388 BULLETIN 133, UNITED STATES NATIONAL MUSEUM 



January young still in ju venal plumage were found near San 

 Vicente, Uruguay, while at Rio Negro other young were seen dur- 

 ing 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 bay- 

 winged 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 be- 

 come 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. 



