XII PREFACE. 



"science is not litei-ature," neither has it any concern with what an 

 author should have done or meant to do, but only with what he 

 actually did. 



Without the special arrangements for the preparation of this work 

 made by the late Dr. G. Brown Goode (as mentioned at the beginning 

 of this preface) and continued by his successors, Dr. Charles D. Wal- 

 cott and Mr. Richard Rathbun, the accomplishment of the task would 

 have been quite impracticable. These arrangements, it should be 

 stated, are all that are possible under existing circumstances, though 

 by no means all that could be desired for its early completion. 



Notwithstanding the great extent of the collection of birds in the 

 United States National Museum, which is much the largest and most 

 nearly complete of any in America, and of North American birds 

 unquestionablj' the finest in existence, so many groups are inadequately 

 represented that it has been necessary to borrow specimens from other 

 collections for study in connection with this work. It is a great pleas- 

 ure to the author that he is able to say that such aid has, almost with- 

 out excejjtion, been most willingly and promptly rendered by those 

 having it in their power to do so. The unrivaled collection of Mexican 

 birds,' as well as very numerous specimens from the United States 

 (including Alaska) and the British Provinces, belonging to the United 

 States Biological Survey (Department of Agriculture) has been kindly 

 placed in the author's hands for study by the Dire^ctor of the Survey, 

 Dr. C. Hart Merriam. The entire collection of each family belonging 

 to the American Museum of Natural History, New York City, has 

 been lent for the same purpose, whenever requested,'* by the authori- 

 ties of that institution, through Dr. J. A. Allen, Curator of the Depart- 

 ment of Vertebrate Zoology, these including many types of Mr. George 

 N. Lawrence, so essential to any investigation of the birds of tropical 

 America. The Academy of Natural Sciences of Philadelphia, through 



1 For this magnificent collection of Mexican birds ornithologists are indebted to 

 the intelligent and energetic labors of Mr. E. \V. Nelson, whose careful, thorough, 

 and protracted field work has covered nearly every portion of that most interesting 

 section of the continent. It illustrates, to a degree which no other collection from 

 that country approaches, the remarkable variations, often within small areas, mani- 

 fest in many of the birds, resulting from unusually varied topographic features and 

 climatic conditions. Without a careful study of Mr. Nelson's collection, which 

 includes the types of numerous new species and subspecies described by him, a fairly 

 accurate knowledge of the geographic distribution and variations of Mexican birds 

 would not be possible. The inestimable value of this collection in the preparation 

 of the present work has been greatly enhanced by Mr. Nelson's kind assistance, both 

 verbally and by means of a map, colored by him to show the different faunal areas, 

 thereby explaining most clearly why marked variations often occur in birds of locali- 

 ties not far separated as to distance but in reality very different in physical character. 



^ These include, to date, their entire representation of the families of Fringillidie, 

 Icteridss, and Corvidse. 



