A SUBSPECIES. 133 



that all these birds are not the same species, because there 

 is no fixed difference between them. 



But it becomes convenient to have some way of showing 

 that there are differences. So we cut the species up into 

 pieces, as it were, just as we did the apple. We take the' 

 whole range of the species and divide the country up into as 

 many portions as there are peculiar varieties of the species, 

 and give to all the birds of the species that live in each section 

 a name that tells the scientist just what part of the country 

 the bird comes from. Most birds do not have any sub- 

 species; that is, they are alike wherever we find them. Of 

 the rest, most do not have more than one subspecies besides 

 the original form, one of them being found in the East and 

 the other in the West. But some, and they are usually among 

 our best-known birds, have three or four or a half-dozen sub- 

 species. The ruffed grouse has four, the downy woodpecker 

 five, the hairy woodpecker six, the horned owl five, the 

 screech owl nine, the horned lark eleven, and our common 

 song sparrow twelve recognized forms. Sometimes a sub- 

 species will be found only on a small island far off from land, 

 sometimes on a desert, or sometimes confined within other 

 narrow limits, but most of them are spread over a large extent 

 of country. Because these subspecies are found in different 

 parts of the country, they are frequently called " geographical 

 races." 



It is often supposed that the birds with two Latin names 

 are the only ones of any importance, and that those with 

 three names are a mere afterthought of science or nature. 

 This is an error. When a species is split up into different 

 forms, all the forms composing it are subspecies, and one is no 

 more important than another unless it is more abundant. 

 When you cut an apple, all the parts are fractions ; when you 



