THE BIRDS OF NORTHERN THAILAND 503 



Son, Chiang Mai, and Chiang Rai ; at Chiang Mai Town it has been 

 found between September 19 (1930) and March 29 (1929). The only 

 mountain record is based upon a male collected by de Schauensee's 

 men at 6,400 feet on Doi Pha Horn Pok, February 16, 1938. 



Among the earliest of the winter birds to arrive, these wagtails 

 appear with us in a spectacular manner : where, one day, none is to be 

 seen, the next morning finds them everywhere in town and country, 

 dancing at the margins of pools and streams, strutting across the 

 lawns, parading on the rooftrees, and sweeping in loose bands along 

 the metaled highways. Their numbers fall off somewhat during the 

 cold weather, but locally they become even more numerous just before 

 the northward flight, when suitably moist places are difficult to find ; 

 at this season they may be observed with other species of wagtails. 

 All agree in being long, slim birds which walk or run with bobbing 

 head and constantly moving tail ; all have a characteristic, undulating 

 flight. At Chiang Mai the pied forms are fancifully known as nok 

 um bat, the black pectoral crescent being compared to the begging- 

 bowl (bat) carried (um) before the breast by Buddhist monks. 



No Thai specimen at hand is in molt. Certain individuals, at the 

 postnuptial molt, assume a plumage differing from full nuptial dress 

 only in having the black feathers of the pectoral band very narrowly 

 fringed with white; such birds are of not infrequent occurrence in 

 Thailand. 



A male had the irides brown ; the bill black ; the feet and toes dull 

 black; the soles gray; the claws horny black. A female differed in 

 having the basal half of the mandible gray; the feet and toes dark 

 brown. 



The exceptional examples noted above have the sinciput, lores, ocular 

 region, ear coverts, sides of the neck, the chin, and throat pure white ; 

 the remaining upperparts black ; the upper wing coverts pure white to 

 form a conspicuous shoulder patch ; the remiges black, all with a large 

 patch of white toward the base of the inner web, the primaries nar- 

 rowly, the outer secondaries broadly, edged with white along the outer 

 web; the two outermost pairs of rectrices white except for a narrow 

 black edging toward the base of the inner web, the remaining pairs 

 black; a broad crescentic band of black across the upper breast (the 

 feathers in winter with narrow white fringes) ; the remaining under- 

 parts pure white. Birds in normal winter dress are similar but have 

 the black of the upperparts restricted to the crown, nape, and upper 

 tail coverts; the mantle gray (sharply defined from the black of the 

 nape and upper tail coverts), irregularly sullied with blackish. 



This race is evidently tending toward the complete elimination of 

 a winter plumage distinct in coloration from that of summer. As I 

 have already observed, some individuals acquire the full nuptial dress 



