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388 BULLETIN 133, UNITED STATES NATIONAL MUSEUM
January young still in juvenal plumage were found near San
Vicente, Uruguay, while at Rio Negro other young were seen during
the middle of February. A fledgling was taken here on February
17 from an old nest of Pseudoseisura lophotes. The large domed
structures constructed by this species are very durable so that they
resist the weather for a considerable time after the tracheophones
are through with them. Though I searched a number at various
times I did not succeed in finding eggs of the cowbirds.
The call notes of this cowbird are harsh and emphatic, chrut or
check repeated incessantly when the birds are anxious about some
nest site. The males utter a sweet warbling song, a pleasant melody
that has earned the species the sobriquet of musico, a name well
warranted. Even during the breeding season little bands of baywinged
cowbirds were found in company often voicing their sweetly
modulated whistled song to the accompaniment of the more prosaic
bubbling of Molothrvs honariensis. During winter bay-winged cow-
birds gathered in little bands of 20 to 50 members that frequented the
vicinity of ranch buildings or little open savannas in the Chaco,
where they fed on the ground or rested in close companies in the tops
of low trees. Their brown wings distinguished them easily from
other blackbirds.
Young in juvenal plumage are similar to adults, but are faintly
and indistinctly streaked with whitish below, and spotted obscurely
with dusky on crown and back.
ARCHIPLANUS ALBIROSTRIS (VieiUot)
Cassictis albirostris Vieillot, Nouv. Diet. Hist. Nat., vol. 5, 1816, p. 364.
(Paraguay.)
The genus Archiplanus Cabanis, with the present species as its
type, has been separated from Cacicus by Miller ^^ on smaller, more
wedge-shaped bill, with culmen and commissure nearly straight,
shorter, more rounded wing tip, with ninth primary shorter than
third, and (usually) better developed aftershaft. Miller has in-
cluded in Archiplanus the species current as Cactus chrysopter-us,
C. chrysonotus^ C. leucorainphus^ and the bird described by Dubois
as Agelaius sclateri. Todd^^ has also recognized Archiplanus as
distinct and has added to it the species previously knoAvn under the
name Airiblycercus solitarius.
With removal of the present species, known in recent years as
Cacicus chrysopterus (Vigors), to Archiplanus its name will become
Archiplanus albirostris Vieillot, a specific name not available
81 Auk, 1924, pp. 463-465.
saproc. Biol. Soe. Washington, vol. 37, July 8, 1924, pp. 114-115.