26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 149 



The similarities are extensive and detailed enough to suggest that 

 Ramphocelus and Chloraspingus are closely related to one another. 



The two genera are kept far apart from one another in current 

 classifications and checklists, e.g. Hellmayr, 1936; but the differ- 

 ences between them, e.g. in bill shape, body proportions, and the 

 absence of bright plumage in males of Chlorospingus, may be nothing 

 more than superficial adaptations to particular habitat preferences and 

 feeding methods. 



2. The large number of different types of display. 



Two general features seem to be characteristic of the display 

 behavior of many highly gregarious species of the American "nine- 

 primaried" songbird group, and probably many other groups as 

 well (see Moynihan, 1960 and 1963). Highly gregarious species 

 seem to express a larger proportion of their hostility by means of 

 display, and a smaller proportion by overt unritualized activity, than 

 do less gregarious species. They also, in many cases, have fewer 

 recognizably distinct types of partly or purely hostile displays or 

 partly independent components of displays than less gregarious spe- 

 cies. (As the great majority of displays in all species are at least 

 partly hostile, this latter statement means, in fact, that highly gregar- 

 ious species tend to have a lesser total number of types of display 

 than less gregarious species.) 



The highly gregarious yellow-rumped tanagers seem to conform 

 to the first of these general rules but not to the second. They do 

 express a very large proportion of their hostility by display. (It is 

 noticeable, for instance, that they relatively seldom perform overt at- 

 tack and escape movements without also performing some display, 

 usually vocal, at the same time.) They do not, however, have a rela- 

 tively small number of different types of display. They certainly have 

 many more different types of display than such extremely gregarious 

 species as the plain-colored tanager, Tangara inornata (personal obser- 

 vation). They even have more different types of display than the 

 moderately gregarious and closely related crimson-backed tanagers. 

 They seem, in fact, to have at least as many different types of 

 display and partly independent components of displays as the very 

 slightly gregarious green-backed sparrow (which seems to be as 

 nearly completely nongregarious as any species of neotropical tanager 

 or finch). 11 



11 The variety of different signals in the repertory of yellow-rumped tanagers 

 is even greater than would be suggested by the number of different components 

 alone. This is because the different components can be combined in a rather 



