X INTRODUCTION. 



as to inc'Uulc all the species known to inhabit Socorro Islantl, ofT the coast of north- 

 western Mexico, which is decidedly Nearctic, or North American, in its zoological 

 aflSnitie.s, while in many cases other extraiimital 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,' Culian, 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 Tultinares, 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. 



Material. — Although the unrivalled collection of American birds and their 

 eggs forming part of the National Museum' has furnished bj- 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 Citj- ; the Academy of Natural Sciences 

 of Philadelphia ; the Boston Society of Natural History- ; the Museum of Compara- 

 tive Zoology, 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 extraiimital species or more extensive scries 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 Uniicr the head of " Mexican" are includoJ not only Mexico itself, but also Guatemala and Honduras. 

 (See page vii, regarding typographical distinction between extraiimital 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 .SC.Onn, exclusive of duplicates and mounted specimens ; the North American " study scries" of 

 Pameren and " Picarire" {i.e., Macrochirce, Pic!, and Cocri/i/cs) alone aggrcf;ating nearly LI, 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 .'58,400 specimens, constitirting 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 sjieeies represented 

 or in their careful identification, it having from the commencement been made a rule to destroy all specimens 

 regarding which there appeareil the least doubt or suspicion. Captain Hendire's celebrated collection, whilo 

 representing fewer species, included far more extensive series of a largo number of species, showing extreme 

 variations of size, contour, and coloration, all perfectly identified, whilo it was wholly unique in the cxquisito 

 preparation of the specimens. 



' Special mention should be made of Mr. Ilcnshaw's valuable collection (embracing more than 7000 speci- 

 mens and unusually complete scries of many species), which through the owner's courtesy has been constantly 

 accessible to the author. 



