21 



be followed faithfully eack species eventually will have a fixed 

 name by which it will be known everywhere. Unfortunately 

 synonyms have multiplied until they have become the despair 

 of the beginner, who prefers, instead, such vernacular names as 

 robin and bluebird, which have become* stable and widely used 

 and recognized. The American Ornithologists' Union has 

 turned its attention, also, to stabilizing the common names of 

 birds, and both common and technical names for each species 

 are published in the Check List of the Union, which is the 

 recognized authority for names of North American species; 

 but even now changes not infrequently occur. Fixity in the 

 names of species might have been reached before now, as it is 

 some years since a new species of bird has been observed in 

 North America, but an increased acquaintance with the classi- 

 jBcation of the birds of the world, also with the early literature 

 of ornithology, and the names in use in other departments of 

 zoology, have necessitated many changes in order to conform 

 with the rules. Also the specimens of birds in public and pri- 

 vate collections have never been sufficient in number or rep- 

 resentative enough geographically to give the systematic 

 ornithologists the material necessary for final and accurate 

 determination. The continual discovery of new subspecies, as 

 material in ornithological collections has increased, has called 

 for new names, and has required continual changes. 



Species and subspecies of the same genus differ in appearance 

 from each other mainly in color and size. In the early history 

 of ornithology the species was the unit, but more recently the 

 comparison of many individuals of a species from different 

 parts of its range has led to a recognition of minor differences 

 in size or color, or both. For example, individuals from the 

 northern part of the breeding range of a species may be larger 

 and lighter or darker in color than those in the southern part, 

 while those at mid-range may show size and color intermediate 

 between the two. The two or more geographic forms of a 

 species exhibiting fixed differences are therefore described as 

 races or subspecies, — as Caucasians, Mongolians, and Negroes 

 are characterized as races of man. Ornithologists in naming 

 these races now use the trinomial, or three-name, system. 

 The generic and specific names together denote the species. 



