xxviii HISTORICAL FBEFACE. 



no better than hairsplitting, and the liberties of the " American idea " must never 

 degenerate into license. Our action in this regard must stop short of a point where an 

 unfavorable reaction would be the inevitable result. 



But I have digressed, in saying a warning word, from the point of the conclusion of 

 this Preface, which is simply to describe the new edition of the " Key " with special 

 reference to its difference from the former one. The classification and nomenclature are 

 materially different, in consequence of the progress of our knowledge during the past twelve 

 years. In 1873, a year after the old "Key" appeared, I published a " Check List," con- 

 formed exactly with the nomenclature of the "Key." In 1 882, when I had recast the "Key," 

 I published a second edition of the " Check List " in conformity with the new " Key." 

 The present work, therefore, gives the same names, Avith scarcely any variance, though with 

 a few additional ones; the new " Check List" and the new " Key" being practically one 

 in all that pertains to nomenclature, and representing a particular phase of the subject. 

 The numbering of the species, also, corresponds Avith that in the " Check List." 



Part I. of the present work consists of my "Field Ornithology," originally published as 

 a separate treatise in 1874, and now for the first time incorporated with the " Key." It is 

 reprinted nearly verbatim, but with some little amplification towards its end, and the intro- 

 duction of a few illustrations. 



Part II. consists of the introductory matter of the old " Key," very greatly amplified. 

 In its present shape it is a sort of " Closet Ornithology " as distinguished from a " Field 

 Ornithology ; " being a treatise on the classification and structure of birds, explaining and 

 defining the technical terms used in ornithology, — in short, teaching the principles of 

 the science and illustrating their application. 



Part III., the main body of the work, describes all the species and subspecies of 

 North American birds known to me, defines the genera, and characterizes the fainilies and 

 higher groups. The descriptions are much more elaborate than those of the old " Key," 

 and I trust that such amplification has been made without loss of that sharpness of 

 definition which was the aim of the first edition. I have kept steadily in view my main 

 purpose — the ready identification of specimens. In many cases I have drawn upon my 

 other works — such as the "Birds of the Colorado Valley," the "Birds of the North- 

 west," and several of my Monographs, — for available ready-made descriptions ; but for 

 the most part the matter of this kind is new. Scarcely any of this part of the old 

 " Key " remains as it was. One improvement, I think, will be found in the removal of 

 the unnecessary references to authorities which closed the descriptive paragraphs of the 

 old " Key," and the utilization of the space thus gained by introducing terse biograph- 

 ical items, with special reference to nests and eggs, to song, flight, migrative and other 

 habits ; the technical descriptions of the species thus also epitomizing the life-history of 

 the birds. Geographical distribution is also more fully treated, as its importance de- 

 serves. More attention has been paid to the description of the plumages of females and 

 young birds. The specific names head their respective paragraphs, instead of tailing-oflf 

 the same ; they are also marked for accent, and their etymology is concisely stated, — 

 though for this matter the student should continue to use the new " Check List." 



As regards the artificial " key to the genera " of the old work, it has proven that 

 too much was attempted in undertaking to carry the student at once to our refined mod- 

 ern genera. I have accordingly substituted artificial keys to the orders and families ; 



