NO. 7 FLOCKS OF NEOTROPICAL BIRDS — MOYNIHAN 125 



mimicry, in other words, will tend to make a flock a closed society. 

 It is probably significant that the largest mixed flocks of small finches 

 in Panama, in which social mimicry seems to be most highly developed, 

 include fewer species than many mixed blue and green tanager and 

 honeycreeper flocks and mixed montane bush flocks. 



THE DISTRIBUTION OF MIXED FLOCKS AND THE SPECIES 

 INCORPORATED IN SUCH FLOCKS 



There seems to be a general correlation between the social roles 

 and the geographical distribution of many tanagers and finches and 

 some other birds that are regular members of mixed flocks in tropical 

 America. This correlation is clear in the case of the species of the 

 mixed blue and green tanager and honeycreeper flocks. The plain- 

 colored tanager, which is much the most important passive nuclear 

 species in fully-developed blue and green tanager and honeycreeper 

 flocks, has by far the most restricted distribution of any of the regu- 

 lar members of such flocks. It is confined to the lowlands of Colom- 

 bia, Panama, and Costa Rica. 19 This is appreciably smaller than the 

 range of the golden-masked tanager, which is probably closely related 

 to the plain-colored tanager (the two species share a number of char- 

 acters that are not found in other Panamanian species of Tangara), 

 and occurs in many of the same habitats in Panama, but is apparently 

 an active nuclear species in mixed blue and green tanager and honey- 

 creeper flocks. Various subspecies of the golden-masked tanager ex- 

 tend from western Ecuador to southeastern Mexico. (Hellmayr, 

 1936, includes the form nigro-cincta m the same species; but this has 

 been questioned by Eisenmann, 1957. If larvata and nigro-cincta are 

 really conspecific, then the range of the species also extends over most 

 of tropical eastern South America.) All the other, more important, 

 active nuclear species among the more common regular members of 

 the mixed blue and green tanager and honeycreeper flocks, i.e., the 

 palm tanager, the blue tanager, and the green honeycreeper, are at 

 least as widely distributed as the golden-masked tanager, extending 

 over all or most of the lowlands of tropical Central and South 

 America. 



Similar mixed flocks of tanagers and honeycreepers occur in the 



19 Unless stated otherwise, these and the following summaries of the ranges 

 of different species are based upon Hellmayr, 1925 (furnariids), 1935 (vireos, 

 warblers, and honeycreepers), 1936 (tanagers), and 1938 (finches). 



Hellmayr states that the plain-colored tanager is confined to Colombia and 

 Panama; but it has been found in northeastern Costa Rica by Slud (i960). 



