BIRDS OF ARGENTINA, PARAGUAY, URUGUAY, AND CHILE 229 



plumage on the throat, with more feathers of the same color in 

 process of groAvth aromid it. The male until it dons adult plumage 

 has a white spot behind the eye like that found in females. Imma- 

 ture birds of both sexes are duller above than adults. 



Present understanding of the geographic forms of ChlorostiJbon 

 aureo-ventHs is highly unsatisfactory. Simon has described a 

 southern form,^ including a range from southeastern Brazil to 

 Buenos Aires, but has complicated matters by calling egregius a 

 form of C. 'prasina. The subspecific variations of aureo-ventris 

 must for the present remain clouded in doubt. 



ChloTostUhon aureo-ventris was recorded at the following points: 

 Riacho Pilaga, Formosa, August 11, 14, and 18, 1920; Lavalle, 

 Buenos Aires, October 29 to November 15; San Vicente, Uruguay, 

 January 26 to February 2, 1921 ; Lazcano, Uruguay, February 3 to 

 9 ; Rio Negro, Uruguay, February 14 to 19 ; Tapia, Tucuman, April 

 7, 8, and 13. Individuals were seen during July, 1920, near Las 

 Palmas, Chaco. 



During winter these hummers were encountered occasionally at 

 the border of forests and thickets, where they received the warmth 

 of the sun and were protected from cold winds. Small shrubs that 

 were in flower were frequented, and I saw them gleaning insects 

 from the limbs of trees. In the pampas during summer hummers 

 came in small numbers to flowers about the estancias or occasionally 

 dropped down into the inclosed patios of small country hotels. On 

 January 26, near San Vicente. Uruguay, a female flashed by me in 

 a forest of palms, and on glancing up I caught sight of her nest 

 placed on a swinging bit of fern root, 12 feet from the groimd, be- 

 low the crown of leaves that formed the top of the tree. To my 

 great disappointment the nest was empty. It was of the usual hum- 

 mer type, a soft, cup-shaped structure made of plant downs and 

 fine bark, covered with fragments of brown bark fastened in place 

 with spider webbing. 



Near Tapia, Tucuman, this hummer, with others, frequented the 

 red flowers of an abundant epiphyte {Psittacanthus cuneifoUus). 



A female, taken August 14, had the tip of the bill black, and the 

 basal half orange-cinnamon, the two colors blending at the point of 

 junction; iris Rood's brown; tarsus and toes fuscous; nails black. 



OREOTROCHILUS LEUCOPLEURUS Gould 



Oreotrochiliis leucoplenrus Gould, Proc. Zool. Soc. London, 1847. p. 10. 

 (Chilian Cordillera.) 



Near Potrerillos, Mendoza, two females were secured on March 

 16 and 19, 1921. This species is more sluggish in its movements than 



» ChlorostWbon aureiventris tucumaniis Simon. Hist. Xat. Troch., 1921, p. 65. 

 (Tucuman.) 



54207—26 16 



