292 



XOVITATES ZOOLOGICAE XXV. 1918. 



of this river, there is a great cUflference in depth of colour between the darkest 

 and palest individuals from one and the same locaUty. Thus from Arrakan, 

 Chin Hills, Shan States, Lower Burma, and Tennasserim both dark and Light 

 birds may be, and in manj- instances have been, obtained in the same locahtj' 

 on the same date, whilst other specimens, intermediate in colour, have also 

 been obtained which could be assigned to either with equal accuracy. Even 

 from the extreme north-west of India and Simla, whence most specimens arc 

 very level in tint, very dark and very pale bu-ds may be met with, and there 

 are examples of both extremes in the big Simla series in the British Museum. 



At the same time colour cannot be entirely ehminated from classification 

 of these birds, for it is very e\ident that — 



(1) On the whole birda west of the Brahmapootra are decidedly darker 

 than those on the east, though there are individuals found in the latter 

 practically as dark as any on the west. 



(2) A steady decrease in depth of colour is found as one works south, 

 though this tendency to paleness is more accentuated in southern Burmese 

 than in southein Indian birds. 



As regards the formation and length of tail, these features are of little assis- 

 tance in discriminating between the different geographical races of D. leucopMcvs, 

 although there is no doubt that birds from the extreme south-east have typically 

 shorter, less forked tails than those from the north and west. 



We are therefore throv\n mainly on characters other than those of colour 

 to enable the geograpliical races to be worked out, and it woukl appear that 

 size, combined with some consideration of comparative length in wing and tail 

 and average depth of coloui', will allow of this being done with a sufficient degree 

 of accuracy. 



To show this at a glance 1 give the following measurements of birds from 

 various areas, giving maximum and minimum as well as average figures. 



EA8T OF THE BRAHMAPOOTRA. 



From the above measurements it is self-evident that as we work from 

 north to south vve get a steady diminution in size. In India 1 cannot find that 



