4 



48 JOURNAL, BOMBAY NATURAL HIST. SOCIETY, Vol. XXIII. 



well-marked geographical races or sub-species over the extent of its 

 distribution. 



A great number of birds which are found both in Southern India 

 and Lower Burma are very similar, and often hardly separable. Fellor- 

 neum ruficeps ruficeps, Swainson, and Alcip)pe fliceocepliala plimoce- 

 pliala, Jerdon, both from Madras, and at one extremity of the " horse- 

 shoe " are very like P. r. suhocliraceum, Swinhoe, and A. p. p)^^ct'yTei, 

 Blyth, from Lower Burma and Tenasserim, at the other extremity, 

 while separating them we have well marked races. Many other inter- 

 esting examples might easily be given, Mr. Stuart Baker has also 

 noticed the same fact whilst working at the Game Birds and Pigeons. 



These same unknown reasons might also account for the niimerous 

 cases of similarity or " mimicry' 'which exist between birds of totally 

 different genera and orders, such a,B 'bet\\een Mixornis ruhricapillus , 

 Tickell, and Stachyrhidopsis 'nificeps (Blyth), which from their color- 

 ation are only separable after careful examination. Dicrurus ater, 

 CrypsirJiina varians and S'ltrniculus luguhris (the King-crow, Black 

 racket-tailed Pie, and the Drongo-cuckoo) can all be very easily 

 mistaken for each other. 



The distribution of the " Plains Dwellers" is natiu'ally restricted 

 by mountain ranges and desert tracts, whilst that of Hill birds 

 appears to be limited by certain great river valleys. This is most 

 marked in what may be called the " Assam Back-water." Here we 

 find in the same Province many birds from one side of the river are 

 quite distinct from those of the other, some sub-species, from the 

 Dafla Hills to the North of the Brahmaputra being quite distinct 

 frora those from the Garo, Khasia and Cachar hills, situated to the 

 South of the river. 



I do not wish to imply that each area has its own special breed of 

 birds, but if there is any variation in a species, these differences will 

 probably occur within certain well-marked tracts. I may possibly be 

 wrong in my different areas as I only came to the following conclu- 

 sions, from stTidying specimens and not from any local knowledge, 

 except in the case of Burma. 



In the Himalayas, we find the following rivers forming very 

 natural boundaries, the IndiTS, Sutlej and Brahmaputra. In Burma 

 in a less degree we still have small rivers marking well defined 

 areas. In this Province the most noticeable barrier is the " dry- 

 zone" of Central Biwma, which effectually separates Northern 

 Burma from Lower Burma, and the Chin Hills on the West from 

 the Shan Hills on the East. 



India. 



Commencing at the N.-W. we have the following well-marked 

 areas : — 



1. Tra7is-2ndus. — Probably from the right or West bank of the 



