SOME RECENTLY DESCRIBED SIAMESE BIRDS. 55 



The remaining birds, smaller and rather paler, measure : — 

 Wings, 129 to 139; average 132 mm. 

 Tails, 127 to 155; average 140 mm. 



The bills [on the whole are a little smaller than the 



others. 



The range of the specimens is from Victoria Point through 



Siam to South Annam and they were collected between September 



and May, while Gyldenstolpe secured examples, which seem similar, 



in North Siam during May, June and July (t. c. s., p. 21). 



These birds are apparently B. 1. mouhoti with which they 

 agree in size, though Walden stated that the Cambodian type of 

 this race was darker than the typical Javanese form. I find that, 

 on the whole, the contrary is the case and so did Gyldenstolpe :. 

 however, within narrow limits it appears that much importance 

 cannot be attached to colour, as the tone of the plumage varies with 

 wear and age. (There are among the Siamese series several ex- 

 amples which have the under-wing coverts spotted with white and 

 the vents and under-tail coverts greyish-white, and they are alto- 

 gether paler than the others : on the other hand some adults in 

 much worn plumage are quite as dark as the darkest of Javanese 

 birds). The distinction between the Javan and continental forms 

 seems to lie in the slightly longer tail of the latter, as a series of 

 thirty-four birds from Java measures : — 



Wings, 124 to 139; average 130 mm. 

 Tails, 123 to 145 ; average 132 mm. 



I see no difference in the bills which measure in both from 

 26 to 28. 5 mm.* 



The fact that, according to Bartels, B. I. leucophaea is in best 

 plumage at the end and beginning of the year shows that it does 

 not leave Java at that season and that, apart from smaller size, 

 it is not the same bird as B. I. mouhoti which, judging by the dates 

 on which it has been collected and the occurrence of immature indi- 



* This series shows a higher range than Baker's, in which the 

 tails, measure from 118 to 131, average 123 mm. only (t.c.s., p. 292). 



VOL. IV, NO. 2, 1920. 



