ORGANIC EVOLUTION 



241 



PIG. 149. Hawaiian birds of 

 the family Drepanidas (after 

 Jordan and Kellogg). /, 

 Oreomystis; 2, Pseudones- 

 tor; 3, Heterorhynchus ; 4, 

 Hemignathus; j, Chloridops. 



dom, even single orders when of 

 dominant types (such as the great 

 order Coleoptera of insects , 1 50 ,000 

 species), will furnish equally 

 striking illustrations. Indeed the 

 best examples of adaptive radia- 

 tion are furnished by small groups 

 that are dominant within a restric- 

 ted range. The family Drepanidae 

 of birds in the Hawaiian islands is 

 such an example. The singing 

 birds of these islands are all 

 members of this single family. 

 All are much alike in internal struc- 

 ture, and in all essential family 

 characters, but they differ much 

 among themselves in form of beak 

 (fig. 149) and in other minor 

 characters, as the accompanying 

 outline figure of a few representative 

 selected forms will clearly indicate. 

 These differences are correlated with 

 much greater differences in feed- 

 ing habits than are usually found 

 among the members of a single 

 family. In our own fauna, for 

 example, this order of birds 

 (Oscines) is represented by a num- 

 ber of families: the families of the 

 thrushes, the finches, the orioles, the 

 warblers, the sparrows, etc., in each 

 of which there is found one form of 

 bill, and a general family resemb- 

 lance. But the single family 

 Drepanidae, in exclusive possession 



