388 BULLETIN IS 6, UNITED STATES NATIONAL MUSEUM 



Washington, valuable material from the museums of Philadelphia, 

 New York, and Cambridge. 



It is evident that, in Thailand (except in those regions occupied by 

 the well-marked race connectens), we are concerned with two only 

 slightly differentiated forms with finely streaked throat and breast, 

 one of which has the crown and mantle darker than the other and 

 cannot be distinguished from topotypes of lutescens (which, inci- 

 dentally, do not agree at all with the original diagnosis of the sub- 

 species ! ) . I have seen specimens of this darker bird from Khemmarat, 

 Channuman, Hin Lap, Khorat, Pak Chong, Kaeng Khor, and Lat Bua 

 Khao, in eastern Thailand, from Chiang Saen, Chiang Rai, and Wiang 

 Pa Pao in northern Thailand, and from Muang Len, Sop Lao, and 

 Kengtung Town in the State of Kengtung; those from the last two 

 areas are atypical, yet, in my opinion, nearer lutescens than sulphured. 

 All these localities have in common the fact that they lie in territory 

 drained by the Mae Khong and its tributaries and show that the range 

 of lutescens is bounded, not by the river itself, as suggested by Dela- 

 cour (L'Oiseau et la Revue Francaise d'Ornithologie, 1936, p. 11), 

 but by the limits of its watershed. 



The paler bird, which \ call sulphured, occurs in Thailand across the 

 North from the basin of the Mae Nan to that of the Salwin, in the 

 more western districts south as far as the Gorges of the Mae Ping. In 

 the West, below the Gorges, we find another population, distinguished 

 from sulphured by their more chestnut-rufous crown and from both 

 sulphured and lutescens by their rather heavier streaking of throat and 

 breast ; they are intermediate between sulphured and connectens and, in 

 default of sufficient material, I hesitate to use a definite name for them. 



Judging from analogies, we should expect, in northern Thailand, 

 so plastic a species to be represented by distinct forms to east and west 

 of the Khun Tan chain, but I have been unable to find any important 

 difference between "minor" and sulphured and am forced to believe 

 that racial distribution, in this case, is governed wholly by drainage 

 systems. Such correlation is supported by the fact that this babbler 

 finds its most congenial habitat along streams, large or small — to 

 such an extent that, in the most constricted river-gorges, where dry- 

 land vegetation is reduced to a narrow fringe of bamboo between water's 

 edge and lofty precipice and few birds can exist at all, it is usually the 

 most abundant nonaquatic species. 



TIMALIA PILEATA INTERMEDIA Kinnear 



Burmese Red-capped Babbler 



Timalia pileata intermedia Kinnear, Bull. Brit. Orn. Club, vol. 45, 1924, p. 9 

 (Toungoo, Pegu). 



