x INTRODUCTION. 
as to include all the species known to inhabit Socorro Island, off the coast of north- 
western Mexico, which is decidedly Nearctic, or North American, in its zodlogical 
affinities, while in many cases other extralimital species have been included, for the 
sake of comparison and also on account of the greater or less probability of their 
occurrence within the southern boundary of the United States. In most cases this 
ignoring of geographical limits has been confined to the inclusion of only the Mexi- 
can,! Cuban, and Bahaman species of characteristically North American genera, or 
of genera from the same regions belonging to North American Families, the Euro- 
pean analogues of certain North American species, and species of northeastern Asia 
which have been ascribed to Alaska, or which may from the close proximity of 
their habitat be expected to occur there. A notable departure from this general 
rule has, however, been made in the Order Tubdinares, consisting wholly of species 
inhabiting the “high seas,” whose more or less erratic or fortuitous wanderings 
render them specially liable to a place in the list of “accidental visitors” to any 
sea-girt country, for which reason it has been considered desirable, as an aid to 
future research, to include all known species belonging to genera of which repre- 
sentatives have been taken in North American waters. 
Mareriau.—Although the unrivalled collection of American birds and their 
eggs forming part of the National Museum? has furnished by far the greater por- 
tion of the material upon which this work is based, several other public museums, 
as well as rich private collections, have been carefully studied. Thus, the American 
Museum of Natural History, in New York City ; the Academy of Natural Sciences 
of Philadelphia; the Boston Society of Natural History ; the Museum of Compara- 
tive Zodlogy, in Cambridge, Mass.; and the splendid private collections of Messrs. 
George N. Lawrence, of New York City, William Brewster, of Cambridge, Mass., 
and H. W. Henshaw,’ of Washington, D.C., have furnished indispensable material 
in the way of extralimital species or more extensive series of certain North Amer- 
ican species, for comparison, than had yet been secured by the National Museum. 
It is not, however, the large number of specimens alone that has furnished the sub- 
stantial basis of the following synoptical tables; for, however much the proper dis- 
1 Under the head of “ Mexican” are included not only Mexico itself, but also Guatemala and Honduras. 
(See page vii, regarding typographical distinction between extralimital and North American species.) 
? The total number of specimens of American birds in the National Museum collection at the end of June, 
1886, was about 36,000, exclusive of duplicates and mounted specimens; the North American “ study series” of 
Passeres and “ Picariz”’ (t.e., Macrochires, Pict, and Coccyges) alone aggregating nearly 13,000, counting only 
those obtained from North America proper, as defined in the A. 0. U. Check List. At the same time, the collec- 
tion of North American birds’ eggs numbered 38,400 specimens, constituting by far the most extensive and valu- 
able one in existence. Even before the addition of the magnificent private collection so generously donated by 
Captain Charles E. Bendire, U.S.A., no other was comparable to it, either in the number of species represented 
or in their careful identification, it having from the commencement been made a rule to destroy all specimens 
regarding which there appeared the least doubt or suspicion. Captain Bendire’s celebrated collection, while 
representing fewer species, included far more extensive series of a large number of species, showing extreme 
variations of size, contour, and coloration, all perfectly identified, while it was wholly unique in the exquisite 
preparation of the specimens. 
5 Special mention should be made of Mr. Henshaw’s valuable collection (embracing more than 7000 speci- 
mens and unusually complete series of many species), which through the owner’s courtesy has been constantly 
accessible to the author. 
