200 THE BIRDS OF SIKHIM. 



of water, precipitated by the excessive rainfall of this the rainiest 

 section of the Himalayas. For, lying immediately opposite the top of 

 the Bay of Bengal, and not being screened, like Bhutan, by intervening 

 hiUs, Sikhim receives the full force of the monsoon storms from 

 the south, thus acquiring the leading feature of its climate, viz., 

 dampness — the steamy heat of the lower hUls and tarai, and the cold 

 dripping dampness of the upper forests of its outer ranges. The 

 average rainfall of these latter is about 130 inches per annum, and 

 they are cloud-capped for a great part of the year. 



Tortuous rivers seam the face of the country in every direction. 



j^. The chief effluent river of Sikhim is the Tista, 



which flows in a generally southerly direction, and 

 has for its headwaters the Lachhen and Lachhung, which unite at 

 Tsiinthang. The main branch of the Tista is the Great Rungeet, which 

 joins it within the mountains. The depth of the gorge of the Tista 

 and the Rungeet and other large tributaries is almost incredible. About 

 thu'ty miles within the hills, the beds of the Tista and Rungeet are only 

 about GOO feet above the sea level, and their banks thoroughly tropical. 

 These great rivers carry a tropical and subtropical climate along 

 their banks far into the interior of the country, till the semi-tropical 

 vegetation becomes almost overhung by snow peaks. 



Thus the ridges of the innumerable spurs form peninsulas and j^ro- 

 TT • i_ J! 1- X montories of relatively temperate climate, running 

 out into the sub-tropical areas of the deep ravines. 

 In this way the gradations of climate are almost endless ; and some of 

 the inner and more land-locked valleys came to possess a relatively 

 dry climate. In lower and outer Sikhim the even outline of the hills 

 is seldom broken by cliffs or bluffs, and the valleys are usually ravine- 

 like, with the rivers flowing in deep gorges. In Upper Sikhim the 

 scenery becomes much bolder, cliffs are frequent, and the forest tends 

 to be confined to the bottom of the valleys, which latter open out 

 frequently into wide grassy meadows, such as at Lachhung and Yum- 

 thang. Throughout the greater part of Sikhim perennial streams and 

 evergreen forest offer grateful resom-ces to birds. There are few 

 lakes, and those which do exist are mostly of very small size. 



r,y .. The climate of this country may be divided in 



Chmatic zones. , ■ •, j> • x -i j ii • 



respect to its fauna into the lollowing zones : — 



T T «• 7 ( ^''^T''^''^" (l^erton^e^d W 125-2,000 feet 

 I.-Tropical or Tarat. | ^^^ ^ifio.^^t above the sea level. 



iHiUy j 



Il.—Suh-tropical 2,000 to 5,000 feet. 



III.— Temperate 5,000 to 9,000 „ 



J v.— Sub- Alpine 9,000 to 13,000 „ 



V—Alpine 13,000 to 17,000 „ 



