46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



Palm tanagers also tend to perform more supplanting attacks upon 

 individuals of other species than do any other tanagers of the blue 

 and green tanager and honeycreeper alliance. These supplanting 

 attacks do not, however, disturb the mixed flocks very greatly, as the 

 supplanted individuals seldom fly very far away. 



The relationships between palm tanagers and the other species of 

 the blue and green tanager and honeycreeper alliance can be divided 

 into two main types. 



The reactions of palm tanagers to individuals of most other species 

 seem to be nothing more than expressions of generalized gregarious- 

 ness (or equally nonspecific hostility, in some cases). They do not 

 seem to react to most other species unusually frequently or strongly. 



The reactions of palm tanagers to plain-colored tanagers and blue 

 tanagers seem to be much more specialized. Palm tanagers join, 

 follow, and supplant plain-colored tanagers and blue tanagers 8 much 

 more frequently than they join, follow, and supplant individuals of 

 any other species in apparently similar social circumstances, i.e., when 

 they are equally close to plain-colored tanagers, blue tanagers, and 

 individuals of other species, and when these species seem to be approx- 

 imately equally noisy and conspicuous. Palm tanagers also join, fol- 

 low, and supplant plain-colored tanagers and blue tanagers much 

 more frequently than do individuals of other species in similar social 

 circumstances. These reactions would seem to be too frequent to be 

 expressions of generalized gregariousness alone : they seem to be 

 expressions of stronger social bonds, which might be called "special 

 interspecific preferences." 



As a rough generalization, it can be said that palm tanagers usually 

 show a strong special interspecific preference for plain-colored tana- 

 gers, and a weaker special interspecific preference for blue tanagers ; 

 but both these preferences are rather variable, and tend to be much 

 more obvious during some types of social reactions than during others. 



In most circumstances, palm tanagers seem to join and follow plain- 

 colored tanagers almost as frequently as they join and follow all or 

 most other members of their own species (perhaps more frequently 

 in many cases). They may also supplant plain-colored tanagers more 

 frequently than they do other palm tanagers. 



The relatively great frequency of supplanting attacks by palm tana- 

 gers upon plain-colored tanagers is not an indication that the former 



8 It should be stressed, again, that this discussion is an analysis of the beha- 

 vior of species in central Panama. The reactions of palm tanagers to blue 

 tanagers may be different in parts of South America (see below). 



