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SOME OBSERVATIONS ON THE BIRDS AND MAMMALS 



OF IMAW BUM. 



By 



F. KiNGDON Ward. 



One of the highest peaks in the Htawgaw Hills, far Upper Burma, on the very 

 threshold of a terra incognita so far as the naturalist is concerned, is Imaw 

 Bum, 13,307 feet. 



These mountains along the China frontier, owing to the incessant rainfall . 

 are snow clad for at least seven months in the year, while the deep valleys are 

 filled with semitropical vegetation; so that we find here one of the most richly 

 assorted floras and densest forest regions in Asia, where animal life in all its 

 forms — including many inimical to man — thrives abundantly. In 1914 I spent 

 four months on the main Salween divide to the east of the Imaw Bum range, 

 from whence I climbed Imaw Bum, and in 1919 I spent a further six months on 

 the western flank of the Imaw Bum range itself, whence I several times reached 

 the Summit of the main peak. 



It is to be noted, then, that Imaw Bum, though one of the highest peaks in 

 the district, is not on the main Salween- — Irrawaddy watershed, but on another 

 axis ruiming parallel to it, and separated from it by the Nagawchang river, which 

 rises from the junction of the two ranges much further north. After flowing 

 south for seventy miles, this river sweeps westwards round the southern end of 

 the Imaw Bum range, and immediately turns due north, again flowing parallel 

 to the main ranges for some forty miles before joining the Irrawady; thus form- 

 ing a complete U. It might then appear that the Imaw Bum range is a feature 

 of original structure, determining the strange course of the Ngawchang river ; 

 but there is reason to beUeve, from differences in the flora of the valleys on either 

 flank of the range, that these valleys, have, in fact, been long isolated, and only 

 comparatively recently become joined up ; that the Imaw Bum range is not 

 then a feature of original structure, but a part of the Salween-Irrawaddy divide ; 

 and that the Ngawchang river is a compound made up of two or more originally 

 distinct streams, that on the west flank of the range having cut its way back till 

 it has reached and beheaded that on the east flank. 



The commanding height of Imaw Bum is doubtless to be ascribed partly to the 

 fact that it is a solid mass of granite, a rock which bulks largely in the district. 



These few topographical details are necessary to any proper appreciation of 

 the distribution of fauna and flora in this region, and thence westwards to the 

 Himalaya and eastwards to China. 



Bird hfe of all kinds abounds on Imaw Bum, from the deep valleys 2,000 feet 

 above sea level to the last of the silver firs and Rhododendron forest at 12,000 

 feet, but more particularly between 6,000 and 10,000 feet ; at least it was so 

 in 1919. 



But in 1914 I remarked in my diary over and over again that birds were pecu- 

 liarly scarce. It did occur to me that since there are many more Lisus in the 

 upper portion of the Ngawchang valley—that is to the east of the range — than 

 i n the lower part, west of the range, this might account for the discrepancy 

 noticed ; for the Lisus are the great destroyers of bird hfe. 



But this explanation was abandoned as too fantastic. Moreover in 1919 I 

 marched right round Imaw Bum, spending a week on the east flank, during 

 which time I saw many birds. 



A possible clue is given by Belt in the "NaturaUst in Nicaragua", where he 

 states.that in the year 1872 there was an epidemic amongst several classes of 

 insects in Chontales. 



