AVES LARID^. 1 95 



Culmen, 4 inches. 

 Bill (tip to gonys), 4.9 inches. 

 Tarsus, 1.4 inches. 



Female smaller, only about 16.5 inches total length, the culmen being 

 2.7 to 2.8 compared with 4 inches for culmen in male. 



Fig. 118. 



Rhyncliops niclaiuira. Bill from above. Frommaterial in the American Museum. Natural size. 



Color. — Adult male (breeding). General color of the upper parts black, 

 of the lower parts white. 



Head: Forehead (to the depth of an inch), lores and sides of face from 

 just below the eye white. Crown and remainder of head black. 



Neck : Black above and abruptly white on sides and beneath. 



Back : Mantle, rump and upper tail coverts black, with a brown tinge. 



Wing : Black with a brown tinge ; the primaries black, the three or four 

 outer ones with the tips and terminal margins white ; the secondaries with 

 a narrow white end to each feather ; no other wi)ig feathers with white 

 markings. 



Tail : Dark blackisJi brow}i on its upper surface, witJi very narrow 

 white edging ; paler brown on its under surfaces. 



Lower parts white, except the tinder wing coverts, which are greyish 

 brown. 



Bill : Reddish orange, yellow at the base, anterior portion black. 

 Tarsi : Dull orange, shaded with black. Feet : Toes and webs dull 

 orange, shaded with black. Iris : Dark hazel brown. 



I have been unable to examine the winter phase of the adult plumage, 

 and have seen no immature, young'or nestlings. All of these phases of 

 plumage, however, are probably similar to those of R. nigra, with which 

 this species has frequently been confused even down to within a few years. 



