazingly 

 from each other in the form of the bill, with, also, striking 

 differences in the color of the plumage. In almost all other 

 families of birds the form of the bill is very uniform within 

 the group. It is correlated with the feeding habits of the bird, 

 and these in most groups of wide range become nearly uniform 

 within the limits of the family. With a great range of com- 

 petition, each type of bird is forced to adapt itself to the special 

 line of life for which it is best fitted. But Avith many diverging 

 possibilities and no competition, except among themselves, the 

 conditions are changed, and we find Drepanidse in Hawaii 

 fitted to almost every kind of life for which a song bird in the 

 tropics may possibly become adapted. (Plate II.) 



In spite of the large differences to be noted there can be 

 little doubt, as Dr. Hans Gadow, Mr. Henry W. Henshav>^ and 

 others have shown, of the common origin of the Drepanidse. 

 A strong peculiar goatlike odor exhaled in life by all of them 

 affords one piece of evidence pointing in this direction. There 

 is, moreover, not much doubt that the whole group is descended 

 from some stock belonging to the family of honey creepers, 

 Ccerebidae, of the forests of Central America. Each of the 

 Hawaiian Islands has its species of Drepanine birds, some olive 

 green in color, some yellow, some black, some scarlet, and some 

 variegated with black, white, and golden. The females in 

 most cases, like the young, are olive green. On each island, 

 most of the species are confined to a small district, to a single 

 kind of thicket or a single species of tree, each species being 

 especially fitted to these localized surroundings. With the 

 destruction of the forests some of these species are already rare 

 or extinct. With high specialization of the bill they lose their 

 power of adaptation. In each of the several recognized genera 

 there are numerous species, mostly thus specialized and local- 

 ized, relatively few species being widely distributed throughout 

 the islands. 



Most primitive of all, least specialized and most like the 

 honey-creeper ancestry, is the olive green Oreoviystis bairdi of 

 the most ancient island, Kauai. This bird has a small straight 

 bill, not unlike that of the slender-billed sparrows. It is said 

 to be the most energetic and ubicpiitous of the group, feeding 



