102 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



species on the Volcan de Chiriqui. The slate-throated redstart may 

 be an occasional nuclear species, but not definitely either passive or 

 active. 



The brown-capped vireo and some or all of the furnariids associ- 

 ated with mixed montane bush flocks seem to be regular attendant 

 species. The yellow-throated bush-finch is probably a regular at- 

 tendant in flocks that include yellow-thighed finches, but an occasional 

 attendant (at best) in other mixed flocks. The summer tanager seems 

 to be an occasional attendant species in all types of mixed montane 

 bush flocks. 



It will be noted that many of the species of the montane bush alli- 

 ances are more difficult to assign to discrete categories, according to 

 their social roles in mixed flocks, than are the species of the mixed 

 blue and green tanager and honeycreeper alliance. The significance 

 of this difficulty will be discussed below. 



Diagram 3 is a tentative summary of the special interspecific prefer- 

 ences of the most common species of the higher-altitude montane bush 

 alliances revealed by predominantly "friendly" following and/or join- 

 ing reactions. It should be compared with the summary of the cor- 

 responding preferences of species of the blue and green tanager and 

 honeycreeper alliances shown in diagram 1. 



THE COLORS OF SPECIES IN MIXED MONTANE BUSH FLOCKS 



There is only a restricted range of colors in the plumages of almost 

 all the species commonly occurring in the higher-altitude mixed mon- 

 tane bush flocks and the majority of the species commonly occurring in 

 the lower-altitude mixed montane bush flocks on the Volcan de Chi- 

 riqui. The plumages of these species are largely black and/or yellow 

 (including yellow-olive), sometimes variegated with patches of brown 

 and/or white. Bright greens, blues, and reds are lacking in the plum- 

 ages of most of these species, and confined to small patches in the 

 plumages of the others. 



This general similarity of coloring may be adaptive in any one or 

 all of several different ways. In any case, it probably tends to facili- 

 tate associations between individuals of different species. The birds 

 of these species must become conditioned fairly early in their lives to 

 the presence of companions that are predominantly black and/or yel- 

 low, with or without patches of brown and/or white. Some or all 

 of these species may even be born with an innate recognition or 

 preference for one or more of these colors. Thus an individual of 

 any species exhibiting one or more of these colors is probably more 



