SEX AND AGE DETERMINATION 



37 



(7) SEX DETERMINATION BY WINDPIPE OR TRACHEA 



(Not applicable to Geese or Swans) The lower end of 



the windpipe of all 

 male Ducks is en- 

 larged to form a 

 voice-box (fig. 32). 

 This enlargement is 

 lacking in the wind- 

 pipe of the females. 

 In the case of the 

 Shoveller drake the 

 voice-box is small and 

 undeveloped. As a 

 rule there is also a 

 swelling in rhe upper 



Fie. 32.-T/,, trachea, (a) Windpipe of male; Cnd <>**** < nale w1 ^' 



(b) Windpipe of female P 1 ? 6 * leSS noticeable 



in the case of juvenile 



males; the exceptions to this rule are the Ruddy Duck and the Scoters. 

 (8) SEX DETERMINATION BY VERMICULATIONS 



(Not applicable to Geese or Swans) 



Vermiculations, or fine wavy barring on the feathers of certain 

 areas of the plumage are, with three exceptions, found only on the 

 males of the Ducks. The exceptions are the female Canvas-back and the 

 females of Greater and Lesser Scaups, which show definite vermiculations 

 on the back and scapulars. (Some female Redheads also show vague 

 flecking, approaching vermiculations, on the scapulars.) 



When the adult and juvenile males are in the autumn moult, any 

 vermiculated feathers appearing on such parts of the body as is usual in 

 the full plumage indicate that the bird is a male. 



Among the River and Pond Ducks those that show vermiculations 

 are Mallard, Baldpate, European, Widgeon, Pintail, Gadwall, Green- 

 winged and European Teals, Shoveller, Wood Duck. The Blue-winged 

 and Cinnamon Teals show slight vermiculations in the belly region. 

 (Those without vermiculations are the Black, Florida, Mottled and "New 

 Mexican Ducks.) 



Among the Diving Ducks and Mergansers, those that show ver- 

 miculations are Canvas-back, Redhead, Ring-necked Duck, Greater and 

 Lesser Scaups, American, Red-breasted and Hooded Mergansers. (Those 

 without vermiculations are the Golden-eyes, Buffle-head, Old-squaw, 

 Harlequin, the Scoters, and the Eiders.) 



(9) SEX DETERMINATION BY BILL MARKINGS 



(Applicable only to the River and Pond Ducks) 



Females of most River and Pond Ducks show dusky markings and 

 dark spots on the upper mandible, which markings are lacking in the 

 males. This method of sex determination is applicable to the females 

 of all River and Pond Ducks except the Pintail, Baldpate, European 

 Widgeon, and Wood Duck. (Some female Pintails have well-defined 

 spots on the bill in lake summer and early autumn; these must not be 

 confused with the marking on the bill of the male.) 



