153 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 94 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. 



