152 Mr.O. B. Ticelmrst on [Ibis, 



feathers have dark bases which show up when abraded, 

 giving a streaked appearance ; in picata the head is quite 

 black like the mantle. It has been suggested that this is a 

 dimorphism — a black-headed and white-headed form of one 

 species — as is found in leucopyga ; but in the latter the head 

 is black or white or particoloured, quite different from the 

 isabelline grey of capistrata : also it has been said that every 

 intero-radation between black-headed and white-headed forms 

 occurs ; a relatively small ])ercentage certainly do occur in 

 which the colours of the head are mixed, and with these I 

 will deal later on. 



{b) In the adults of both the mantle is glossy black : in the 

 first winter picata this is usually as glossy as in the adult, 

 but in the first winter capistrata it is always duller, a sooty 

 or brownish black. 



(c) On an average the wing of capistrata is longer than 

 that of picata ; the great number of measurements which I 

 have carried out (over 60 of each) shows well how wrong an 

 impression may be given by the statement that wing lengths 

 vary between two extremes; thus the total variation in 

 p>icata is from 89-99 mm, and in capistrata 90-99 mm., and 

 judging by this one would at once say that the size is the 

 same in both ; but when analysed these measurements show 

 that 73 per cent, of picata are between 91 and 94, and 80 per 

 cent, of capistrata measure 94 or more, or put in another 

 way graphically in the form of a curve, that of picata has 

 fallen to zero just as that for capistrata has reached its 

 apex. 



II . Characters in the juvenile plumage. 



There are plenty of specimens of juvenile picata in collec- 

 tions, but none for certain of capistrata. It is known that 

 the juvenile of the former is dark brown above, but at 

 Gilgit, where both species breed, two forms of juveniles 

 occur, a darker and a lighter brown (quite apart from sex) ; 

 this is ver}' suggestive ; moreover from Turkestan, whence 

 I have only seen capistrata, from the same locality there 

 is a juvenile of the lighter brown type. 



