850 PATAGONIAN EXPEDITIONS: ZOOLOGY. 



gestures and actions. Swelling and ruffling his feathers like a turkey- 

 cock, and frequently suddenly taking wing and flying directly away from 

 the female, and performing a wide circuit round her in the air, he sings all 

 the time. The song begins with remarkable hollow, internal notes, ending 

 with others loud and clear. The female is homely in appearance in her 

 dull mouse-coloured suit, and has no song but a low chattering, not often 

 uttered, and always appears very indifferent to the advances of her beauti- 

 ful glossy partner. In the evening, when they settle on the trees to roost, 

 they sing until it is quite dark. From their great numbers, their singing 

 at such times often sounds like the rushing of a strong wind among the 

 trees. When disturbed on their roost at night the males repeat their song 

 as they take wing ; they also settle on the trees on rainy days to sing, con- 

 tinuing their concert for hours. 



"It is well known that, like the European Cuckoo, it deposits its eggs in 

 the nests of other birds. But the Cuckoo lays but one egg in a nest, and 

 its peculiar habit possesses one thing in common with the instincts of 

 other animals ; it is regular and definite, ensures the safety of the young, 

 and, for all that has yet been established to the contrary, is unchangeable 

 as are the laws of matter and force. The instinct of the Blackbird is, on 

 the contrary, unsettled and indefinite and truly a 'monstrosity.' . . . 



"In autumn, when the Blackbirds congregate in flocks of tens of thou- 

 sands, so that the ground where they feed seems carpeted with black, and 

 the trees where they alight to have a black foliage, I often wonder that the 

 little birds in whose nests they lay do not become extinct, or all but 

 extinct, by their means." (P. Z. S. 1870, pp. 548-550.) 



Genus AGELAIUS Vieillot. 



Type. 



Agelaius Vieillot, Analyse, 1816, p. 33 . Oriolits phceniceus Linnaeus. 



Agelaius thilius chrysopterus Vieillot. 



Agelaius chrysopterus Vieillot, Nouv. Diet. Hist. Nat. 181 9, 34, p. 539 



(Paraguay). 

 Agelaius thilius chrysocarpus Auct. (nee A. chrysocarpus Vig.). 



Description. — Adult male, 284265 Berazategui, Buenos Aires, Argen- 

 tina, June 29, 1920, Alexander Wetmore. Total length, 6.82 inches ; wing, 

 3.40; culmen, .88; tail, 2.70; tarsus, 1.02. Black with a slight gloss; 

 lesser upper and under coverts bright yellow, bill and feet black. In 



