372 



RUDDY AND MASKED DUCKS 



Masked Duck 



Nomonyx dominicus 

 (no-mon-iks, do-min-i-kus) 



Colour Plate No. 31. 

 SCIENTIFIC NAME 



Nomonyx, from Greek, nomos, meaning law, order, and onux, meaning nail, 

 i.e., nail of bill ordinary; dominicus, Latinized form, meaning of St. Domingo, an 

 island republic in the West Indies. 



COLLOQUIAL NAMES 



None in North America. 



DESCRIPTION 



ADULT MALE. WINTER AND SUMMER PLUMAGE: Head, from bill to ear 

 region, including crown, black; hindhead and neck, dark rusty cinnamon (from 

 its black face it gains the name "masked"); some individuals have a white chin; 

 bill, smaller than that of Ruddy Duck, pale blue, ridge and nail, black, lower 

 mandible whitish or reddish white, tipped with black; eye, dark brown; eyelids, 



pale blue. Body. Back and scapulars, dark rusty 

 cinnamon, with conspicuous dusky or black feather- 

 centres, giving a dark striped effect; rump, dark 

 brown, marked with black, some feathers white- 

 edged; chest, rusty cinnamon or brown, marked 

 with black and reddish buff; sides and upper 

 breast, rusty cinnamon or brown, marked with 

 black; lower breast and belly, whitish, often stained 

 with rusty; feet, outer side of tarsus and two 

 outer toes, dark brown or black, inner side of 

 tarsus, inner toe and webs, pale brown, spotted 

 with black (outermost toe not longest, as in Ruddy 

 Duck). Tail, blackish; upper coverts, black, barred 

 FIG. 57 Bill of Masked and marked with white; under coverts, same as 

 Duck breast; tail-coverts, short, barely covering bases of 



(Compare FIG. 55) tail-feathers. Tail, fan-shaped and of quill-like 



feathers as in Ruddy Duck. Wings. Lesser coverts, brownish black; middle coverts, 

 brownish black, tipped with white; inner greater coverts, brownish black, outer 

 ones white; primaries and tertials, dark brown; secondaries, with white speculum, 

 tipped with black; lining, deep brownish grey, with some light edges and tips; 

 axillars, white. 



ECLIPSE PLUMAGE: There is no eclipse plumage. It is possible that the Masked 

 Duck loses its brilliant colouring during the post-nuptial moult in autumn, as 

 does the Ruddy Duck. 



ADULT FEMALE. Head. Crown, dark brown; cheeks, chin and throat, creamy 

 to white, with two dark stripes on cheek, one through eye and one from base of 

 bill to ear; neck, dark brown, feathers edged with buffy; bill, brown, with black 

 tip; eye, same as that of male. Body. Foreback, same as neck; back, scapulars and 

 rump, brownish black, feathers tipped and notched with buff; breast, whitish; belly, 

 greyish buff, with brownish-grey bars to feathers; chest and sides, dusky, barred 



