104 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



Blue tanagers occur up to 6,000 feet on the western slopes of the 

 Volcan de Chiriqui. They may not have occurred at such high alti- 

 tudes before much of the original montane forest was cut ; but they 

 seem to be well established along roads and around the town of Cerro 

 Punta now. These blue tanagers frequently occur in the same gen- 

 eral areas, even in the same trees, as species that are regular members 

 of the mixed montane bush flocks, and they seem to feed on many 

 of the same insects and fruits as some of the species that are regular 

 members of the mixed montane bush flocks ; but they do not usually 

 associate with mixed montane bush flocks. They join the very hetero- 

 geneous lower-altitude mixed montane bush flocks occasionally, but 

 they almost always keep strictly apart from the more closely integrated 

 higher-altitude mixed flocks. This seems to be the result of definite 

 choice. I have seen blue tanagers watch higher-altitude mixed mon- 

 tane bush flocks only a few yards away without showing the slightest 

 indication of a desire to approach the flocks more closely or to follow 

 individuals of any species in the flocks. Similarly, none of the birds 

 in these higher-altitude mixed flocks showed any tendency to join 

 and/or follow the blue tanagers. 



The blue tanagers of the Volcan de Chiriqui belong to the same 

 subspecies as the blue tanagers of the lowlands of central Panama 

 and behave in the same way apart from mixed species flocks. There 

 is no reason to suppose that they do not have the same internal gregari- 

 ous tendencies as the blue tanagers of the lowlands, which join and 

 follow individuals of other species so frequently (see also below). 

 It seems likely, therefore, that the usual lack of response by the blue 

 tanagers of the Volcan de Chiriqui to the mixed flocks they encounter 

 is largely or completely due to the characteristic coloration of all or 

 most of the individuals in the flocks, a coloration that either fails to 

 attract or actually repels (see below) the blue tanager. Many of 

 the species in mixed montane bush flocks are not more different from 

 blue tanagers in shape or behavior than many of the species that blue 

 tanagers join and follow relatively frequently in the lowlands. 



A few brief observations would suggest that the blue tanagers of 

 the Volcan de Chiriqui are more strongly attracted to bay-headed 

 tanagers (Tangara gyrola), which occur in small numbers slightly 

 above 5,000 feet, than to any of the other species discussed above. It 

 is surely not coincidental, in this connection, that bay-headed tanagers 

 are largely bright blue and green and also tend to join mixed mon- 

 tane bush flocks relatively rarely. (The reactions of the blue tanagers 

 of the Volcan de Chiriqui to bay-headed tanagers is positive evidence 



