XXviii HISTORICAL PREFACE. 
no better than hair-splitting, 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 1882, 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, with 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 with 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 families 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-off 
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 ; 
