THE BIRDS OF NORTHERN THAILAND 



15 



Thong Chai and Khun Tan ranges is the Mae Ping; the one between 

 the Khun Tan and Western Phi Pan Nam hills, the Mae Wang ; the 

 one between the two ranges of the Phi Pan Nam, the Mae Yom; the 

 last one to the east, the Mae Nan. These four must be understood to 

 belong to a single drainage system, quite unrelated to the systems of 

 the Salwin and the Mae Khong. (Map 2.) 



Map 2. — Drainage systems of northern Thailand: 



1. Mae Khong. 4. Mae Wang. 



2. Salwin. 5. Mae Yom. 



3. Mae Ping. 6. Mae Nan. 



The watersheds of the six main rivers of Northern Thailand are 

 almost exactly equivalent to the six principal political divisions so 

 far as they lie within our limits ; so close is this correspondence that, 

 throughout this study, I have found it convenient to treat Mae Hong 



