23 



species, and in the finer points of classification ornithologists 

 do not always agree; also there is a constant evolution going 

 on in nature. Manv of the races now recognized mav be 

 species in the making. If for any reason the connecting links 

 in the chain of subspecies between the pallid or desert song 

 sparrow and the Aleutian song sparrow had disappeared, these 

 two birds would probably be recognized as well-marked species. 



Two races of the same species — the pallid song sparrow and the Aleutian song sparrow. 



Years ago the heath hen (now extinct except on the island of 

 Martha's Vineyard, Massachusetts) and the prairie chicken were 

 considered by Audubon as one species, and described as the 

 pinnated grouse. Since that time all connecting links betw^een 

 the eastern bird and the western bird have been extirpated, and 

 now we have tw^o distinct species. On the other hand, the 

 western meadowlark, Sturnella negleda of Audubon, is now 

 considered by some ornithologists to be no more than a race 

 of Sturnella magna, of which we may perhaps have to record 

 three principal North American forms :^ Sturnella magna magna ^ 



' other races have been described, but they are mainly birds of the southwest or of Mexico 

 and Central America. 



