156 JOURNAL, BOMBAY NATURAL HIST. SOCIETY, Vol. XXIII. 



Wing 170 mm., middle tail-feather 51 mm., lateral tail-feathers 75 mm. 

 Mr. Tom Iredale, m.b.o.u., has pointed out to me the following interest- 

 ing differences between this new sub-species and the Large White-rumped 

 Swift from China. 



"■ In the typical M, p. pacificus, the wing is very long, with narrow 

 elongate feathers. The second primary noticeably the longest, the first 

 about 8 mm. shorter, whilst the third is about 12 mm. shorter ; that is, the 

 first is longer than the third ; the fourth about 18 mm. shorter than the 

 third, and the rest correspondingly shorter." 



" In the sub-species M. p. cooki, the first primary is longest ; the wing is 

 shorter, and the feathers broader than in the typical form ; the first is 

 2 mm. longer than the second, which is 10 mm. longer than the third; the 

 third is about 15 mm. longer than the fourth, but the rest do not decrease 

 so quickly as in the previous one." 



"The tails also show corresponding differences. In the typical M. 



pacificus, the tail is long and deeply forked, the tail feathers narrower ; in 



M. p. cooki, the fork is less deep, while the tail feathers are broader. 



M. p. pacificus. — Outer tail feather is 10 mm. longer than second, which 



is 16 mm. longer than third. Fork of tail 35 mm. deep. 



M. p. cooki. — Outer tail feather is 2 mm. longer than second which is" 

 6 mm. longer than third. Fork of tail 24 mm. deep. 



It is a well known fact that migratory birds, which are generally accus- 

 tomed to cover long distances, generally have long pointed wings, and as 

 soon as they give up the migratory habit, their wings become shorter and 

 broader. 



This is very well exemplified in the " Flight of Birds " Series in the 

 Natural History Museum, where the wings of the European House Martin 

 {S. u. urbica, L. ) and the Algerian House Martin ( H. u. meridional^', 

 Hartert) are displayed. The former being a highly migratory species, 

 summering in Northern Europe and migrating for the winter to Africa, 

 whilst the latter is a resident species, spending the whole year in North 

 Africa. These differences closely correspond with those of the two Swifts. 

 M. p. pacificus, breeds in Siberia and North China and migrates to 

 Australia, and has consequently a long pointed wing, whilst M. p. cooki 

 is in all probability strictly resident, or only leaves its breeding haunts for 

 a very short time, and has therefore developed a shorter and broader wing, 

 I first noticed the Burmese Swift in the Goteik Gorge in February, when 

 they were flying about near the railway bridge in thousands. In June I 

 paid a visit to the famous caves, where I found them breeding. Mr. J. P. 

 Cook informs me that he found them inhabiting some caves about 30 miles 

 north of the Goteik Gorge, in Yatsauk State ; where they were literally in 

 thousands, this was in October, they can therefore only leave their 

 breeding haunts at the most for two or three months, and in all probability 

 do not leave at all. This point can easily be settled if members of the 

 Society at Maymyo or in the Northern Shan States would report whether 

 the Swifts are seen in the Gorge in the months of November, December and 

 January . 



Distribution. — Probably throughout the Shan Plateau, and breeding in 

 the numerous lime-stone caves which are found throughout that region. 

 There are the following specimens in the British Museum, besides those 

 collected by Mr. Cook and myself : — 1 specimen collected by J. Davison 

 5. 7. 74. at Amherst and 1 specimen collected by Thompson 7.1.01. at 

 Maukmai. 



Nesting. — In June I found the Burmese Swift breeding in thousands in 

 the Goteik caves, which form a natural bridge through which the river flows, 

 and over which is constructed the railway viaduct (which is said to be . the 



