Bulletin - United States National Museum - si-pddr - Smithsonian ...

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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, supposed
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 somewhat
more finely vermiculated, the black markings on the sides narrow,
and the brown of the breast somewhat duller. These differences,
however, are so slight as to seem almost intangible, though it seems