So extremely social are these Ducks that even when breeding they keep together in large flocks. The nest is made of stems and leaves, on the water among the reeds and aquatic plants; and sometimes large numbers of nests are found close together, as in a gullery. The eggs are pure white, and each bird lays, I believe, ten or twelve, but I am not sure about the exact number; and I have so frequently found from twenty to thirty eggs in a nest that I am pretty sure that it is a common thing for two or three females to occupy one nest. 341. DENDROCYGNA VIDUATA (Linn.). (WHITE-FACED TREE-DUCK.) +Dendrocygna viduata+, _Burm. La-Plata Reise_, ii. p. 515 (Tucuman); _id. P. Z. S._ 1872, p. 367; _Scl. et Salv. P. Z. S._ 1869, p. 160 (Buenos Ayres), et 1876, p. 376; _Durnford, Ibis_, 1878, p. 64 (Buenos Ayres). _Description._--Face and spot on the throat white; nape, neck in front, middle of abdomen, tail, rump, and wings black; hind neck chestnut; middle of back and scapulars brown, the feathers margined with ochraceous; wing-coverts olivaceous black; flanks banded with black and white; bill and feet black: whole length 17·0 inches, wing 9·0, tail 2·5. _Female_ similar. _Hab._ South America. This Tree-Duck resembles that last described in size, form, and maroon-red plumage, but is of a darker tint, and may also be easily distinguished, even at a long distance, by its white face contrasted with the velvety black of the head and neck. Compared with _Dendrocygna fulva_ it is a rare species, being usually found in pairs in the Plata district, although sometimes as many as half a dozen are seen together. When taking wing it also whistles, but differently from the allied species, having three long clear whistling notes, not unlike the three-syllabled cry of the Sandpiper, only the notes are more prolonged. Of its breeding-habits I know nothing. 342. SARCIDIORNIS CARUNCULATA (Licht.). (CRESTED DUCK.) +Sarcidiornis regia+, _Burm. La-Plata Reise_, ii. p. 513 (Tucuman); _id. P. Z. S._ 1872, p. 365. +Sarcidiornis carunculata+, _Scl. et Salv. P. Z. S._ 1876, p. 377; _Sclater, P. Z. S._ 1876, p. 695, pl. lxviii. _Description._--Head and neck white, spotted with black, hind neck almost black; base of neck and body beneath white; flanks black; back and wings black; secondaries glossed with bronze, the scapulars with purple; lower back grey; tail brown; bill, with caruncle on the culmen, and feet black: whole length 30·0 inches, wing 15·0, tail 6·0. _Female_ similar, but rather smaller. _Hab._ Brazil, Paraguay, and northern confines of Argentina. Dr. Burmeister met with this Duck in the province of Tucuman, and it probably occurs also in other places on the northern frontiers of the Republic. 343. CAIRINA MOSCHATA (Linn.). (MUSCOVY DUCK.)