CHAPTER FOUR 



CLASSIFICATION OF BIRDS 



ROBINS, bluebirds, and thrushes belong to the same 

 family of birds. This family does not include any of 

 our other birds. The others belong to other families, of 

 which there are many, some including many species, 

 some only a few. The birds of one species are all nearly 

 alike, except for differences due to age, season, sex, or 

 some unusual peculiarity. The bluebirds of the eastern 

 part of North America are all of the same species. In 

 the Rocky Mountains are bluebirds of other species. 

 The birds of a blue color in the eastern part of North 

 America are not all of one species. The blue jay and the 

 indigo bunting, for instance, are conspicuous for their 

 blue color, but they are not bluebirds and do not even 

 belong to the same family as the bluebirds. To classify 

 birds by color alone would be like classifying people by 

 the clothes they wear. It might not always be wholly 

 useless, but it would not group the birds in a natural 

 way. 



Birds classified according to natural relationships. 

 Naturalists put in the same family those species of birds 

 which are closely related to each other. The members 

 of the thrush family, including the bluebird and robin, 

 are believed to be actually related, in the same sense that 

 you and other descendants of your great-grandparents 

 are related. Of course the relationship of these birds is 

 not so close as that. It may be better compared to your 

 relationship with every person of your own race. If 

 you had a complete genealogy going back many thou- 

 sands of years, you would find that all the persons of a race 



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