INTRODUCTION 



Naming Birds. — Since birds have evolved from a rep- 

 tilian state and are still in the very slow process of evolution 

 to still higher forms, it follows that the natural and proper 

 order in which our present birds should be arranged is from 

 the lowest and most reptile-like form upward. Following 

 such an arrangement our birds are grouped into orders com- 

 mencing with the Grebes and ending with the Bluebirds. The 

 birds comprising each order agree in certain structural fea- 

 tures, even though they may often be quite unlike externally. 

 A comparison of the members of an order shows that the one 

 group can be divided into perhaps several smaller groups of 

 birds which agree structurallyin other less important respects. 

 These second divisions are known as Families. For instance, 

 the Order Pygopodes, which is composed of certain diving 

 birds, contains Family ColymbidcE or Grebes, Family Gaviidm 

 or Loons, and Family Alcidae, Auks, Murres, and Puffins. 

 These families may often advantageously be still further 

 divided into Genera, and finally we come down to the in- 

 dividual Species. 



When widely distributed, the same species of birds are 

 subject to sometimes great and permanent differences in their 

 plumages. Although widely separated birds sometimes show 

 even greater differences in their plumage than between many 

 other distinct species, the two races cannot be regarded as 

 distinct since birds in the regions between the extremes inter- 

 grade gradually with one another; hence the one bird is called 

 a subspecies of the other. In order to distinguish between 

 the subspecies, the trinom.ial method of naming is used. This 

 may be best illustrated by the following example. 



Our comm.on Song Sparrow is a very widely distributed 

 bird; in fact, it is found throughout the United States and 

 the greater part of Canada and Alaska. This bird is ap- 

 parently very susceptible to climatic changes, for, while in 

 the Eastern States we have but one race, in the West there 

 are a great many subspecies, nineteen at the present time. 

 As a rule, birds of northern chmes are larger than the same 

 kind in the South; also birds in regions of large rainfall are 

 much darker colored than the same kind in hot, dry climates. 



