138 On the Nestling-Plumage of the Booted Eagle. 



his adult livery ; whilst the female does not assume the white 

 breast &c. until after one or, perhaps, several moults. It is 

 generally supposed that most eagles in a wild state assume 

 their adult plumage after the third change; but, from the 

 comparative rarity of specimens in the brown plumage, it is 

 possible that the female Nisaetus pennatus may assume the 

 adult livery at the first moult. 



With regard to the male, as I have said, there is little altera- 

 tion from the nestling-plumage beyond a gradual change to a 

 paler cream-colour on the abdomen and flanks, and a gradual 

 narrowing of the striations. These last, however, are by no 

 means a safe guide to the age of a specimen ; for some indi- 

 viduals of the same sex are less streaked than others. The 

 very lightest-coloured male in my series, and lighter also than 

 any breeding female, is pronounced to be a remarkably clean 

 young bird which has never moulted, by Col. Delme*-Radcliffe, 

 who is probably the highest living authority upon raptorial 

 birds. 



I am not writing the history of the Booted Eagle, and it is 

 therefore unnecessary to say more upon the subject ; but the 

 fact of the plumage of the two sexes being different in the 

 nestling stage, and subsequently becoming the same, is, so 

 far as I am aware, unparalleled in any other raptorial bird ; 

 and I have consequently deemed it worthy of being placed on 

 record. 



Note. — I am well aware that nestlings of Archibuteo sancti- 

 johannis are subject to considerable variation ; but it has 

 never been shown that these variations are either sexual or 

 constant. 



