160 LIST OF BIRDS IN MANIPUR, 



[Fairly commoa in the Dibrugarh district. About the be-' 

 ginning of March the birds, on dissection, show signs of breed- 

 ing. Gape, eyelids and orbital skin are yellow. Insects and 

 hard seeded berries are what I have found they fed ou. — 

 J. R. C] 



413. — Garrulax moniliger, Hodgs. 



I only found this species in Manipnr in the same localities 

 as and in company with 0. pectoralis. 



To me these two species, differing as a fact only in size, have 

 always presented a most puzzling problem. I say differing 

 only in size, because, though each varies a good deal and you 

 may pick out specimens of the one differing very markedly 

 in plumage from specimens of the other, as a fact both vary 

 in precisely the same fashion, so tliat you can match any 

 shade or variation of plumage in the one with a precisely 

 similar variation in the other, if only you have sufficiently 

 large series of both. 



Well then, differing only in size, they are almost always found 

 in the same localities, whether it be Tenasserim, Northern Pegu, 

 Arakan, the Tipperah hills, Cachar, Manipur, the Khasi hills, 

 Assam, the Dafla hills, the Bhotan Dooars, Sikhim or Nepal ; 

 wherever the one occurs, there the other also is sure to turn 

 up. One may be rare and the other common, but except 

 possibly in Southern Pegu, where the one is, there is the other 

 likewise. Nay they very commonly, as in the Manipur 

 Western hills and many parts of Tenasserim, &c., &c. (see also 

 IX, 181), go in mixed flocks ; yet one never gets any of 

 intermediate sizes. 



Is there any other such pair of species ? There are many- 

 other pairs differing similarly only in size, but then they 

 belong to different localities, and where their distribution 

 areas interlace or overlap we do get intermediate forms. , 



How is the existence of these two forms to be explained 

 on our modern principles of evolution ? They breed in the 

 same localities at the same time. They are not like some 

 of the small waders said to have a smaller and larger form, 

 some bred in temperate and some in high arctic regions. 



They must have had a common ancestor ; their food is the 

 same (I have compared the contents of the stomachs of three 

 of each shot in the Barak valley at the same time and the 

 insects were the same in each ), and so far as we can judge 

 they have, scecula sceculorum, been exposed to the same cir- 

 cumscribing conditions, and how then can Ave explain their 

 persistent and sharply defined difference of size. To me this 



