NO. 7 FLOCKS OF NEOTROPICAL BIRDS — MOYNIIIAN I33 



below Quito. There is a good deal of bush and scrub in this area, 

 especially on Pichincha and Atacazo ; and much of it is reminiscent of 

 the montane bush on the Volcan de Chiriqui. It is inhabited by a 

 great variety of tanagers, honeycreepers, and finches, many of which 

 have many of the same habits as the members of the montane bush 

 alliances on the Volcan de Chiriqui. Some of these birds are sup- 

 posed to be closely related to species that associate in mixed flocks in 

 Panama. Among them are two species of Thraupis, bonariensis and 

 cyanocephala, and two conspicuous and brightly colored species of 

 Atlapetes, leucoptera and rufinucha, which feed and move through 

 shrubbery in very much the same way as bush-tanagers on the Volcan 

 de Chiriqui. In spite of these resemblances, the tanagers, honey- 

 creepers, and finches of the montane bush near Quito do not seem to 

 form mixed flocks like the mixed flocks of the montane bush alliances 

 on the Volcan de Chiriqui. Individuals of several species frequently 

 occur together when they feed in the same trees or shrubbery in the 

 montane bush near Quito ; but all or most of these associations seem 

 to be purely casual aggregations. Such associations seem to be usually 

 or always brief, and do not appear to be organized in any very regular 

 or definite way. 



These observations would suggest that mixed flocks of tanagers, 

 honeycreepers, and/or finches may really be more common (and may 

 even tend to be more highly organized, on the average) in Central 

 America and southern Brazil than in the Amazonian region or the 

 central Andes. 



The tanagers and honeycreepers are certainly primarily tropical 

 South American groups, at least at the present time. Most of the 

 finches that occur in mixed flocks in Central America also belong to 

 primarily tropical South American groups. Both Central America and 

 southern Brazil seem to be marginal, partly isolated, and relatively 

 unfavorable areas for such groups. The southern Brazilian region 

 verges on the Temperate Zone. The forests of southern Brazil, where 

 the mixed flocks of tanagers, honeycreepers, and finches have been 

 noted, are partly separated from the main body of Amazonian forests 

 at the present time by wide intervening areas of savanna and compara- 

 tively dry scrub (see, for instance, Cruz Lima, 1945, and Darlington, 

 1957). Central America also verges on the Temperate Zone. The 

 tropical forests of Central America are probably less complex, provid- 

 ing fewer habitats, than the forests of the Amazon basin (Holdridge, 

 quoted in Slud, i960). Many birds of primarily North American 

 groups have penetrated into Central America, to a greater or lesser ex- 



