IOO SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



able time in the tall trees. The birds high in trees may form mixed 

 flocks that are independent of mixed flocks in the shrubbery at the 

 same time. The higher and lower flocks may move in different direc- 

 tions. The high flocks are usually composed of one or two collared 

 redstarts and one Wilson's warbler, plus a few birds of other species, 

 such as flame-throated warblers, furnariids, and slate-throated red- 

 starts (if present in the area). These high flocks apparently never 

 include yellow-thighed finches or black-cheeked warblers, and seldom 

 include sooty-capped bush-tanagers. The collared redstarts are usually 

 the real leaders of the high flocks, as all, or almost all, the other mem- 

 bers of the high flocks usually tend to follow the collared redstarts 

 directly. 



It should be stressed, however, that such high flocks are relatively 

 rare and more or less atypical. All, or almost all, the birds in the high 

 flocks in this area also go down to the shrubbery more or less fre- 

 quently, where they tend to associate with more typical mixed montane 

 bush flocks that include yellow-thighed finches and black-cheeked 

 warblers. In other areas at the same elevation where the same species 

 of birds occur but the vegetation is not divided into two distinctly 

 separated strata, the birds are seldom or never divided among higher 

 and lower flocks moving independently of one another.) 



OTHER SPECIES 



Flame-throated Warbler. — I did not see flame-throated warblers 

 very frequently on the Volcan de Giiriqui and was not able to analyze 

 their usual social role in mixed flocks. All I can say about them is 

 that they are very conspicuous (both brightly colored and noisy), 

 found around 6,000 feet and above, apparently usually or always ter- 

 ritorial, more common in trees than in low shrubbery, and probably 

 join and follow individuals of other species (at least collared red- 

 starts) more frequently than they are joined and followed by indi- 

 viduals of other species. 



Brown-capped Vireo. — Brown-capped Vireos were observed only 

 at 6,000 feet and above on the Volcan de Chiriqui. In this area they 

 are frequently associated with mixed montane bush flocks, especially 

 flocks in trees of moderate height. They seem to join individuals of 

 other species more frequently than they follow or are followed or 

 joined by individuals of other species. They do not seem to exhibit 

 any special interspecific preferences. They are very inconspicuous and 

 not very gregarious among themselves, and so probably do not con- 



