ROSY-BILLED DUCK 117 



tivity they do not dive as freely as some of their relatives. Finn (1900, 1915) notes 

 that they do not dive much in confinement and that when they do attempt it they 

 show more of a "spring" in going under. 



Flight. These ducks, being large heavy birds with short wings, are clumsy and 

 slow in getting away, but once in the air the flight is swift and direct and often sus- 

 tained for long distances. In the winter season they gather into considerable flocks 

 wherever they are common. Flocks of ten to fifty were seen in Uruguay (Scott and 

 Sharpe, 1912), and Sclater and Hudson (1889) speak of "very large flocks," while 

 Daguerre (1920) says that in winter thousands may be seen together. Sclater and 

 Hudson also state that Rosy-bills can perform long journeys traveling in extended 

 lines at a considerable elevation. When Mr. J. L. Peters was at Las Yngleses, eastern 

 Buenos Aires, in May, 1920, he was fortunate in seeing a great migration of these 

 ducks. It began early in the afternoon of the 11th and continued until late the next 

 morning, with a scattered flight for another day or two. The flocks were from thirty 

 or forty up to one hundred and were mostly composed of male birds. He spoke 

 of them as roughly V-shaped. 



Association with other Species. E. Gibson (1920) mentions their flocking 

 with Brown Pintails in the autumn, and of their supposed parasitic nesting habits 

 there will be occasion to speak in connection with the breeding activities. 



Voice. The voice of the male is not striking or loud. I have heard it from 

 captive birds in the nesting season and find it described in my notes as a "little 

 whining, mewing call, constantly uttered and certainly resembling that of the Com- 

 mon Pochard, which was calling at the same time." Wetmore (MS.) was fortunate 

 enough to see the male courting in its native surroundings, and describes the note of 

 the drake as "a purring Jcah-h-h, a low call that carried for only a short distance." 

 Hudson (P. L. Sclater and Hudson, 1889) described the male's note as a "deep, 

 hoarse, prolonged, raven-like note," but it seems most likely that he heard the 

 female, which is said to have a loud quacking note like that of the Red-crested 

 Pochard, but somewhat harder (Heinroth, 1911). 



The remarkable trachea of the male is 220 mm. long and the central portion is 

 greatly expanded, forming a roughly spherical pouch 30 mm. long and 25 mm. broad. 

 A similar structure is found in the Velvet Scoter and the Harlequin. The osseous 

 bulb at the bifurcation of the windpipe, faces to the left and forward and is very 

 peculiar, although it is of the same general type as found in some other diving ducks. 

 It has a shape somewhat like that of a lima bean with the outer rim greatly thick- 

 ened and bony and the sides consisting of thin, transparent membrane. It is 20 mm. 

 long and 16 mm. wide in its greatest dimensions. This remarkable organ was first 

 figured by Garrod (1875). 



