NO. 7 FLOCKS OF NEOTROPICAL BIRDS — MOYNIHAN IOI 



tribute very much to enhance the conspicuousness of the mixed flocks 

 with which they are associated. 



Summer Tanager. — The usual social role of summer tanagers in 

 mixed montane bush flocks on the Volcan de Chiriqui seems to be the 

 same as in the mixed blue and green tanager and honeycreeper flocks 

 of the lowlands of central Panama. 



Pale-vented Thrush. — This large, dull-colored, high montane species 

 tends to have a disruptive effect on mixed montane bush flocks. Pale- 

 vented thrushes seem to be attracted by individuals of many species 

 of the higher-altitude montane bush alliances and/or are attracted to 

 many of the same foods as these latter species ; but they also tend to 

 perform many supplanting attacks upon any and all other passerine 

 birds in their immediate vicinity. Such behavior may be typical of 

 thrushes of the genus Turd us. The few times that clay -colored 

 thrushes were seen associated with mixed blue and green tanager and 

 honeycreeper flocks they also tended to have a disruptive effect on the 

 flocks. 



PARTIAL SUMMARY 



It may be useful to recapitulate briefly and summarize the usual 

 social roles of different species in mixed montane bush flocks in the 

 same terms as in the discussion of the species of mixed blue and green 

 tanager and honeycreeper flocks. 



Both bush-tanagers are regular members of mixed montane bush 

 flocks and essentially passive nuclear species. They are not completely 

 passive, however, and the sooty-capped bush-tanager is less passive 

 than the brown-capped bush-tanager. 



The collared redstart is a regular member of mixed montane 

 bush flocks and apparently always a nuclear species. In some flocks 

 (the "high" flocks) it is a passive nuclear species. In most flocks it 

 is not definitely either passive or active. 



The black-cheeked warbler is rather similar to the collared red- 

 start. It is apparently always a regular nuclear species. It seems to 

 be a passive nuclear species in some flocks and not definitely either 

 passive or active in other flocks. 



Wilson's warbler is a regular active nuclear species. 



The yellow-thighed finch is a regular nuclear species. It may be 

 an active nuclear species or a passive nuclear species, or both, depend- 

 ing upon the identity of the other species associated with it. 



The silver-throated tanager may be an occasional active nuclear 



