152 BIRDS OF LA PLATA 



large number of birds appear to pair for life, as they 

 are usually seen in pairs at all seasons of the year* 

 In the autumn and winter months I have sometimes 

 observed small flocks composed of males only/ but 

 these were perhaps young birds not yet paired. They 

 feed in shallow water, where by plunging the head 

 down they can reach the mud at the bottom ; and 

 when several are seen thus engaged, all with their 

 heads and necks immersed, they look curiously like 

 headless ducks floating on the water* When dis- 

 turbed or flying the male emits a low sputtering 

 sound, and this is its only language. They are 

 resident, and the least wary of ducks ; never engage, 

 like other species, in real or mock combats ; and 

 their flight is rapid and violent, the wings beating 

 quickly* 



ROSY-BILLED DUCK 



Metopiana peposaca 



Above black, back of head and neck glossed with purple, back 

 finely striated with white ; speculum white ; primaries greyish white ; 

 belly minutely vermiculated with white and grey; bill rosy red, 

 enlarged at the base, feet yellow; length 19, wing 9.4 inches. Female : 

 above brown, bend of wing, speculum, and belly white ; bill and feet 

 dull blue. 



THE Rosy-billed Duck, usually called " Black Duck " 

 in the Plata, inhabits the Argentine country from 

 Paraguay to Patagonia, and also occurs in Uruguay 

 and Chili, but does not extend to Brazil* 



