190 BULLETIN 186, UNITED STATES NATIONAL MUSEUM 



less trees on the low hills west of Ban Na Noi (Nan Province), April 

 1, 1937. The extreme dates for its stay on Doi Suthep are September 

 26 (1936) and April 2 (1931). 



Probably no bird in the world surpasses the present species in speed 

 of flight, which doubtless on occasion exceeds 100 miles an hour. To 

 appreciate its velocity one must have braced oneself against the wind 

 on some treeless, knife-edged ridge, where the mountain falls away on 

 either hand into an abyss, and heard the swish of wings as an individ- 

 ual hurtled by, just skimming the rocks and, apparently intentionally, 

 almost grazing the observer, then curving in a wide arc far beyond 

 and returning to repeat the spectacular performance. Throughout 

 the daylight hours, however strong the gale, it is the very incarnation 

 of tireless flight. 



The spinetail has a conspicuous patch on the lores pure white ; the 

 head, nape, wings, and tail black, highly glossed with greenish blue; 

 the back brown ; the underparts brown, paler on chin and throat, and 

 slightly glossed with green on the upper breast ; the under tail coverts 

 pure white with black shafts, the white continued as a narrow line 

 along the lower flanks above the thighs. 



APUS PACIFICUS COOKI (Harington) 



Burmese White-rumped Swift 



Cypselus pacificus cooki Hakington, Bull. Brit. Orn. Club, vol. 31, 1913, p. 57 

 (caves of the Gokteik Gorge, Hsipaw State, Northern Shan States). 



Micropus pacificus cooki, de Schauensee, Proc. Acad. Nat. Sci. Philadelphia, 

 1934, p. 266 (Doi Chiang Dao). 



The white-rumped swift occurs with us only rarely, but it has been 

 observed in some numbers on several occasions. De Schauensee found 

 it common on Doi Chiang Dao, where he took a female at 4,500 feet, 

 January 19, 1933. It was numerous at a place near Ban Hua Fai, on 

 the track from Muang Fang to Muang Hang, December 27, 1936, and 

 I collected a male there. Finally, a flock of these birds appeared on 

 Doi Suthep at 2,800 feet, January 2, 1937, and I succeeded in shooting 

 two females. 



De Schauensee notes that his specimen had the irides dark brown ; 

 the bill, feet, toes, and claws black. 



This rather large species has the entire upperparts, except for a 

 narrow white rump band, black, more or less glossed with greenish ; 

 the throat white with narrow black shaft streaks, not clearly defined 

 from the remaining underparts, which are black, with each feather 

 broadly tipped white so as to give a barred appearance. 



Of the swifts now known from our provinces, this species can be 

 confused only with the smaller house swift, which is unbarred beneath. 

 There is a possibility, however, that the northern white-rumped swift, 

 A. p. pacificus, will also occur with us in winter ; from the present form 



