16 BULLETIN 186, UNITED STATES NATIONAL MUSEUM 



Son Province as identical with the Salwin drainage, Chiang Mai 

 Province as equal to that of the Mae Ping, Lampang Province as 

 equal to that of the Mae Wang, Phrae Province as equal to that of 

 the Mae Yom, Nan Province as equal to that of Mae Nan, and Chiang 

 Rai Province as equivalent to all northern territory drained by the 

 Mae Khong. 



Northern Thailand may be looked upon as essentially a plateau, 

 somewhat tilted, so that it is higher to north and west than to south 

 and east; while the level of the alluvial plain at Chiang Rai Town is 

 about 1,200 feet, that at Chiang Mai is about 1,000, and that at Nan 

 only 656 feet. From this plateau, however, arises so great a confusion 

 of hills and mountains that only in Chiang Rai Province (itself an 

 embouchure of the Mae Khong) and elsewhere at occasional embou- 

 chures, great or small, along the major streams do we find any sizable 

 areas of level land. For most of their courses, the streams flow be- 

 tween precipitous banks and rapids are of frequent occurrence; the 

 population, dependent upon lands suitable for riziculture, is largely 

 concentrated upon the comparatively limited area composed of allu- 

 vial plain and walled in by hills. 



MOUNTAINS 



The mountains of northern Thailand, whether of limestone or gran- 

 ite, are notable for the steep pitch of their slopes and the usual ab- 

 sence of a belt of foothills between them and the plains at their bases. 

 In ascending or descending them, the zonal distribution of plants and 

 animals is thus strongly marked, and without loss of time several 

 biotas may be visited within a single day. 



Our knowledge of the avifauna of the northern hills has necessarily 

 been gained chiefly by sampling, and inasmuch as scarcely a known 

 peak has failed to produce forms apparently absent from its nearest 

 neighbors it is evident that the mountain birds of our area cannot 

 be considered understood until every peak rising above 3,000 feet 

 has been carefully worked. Those mountains from which virtually 

 our entire information has been derived are the following : 



1. Doi Pha Horn Pok, 7,532 feet, highest peak of the Daen Lao 

 range, situated astride the Thai-Shan frontier about 48 miles west- 

 northwest of Chiang Rai ; it is the only known Thai locality for Bam- 

 biisicola, Dryobates cathpharius, Garrulax merulinus, and other forms 

 common to the northward. 



2. Doi Chiang Dao, 7,160 feet, second highest peak of the Thanon 

 Thong Chai range, situated about 40 miles north by west of Chiang 

 Mai ; it is a solid block of limestone rising from a base elevation of 

 only 1,312 feet. 



3. Doi Suthep, 5,500 feet, a classical collecting ground of the Tha- 

 non Thong Chai range, situated just west of Chiang Mai. 



