Chapman — Variation in Ostinops Decumanus. 27 



yellow, less frequently yellowish white and rarely white, distributed ir- 

 regularly through the plumage of the body and wing-coverts. 



Type.— No. 138547, Am. Mus. Nat. Hist., d" ad., Yungas (alt. 3600 

 ft.), Prov. Cochabamba, June 3, 1915; Miller and Boyle. 



Consideration of Material Examined. 



Bolivia. — Yungas, alt. 3600 ft., Prov. Cochabamba, 5 o* d\ 5 9 9 

 Locotal, alt. 5800 ft., Prov. Cochabamba, 2 9 9; Todos Santos, alt 

 1300 ft., Prov. Cochabamba, 2 cT cT ; Mission San Antonio, Rio Chimore 

 Prov. Cochabamba, 1 c? ; Tres. Arroyas, Rio Espiritu Santo, 1 d 71 ; Beni 

 River, 1 cf ; Buenavista, Prov. Sara, 2 c 71 o 71 ; Santa Cruz de la Sierra, 1 cf 

 Puerto Suarez, Brazilian boundary, 3 9 9- 



The singular character which, chiefly, distinguishes this proposed race, 

 is evidently most highly developed in the territory at the base of the 

 Andes in Bolivia (Yungas, Locotal, Todos Santos, Buenavista, Santa 

 Cruz). Every one of twenty-one specimens (13 males, 8 females) from 

 this region is more or less conspicuously marked with feathers in whole 

 or part yellow, yellowish white, or rarely white. The specimen selected 

 as type, for example, has yellow or yellow-tipped feathers in the nape, 

 scapulars, interscapulars, greater coverts of the left wing, rump, throat, 

 breast and abdomen. In all there are some sixty feathers of this char- 

 acter. 



In a varying degree all the remaining twenty-one specimens in this 

 series exhibit similar characters', which are apparently more highly devel- 

 oped in the male than in the female. Of thirteen males, twelve have 

 yellow or partly yellow feathers in the scapulars or inner tertials on both 

 sides. There is here, therefore, a degree of symmetry in this marking 

 which does not, however, obtain in connection with the yellow feathers 

 of the body plumage. 



Three females from Puerto Suarez, some 350 miles east of Santa Cruz 

 de la Sierra, on the Brazilian boundary, exhibit the browner tone of colora- 

 tion which appears to characterize the Matto Grosso birds, but a single 

 yellow-tipped feather on the breast of one is the only evidence shown of 

 the type of marking which forms the subject of this paper. 



Peru. — (Rio Cosireni, 3000 ft., lower Urubamba region, 1 c? ; Chauillay, 

 Urubamba Canon, 1 o 71 .) The Rio Cosireni specimen has yellow or 

 yellow-tipped feathers in the nape, back, scapulars, rump, throat, breast, 

 flanks, and tibiae. In the Chauillay bird they appear only in the lower 

 breast and abdomen. These two birds, unfortunately the only ones 

 available from Peru, indicate the disappearance of the "pied" character 

 as one advances northward. Toward the east, from what appears to be 

 its center of highest development, Yungas, Bolivia, it persists more 

 strongly, as shown by a large series from Matto Grosso. 



Southwestern Brazil. — Chapada, Matto Grosso, 16 o 71 cf, 13 9 9; Uru- 

 cum, near Corumba, Matto Grosso, 2 d" o 71 ; 2 9 9 .) This series of thirty- 

 three specimens exhibits as a whole a certain brownish tone which dis- 

 tinguishes it from all our remaining specimens of the species. Possibly 



