24 MOULTS AND PLUMAGES 



MOULTS OF THE ADULT FEMALE 



During the winter and spring, the adult female undergoes a grad- 

 ual and inconspicuous moult, including the body-feathers and tail but 

 not the wings. The feathers are replaced by others which are identical 

 with those moulted. This moult is known as the "prenuptial" moult. 

 (In the case of the Scaups and Ring-necks the plumage becomes browner 

 during the breeding season, even the white mask becoming brown or at 

 least much obscured.) 



Towards the end of this moult the female sheds her inner coat of 

 down, which, in waterfowl, is found most abundantly on the underparts. 

 This down is immediately replaced by a similar coat and, in addition, 

 the female is now provided with a special "nest down." This nest down 

 is longer, softer, and more strongly constructed. As its name implies, it 

 is chiefly this special down that the female plucks from her breast to 

 line her nest. 



In the late summer the female undergoes another moult of the 

 entire plumage, this time, including the wings. This moult is known as 

 the "post-nuptial" moult, and is complete in August or September; thus 

 it is that the female, during the autumn, is found in her full, new, 

 winter plumage. 



JUVENILE PLUMAGE 



Usually within a period of three weeks after hatching, the downy 

 young commences to acquire its first true feathers known as the "juve- 

 nile" plumage. The wing-feathers are the last to appear, the young bird 

 being then about 3 months old and practically fully grown. 



Very shortly after the juvenile plumage has been completed (usually 

 in August or early September), the young bird commences to moult 

 into its "first winter" plumage. This is acquired in typical ducks, by a 

 continuous moult between September and May. 



In the autumn, therefore, the young birds are found in various 

 stages of the moult from juvenile to fully adult dress, and, as the season 

 progresses, they become more and more like the adult birds. The juve- 

 nile wing is not moulted until after the first eclipse moult during the 

 following summer, when the young bird is about one year old. In most 

 cases, the plumage of the young bird becomes fully adult following its 

 first eclipse moult, when about 15 months old. 



During the first autumn, young males resemble adult males moult- 

 ing out of eclipse (except for the wings), and young females are prac- 

 tically identical with adult females. Up to late autumn or early winter, 

 juveniles may be distinguished from adults by methods described in the 

 section headed "Sex and Age Determination." 



The rate of the moult from juvenile to adult plumage varies greatly 

 in the various species, and even in individuals of the same species. The 

 Eiders and Scoters take several years to reach full adult plumage. 



