THE BIRDS OF NORTHERN THAILAND 507 



Motacilla flava thunbergi, de Schauensee, Proc. Acad. Nat. Sci. Philadelphia, 

 1929, p. 561 (Chiang Rai). — Deignan, Journ. Siam Soc. Nat. Hist. Suppl., 

 1931, p. 154 (Chiang Mai) ; 1936, p. 121 (Chiang Mai). 



Budytes thunbergi plexus, Riley, U. S. Nat. Mus. Bull. 172, 1938, p. 473 (Ban 

 Nam Ehian). 



This race of the yellow wagtail is a common winter visitor through- 

 out the northern lowlands ; at Chiang Mai it has been recorded from 

 October 27 (1936) to March 14 (1930), but I have collected it at 

 Mae Sariang as early as October 6 (1936) and at Ban Tong Yang 

 as late as May 4 (1936). 



The present species occurs in wet fields and at grassy areas beside 

 ponds and marshes ; at the period of the northward migration, when 

 the countryside is largely desiccated, it gathers at such places in 

 great numbers and appears to be more abundant than it really is. 



Prenuptial molt is to be seen in examples from Nan Province, col- 

 lected April 2 and 13. 



A male had the irides brown; the bill black, with the base of the 

 mandible plumbeous ; the feet and toes dark brown ; the claws brown- 

 ish black. 



The adult male has the forehead, crown, and nape bluish slate; 

 the remaining upperparts olive-green ; the wings blackish brown, the 

 feathers edged with creamy yellow along the outer web; the two 

 outermost pairs of rectrices largely white, the remaining pairs black ; 

 the lores and ear coverts blackish or slaty ; the entire underparts bright 

 yellow (often whitish at the point of the chin) ; the thighs brownish 

 ashy. The adult female differs from the male in having the forehead, 

 crown, and nape duller and suffused with olive-green and in having 

 the underparts less bright yellow. The young in first-winter plumage 

 (seen very commonly in autumn) has the entire upperparts brownish 

 ashy; the wing feathers edged with creamy white; a narrow white 

 supercilium ; the lores and ear coverts brownish ashy ; the underparts 

 white, more or less strongly washed with buff, especially on the breast 

 and lower throat; the under wing coverts and axillaries buffy white 

 or buffy cream. 



The male from Ban Nam Khian recorded by Riley (loc. tit.) as 

 plexa is in such worn and discolored plumage as scarcely to be 

 racially identifiable ; to my eye, it agrees best with macronyx. 



MOTACILLA FLAVA ANGARENSIS (Sushkin) 



Baikal Yellow Wagtail 



[Budytes flava] angarensis Sushkin, Proc. Boston Soc. Nat. Hist., vol. 38, 1925, 



pp. 33-34 ("Village Sharagolskaia, Transbaikalia"). 

 Motacilla borealis, Gyldenstolpe, Journ. Nat. Hist. Soc. Siam, 1915, p. 171 (listed). 

 Motacilla flava borealis [partim], Gyldenstolpe, Ibis, 1920, p. 460 ("Northern 



Siam"). 



583136—45—33 



