Vlll PREFACE TO FOURTH EDITION. 



or if he would speak of the whole group as a unit he may use 

 '^ Melospiza melodia, The Song Sparrow," just as before. 



The names in heavy-faced type, therefore, represent the kinds 

 of birds recognized in the Check-List regardless of whether they 

 are species or subspecies, that distinction being indicated by the 

 form of the name, binomial or trinomial as the case may be. As 

 a matter of fact while intergradation is supposed to be our cri- 

 terion for the separation of a species from a subspecies, in many 

 cases we do not have specimens showing actual intergradation 

 so that we only infer that it exists. Also there is sometimes 

 difference of opinion as to whether certain forms show intergrada- 

 tion or not, as in the case of the White-crowned Sparrows where 

 opinion is about equally divided as to whether we have three 

 distinct species leucophrys, gambeli, and mdtalli or three sub- 

 species of leucophrys. In other words we encounter all possible 

 degrees of difference and degrees of intergradation in the various 

 groups of birds, and to try to further emphasize a fundamental 

 difference between a species and a subspecies that often does 

 not exist seems misleading. 



Vernacular Names. It was agreed at the outset of the work 

 that the chairman in preparing the text of the new edition should 

 adhere as closely as possible to the English names used in the 

 first edition on the grounds that they have proved more stable 

 than the technical names and in the fifty years or more that they 

 have been in use have built up about them a vast bibhography. 

 At the same time however it was recognized that a quahfying 

 adjective should be added to some names to bring them into 

 proper contrast to others; as for instance "Robin" and " Western 

 Robin," the former of which should obviously be "Eastern 

 Robin." Although both in their respective habitats will be 

 referred to in every day parlance as "Robin" the eastern form 

 has no exclusive right to this name. Sometimes "Northern" 

 or "Southern" have been used in correcting this omission or 

 "American" in contrast to a foreign form that may be included 

 in our List, and where no other term was available "Common" 

 has been employed as in the case of the Tern, Canada Goose and 

 Black Duck, but this word is to be construed as indicating the 

 best known form, not necessarily the most abundant. In some 

 cases an adjustment of vernacular names is by no means easy, as 



