132 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



gions than in the Amazon basin and the central Andes ; but it may also 

 reflect a real difference in the abundance of mixed flocks in these 

 regions. Some observations of my own may be of interest in this 

 connection. 



Both palm tanagers and blue tanagers were observed very fre- 

 quently near Iquitos, in Amazonian Peru, in December of 1958. Ac- 

 cording to Hellmayr (1936), both of these species in this region are 

 subspecifically distinct from the representatives of the same species 

 in Panama ; but most of their habits seemed to be identical with those 

 of the Panamanian forms. The only very distinctive feature of the be- 

 havior of the Iquitos palm tanagers and blue tanagers was their very 

 slight degree of interspecific gregariousness. Individuals of both spe- 

 cies frequently occurred in small flocks of their own species alone near 

 Iquitos ; but they very seldom occurred in mixed flocks and never in 

 highly integrated mixed flocks during my observations in this area. 

 It was particularly surprising that the palm tanagers and blue tanagers 

 near Iquitos did not associate with one another very frequently be- 

 cause they often fed on the same or similar foods in the same trees. 



(The rarity of associations between palm tanagers and blue tanagers 

 near Iquitos may have been partly due to the fact that there were no 

 species of Tangara comparable to the plain-colored tanager in this 

 area. Thus the palm tanagers and blue tanagers near Iquitos did not 

 tend, or did not have the chance, to associate with one another indi- 

 rectly in the same way as the same species in central Panama. But 

 they also joined and followed one another directly much less fre- 

 quently than palm tanagers and blue tanagers in Panama. ) 



As noted above, silver-billed tanagers were also very common near 

 Iquitos. Aside from the one family that occurred in association with 

 the family of black-throated tanagers, the silver-billed tanagers of this 

 area seldom or never occurred in mixed flocks. They were very sim- 

 ilar to crimson-backed tanagers in appearance and actions ; but they 

 did not seem to be nearly as attractive to individuals of other species 

 as crimson-backed tanagers in central Panama. 



Two small finches, Sporophila castaneiventris and Oryzoborus 

 angolensis, were observed in open scrub and grasslands near Iquitos. 

 Neither species occurred in mixed flocks as frequently as some of the 

 Central American species of the same genera. 



Montane birds of the central Andes were studied during two brief 

 visits to Ecuador between August 4 and August 9, 1959, and between 

 May 19 and June 2, i960, on the slopes of Pichincha and Atacazo 

 above Quito, near Quito itself, and near the town of San Antonio 



