94 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



though they may come down to low shrubbery from time to time. They 

 are very inconspicuous birds, not very brightly colored, usually very 

 quiet, and not very gregarious among themselves. Single birds, pairs, 

 and family groups of this species are usually found widely separated 

 from one another, and are probably territorial. 



Red- faced spinetails are joined and followed by individuals of 

 other species very rarely, but they join and follow individuals of 

 other species very frequently. They seem to be particularly strongly 

 attracted to brown-capped bush-tanagers, and tend to join them (at 

 least when the latter are in trees) much more frequently than they 

 follow them (using the terms "join" and "follow" as denned above). 

 I have seen the same pair of red- faced spinetails join the same flock 

 of brown-capped bush-tanagers repeatedly over a period of several 

 hours every morning for seven successive days. 



Brief observations of other furnariids on the Volcan de Chiriqui 

 would suggest that ail or most of them are similar to red-faced spine- 

 tails insofar as they tend to join and follow individuals of other species 

 more frequently than they themselves are joined and followed. All or 

 most of them probably also tend to join more frequently than follow. 



All these species are primarily or exclusively insectivorous. Some 

 of them, such as the tree-creepers and the ruddy tree-runners, usually 

 or always feed on insects they find in or on the bark of trees. Such 

 species do not seem to derive much benefit in the way of food from 

 their associations with mixed flocks. They do not usually feed on 

 insects stirred up by other members of the flocks. 



SILVER-THROATED TANAGER 



On the western slopes of the Volcan de Chiriqui, silver-throated 

 tanagers are rather common slightly above 5,000 feet, and extend in 

 decreasing numbers up to at least 6,000 feet. In this area they are 

 sometimes associated with mixed montane bush flocks, but they do 

 not seem to be regular members of such flocks, and sometimes de- 

 liberately refrain from joining them. When they do associate with 

 mixed flocks they are seldom or never closely integrated with the 

 other members of the flocks. They are essentially birds of the treetops, 

 although they do come down to low shrubbery, almost to the ground, 

 occasionally ; and they seem to be more strongly attracted to the very 

 heterogeneous lower-altitude mixed flocks, which usually include many 

 other arboreal species, than to the less heterogeneous higher-altitude 

 flocks, which usually include a large proportion of thicket-inhabiting 

 birds. They seem to join and follow individuals of all or most other 



