SEX AND AGE DETERMINATION 33 



(4) AGE DETERMINATION BY FOOT COLOUR 



In species which have bright-coloured feet (Mallard, Black Duck, 

 Shoveller, and to a lesser extent the Wood Duck, Blue-winged Teal and 

 Gadwall) the foot colour of the adult male is usually brighter and more 

 intense than the foot colour of the juvenile male in autumn. There is 

 considerable variation, however, and this is not reliable as an age cri- 

 terion. 



In females, the foot colour of the adult and the juvenile shows little 

 contrast, and foot colour is not a character of age in the female. (Note: 

 The "foot" includes the tarsus, and is popularly referred to as the 

 "leg." See Glossary.) 



(5) SEX AND AGE DETERMINATION BY THE CLOACAL METHOD 



Both the sex and the age of a specimen can be determined by an 

 examination of the cloaca or anal chamber. 



SEX DETERMINATION 



The sex of the specimen is instantly identified by the presence or 

 absence of the penis character, which is, of course, present only in the 

 male. 



AGE DETERMINATION 

 THE MALE PENIS AS AN AGE CHARACTER 



The age of the male is told by the degree of development of the 

 penis. 



The penis of the male shows two stages of development: (a) In 

 immature birds it is merely a small, unsheathed, fleshy appendage at- 

 tached to the forewall of the cloaca just within the cloacal lip, in ap- 

 pearance like a tiny pigtail, (b) In adult birds the penis is a large 

 white or greyish, corkscrew-like organ, which is held in a conspicuous 

 sheath, an outgrowth of the left cloacal wall. The differences between 

 the penis of the adult and the juvenile may be seen at a glance. See 

 fig. 29. 



In considering the penis as an age character it is necessary to class 

 the birds in two groups: 



Group 1. Species in which the adult penis is always assumed during 

 their first winter or spring, and in which the juvenile penis never per- 

 sists in yearling birds. This group is known to include the Mallard, 

 Black Duck, Gadwall, Baldpate, Green-winged and Blue-winged Teals, 

 Pintail, Shoveller, Wood Duck, Canvas-back, Redhead, Ring-necked 

 Duck, Lesser Scaup and Ruddy Duck; and probably includes the Mot- 

 tled and Florida Ducks, European Widgeon, European and Cinnamon 

 Teals and Greater Scaup. In all of these species the adult penis is 

 never assumed before the end of December. In some young males of 

 all species the juvenile penis persists until April or May, but after the 



