THE BIRDS OF NORTHERN THAILAND 373 



Provinces, where suitable jungle grows at feeble elevations, it occurs 

 at the very bases of the hills. 



This is a wholly arboreal form that, in flocks, large or small, and 

 often accompanied by tits and nuthatches, travels rapidly along the 

 edges of clearings and forest tracks, busily investigating the leaves 

 and cracks in the bark or even hanging head-downward from the 

 ends of twigs, all the while uttering notes not unlike those of a 

 titmouse. 



A specimen with the gonads enlarged was taken on April 18, but 

 another with them greatly enlarged was collected as early as March 

 23. Birds in full ju venal plumage were found on April 25 and May 

 10. Postnuptial molt is shown in examples of August 27 and 29 and 

 postjuvenal molt in one of September 9. 



An adult female had the irides brown; the maxilla horn, with the 

 edges of the commissure fleshy ; the mandible fleshy ; the interior of 

 the mouth bright yellow ; the feet, toes, and claws fleshy. 



The adult of either sex has the entire upperparts, including the 

 crest, golden-olive, the remiges and rectrices narrowly margined with 

 yellow along the inner web; the lores, narrow eye ring, ear coverts, 

 and imderparts white, more or less strongly suffused with ashy; the 

 under coverts of wings and tail yellow. The juvenile is similar but 

 has the nape and mantle strongly suffused with tawny. 



I can distinguish only four continental races of this species: 

 tyrannula, zantholeuca, interposita, and canescens, of which only the 

 last may be known definitely by color characters. Among the other 

 three we find, from north to south, a gradual increase in length of 

 wing and heaviness of bill, with tyrannula and interposita represent- 

 ing the extreme forms and zantholeuca the intermediate. E. z. sor- 

 dida (paratypes examined), described from worn specimens (March, 

 May ) , seems to be quite inseparable from zantholeuca. 



ALCIPPE CASTANECEPS EXUL Delacour 



Indo-Chinese Chestnut-capped Babbler 



Alcippe castaneiceps exul Delacour, L'Oiseau et la Revue Franchise d'Orni- 



thologie, new ser., vol. 2, No. 3, 1932, pp. 427-428 (Phu Kong Ntoul, Bolovens 



plateau, Bas-Laos). 

 Pseudominla castaneiceps castaneiceps, de Schauensee, Proc. Acad. Nat. Sci. 



Philadelphia, 1934, p. 194 (Doi Suthep). — Deignan, Journ. Siam Soc. Nat. 



Hist. Suppl., 1936, p. 107 (Doi Suthep). 

 Pseudominla castaneceps castaneceps, Riley, U. S. Nat. Mus. Bull. 172, 1938, 



p. 356 (Doi Ang Ka, Doi Langka, Doi Hua Mot). 

 Pseudominla castaneiceps exsul, Greenway, Bull. Mus. Comp. Zool., 1940, p. 173 



(Doi AngKa). 



This diminutive babbler probably occurs on all the northern peaks 

 whose slopes are heavily forested above an elevation of 5,000 feet. 



