72 BULLETIN 133, UNITED STATES NATIONAL MUSEUM 



October 28 and a male on November 10 showed no indication of 

 breeding. 



At Tucmnan, Argentina, on April 3 and 5, 1921, tree ducks, sup- 

 posed from their notes to be the present species, passed overhead 

 during the evening toward some feeding ground south of town. 



The typical subspecies may be distinguished fi^om Dendrocygna 

 hicolor helva Wetmore and Peters from North America, by its 

 slightly duller coloration and heavier, broader bill. 



DENDROCYGNA VIDUATA (Linnaeus) 



Anas viduata Linnaeus., Syst. Nat., eel. 12, vol. 1, 1766, p. 205. (Lake 

 Cartagena. ) 



The white-faced tree duck was seen only in the Paraguayan Chaco 

 west of Puerto Pinasco. From September 6 to 8, 1920, the species 

 was fairly common near the ranch at Kilometer 80, and a male was 

 taken here on September 6. The birds rested in flocks on open shores 

 or mud bars at the borders of lagoons, frequently 100 or even more 

 together. They were most active toward night, and at dusk, or 

 even after dark, passed overhead to distant feeding grounds, their 

 approach heralded by their strange, sibilant, whistled calls swee ree 

 ree, swee ree ree. After September 8 these flocks disappeared, but 

 on September 24 and 25 the species was again encountered farther 

 vs est at Laguna Wall, approximately 200 kilometers west of Puerto 

 Pinasco. Flocks seen here ranged in size fro^n 40 to 100. In even- 

 ing the birds circled or passed high overhead, frequently flying in 

 wavy lines like pintails, calling constantly. During early morning 

 and in evening they were observed feeding in shallow ponds, where 

 they waded along, working eagerly in the mud and water like huge 

 teal. As the birds advanced the head was swung from side to side to 

 cover the feeding ground thoroughly, while the silt collected was 

 sifted rapidly through the bill. At this season they were not breed- 

 ing. In Guarani the species is known as suiriri, a good imitation 

 of the call, while the Anguete Indian distinguishes it as kwah te gwi 

 jah. 



The male secured on September C had the soft parts colored as 

 follows : Band across tip of bill, nostrils, and extreme base of culmen 

 puritan gray; rest of bill black; iris Rood's brown; tarsus and toes 

 clear green-blue gray; nails black. 



After careful comparison of a fair series of white-faced tree 

 ducks from both African and South American localities, I am unable 

 to find sufficient grounds to warrant separating birds from the two 

 continents as subspecies. African birds have the upper back some- 

 what more finely vermiculated, the black markings on the sides nar- 

 row, and the brown of the breast somewhat duller. These differences, 

 however, are so slight as to seem almost intangible, though it seems 



