2 INTRODUCTION. 



It is true that a few island forms may not come very exactly 

 under this definition, but in these cases the differences are such 

 as are obviously parallel to those obtaining in non-isolated areas 

 on the mainland. Where evolution and isolation have evolved 

 forms which are definitely divided from all others by some 

 characteristic which is not one merely of degree, I have treated 

 them as distinct species. 



In India we are constantly meeting with the most intricate 

 cases of subspecific variation, and a study of birds which admits 

 the recognition of these geographical races and the wisdom of 

 naming them affords infinitely greater interest both to the field 

 and to the scientific worker than does the easier method of 

 lumping them all together. For instance, to take two of out- 

 most common birds, the Indian House-Crow and the lled-veuted 

 Bulbul. Two species of the former and many of the latter have 

 been recognized and given specific names, although the differ- 

 ences between them are in no way specific and are not any 

 greater than the differences which exist in many other forms 

 which have been left undivided. 



The second point to which reference must be made is the 

 unfortunate necessity which has arisen for very numerous 

 corrections in Gates' nomenclature. Such corrections cannot but 

 be a source of some difficulty to the older race of field naturalists, 

 and students who have learnt these names will now have to learn 

 those which replace them. The younger generation will, how- 

 ever, have the satisfaction of knowing that they are learning 

 names which, with few exceptions, will be permanent ; for, with 

 strict adherence to the laws of priority, a time will soon come 

 when we shall really have arrived at the bed-rock of nomen- 

 clatorial research. It should be mentioned here that I have had 

 the unstinted help of Mr. Tom Iredale in this particular branch 

 of the work, and his unrivalled knowledge of bibliography and 

 nomenclature has been of inestimable help to me. 



Another difference between this and the preceding edition will 

 also be noted. With the approval of the editor, Sir Arthur E. 

 Sliiplev, the synonymy has been reduced to references to the 

 original description and to the Blanford and Gates' edition of 

 this work, in the former case the type-locality being given in 

 brackets after the reference. The saving of space thus obtained 

 and the use of briefer descriptions has given additional room for 



