INTEODUCTION. 



The task of compiling a list of the known species of Birds becomes 

 very difficult when the Passeriformes are approached, and I have 

 found an extraordinary increase in the number of the MuscimpidcB 

 and Pi/cnonotidcf, since I wrote the fourth and sixth volumes of the 

 ' Catalogue of Birds ' in 1879 and ISSl. 



Apart from the work involved in picking up the threads since the 

 ' Catalogue ' was finished, the question of Classification presents grave 

 difficulties in the case of the Passeriformes. A good deal of sterling 

 work has been done during recent years, but we are still far from 

 a satisfactory system as regards the Passerine birds. Although the 

 late iMr. Seebohm afterwards admitted that he ought to have included 

 Pratincohi, Cossypha, etc. in the fifth volume of the ' Catalogue,' that 

 does not account for all the difficulties of the question ; but I have, of 

 course, not enumerated such genera as these among the Flycatchers. 

 There remain, however, many doubtful forms in the Mvscicapidtt, and I 

 have followed Mr. Eugene Gates in some of the modifications which he 

 has introduced in his excellent volumes of 'Aves' in the ' Fauna of 

 Britisli India.' Genera like Cryptolopha, Parisoma, Polioptila, etc. may 

 just as well be Si/luii'hr as Sericomis, Aranthiza, and Ihjpolais; and it 

 seems extremely difficult to draw a line between the Flycatchers and the 

 Warblers. In face of the uncertainty which surrounds the classifica- 

 tion of the Old-World Passeres, I have adhered, in the present volume, 

 mainly to the order of Vol. IV. of the ' Catalogue.' 



Proofs of this volume have been sent to many of my colleagues 

 abroad, and the assistance they have rendered me requires my sincere 

 recognition. 1 have tried everywhere to acknowledge the original 



