How Brirps ARE NAMED. 
The study of the distribution of birds and the mapping of their 
natural life-areas are also intimately connected with this recognition 
by name of their geographical variations, but into this phase of the” 
subject we will not enter. : 
Since it is evident that a bird may vary much or little, according to 
the governing conditions and its tendency to respond to them, no 
fixed rule can be laid down which shall decide just what degrees of 
difference are deserving aname. It follows, therefore,that in some cases 
ornithologists do not agree upon a bird’s claim to subspecific rank. 
In North America, however, questions of this kind are referred to a 
committee of seven experts of the American Ornithologists’ Union, 
and their decision establishes anomeclature, which is accepted as the 
standard by other American ornithologists and which has been adopted 
in this volume. : 
Foreign birds of wholly accidental occurrence, most of which have been 
found in North America but once or twice, are included in the systematic 
list of North America birds, but are not described or figured in the body 
of the book, where their presence would tend to convey an erroneous im- 
pression of their North American status. Furthermore, records of the 
presence of birds so rare as these can be properly based on only the 
capture of specimens. 
In the preparation of the following pages both author and artist have 
had full access to the collections of the American Museum of Natural 
History, and they are also glad to acknowledge their indebtednesss to 
William Brewster of Cambridge, Massachusetts, to Robert Ridgway, 
Curator of Birds in the United States National Museum, and to C. 
Hart Merriam, Chief of the Biologic Survey, for the loan of specimens 
tor description and illustration. 
