32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



genera are very similar to the corresponding displays of Ramphocelus 

 species in form, function, and causation. 



3. In view of these similarities between Ramphocelus species and 

 species of other genera, it is perhaps remarkable that there are so 

 many differences between the yellow-rumped tanager and the crimson- 

 backed tanager. The display behavior of the yellow-rumped 

 tanager, as a whole, seems to be as much like that of the brown-capped 

 bush-tanager as like that of the crimson-backed tanager, while the 

 display behavior of the crimson-backed tanager seems to be as much 

 like that of Tachyphonus rufus as like that of the yellow-rumped 

 tanager. (The behavior of Tachyphonus species will be discussed in 

 a later paper.) 



Comparable contrasts are found within other genera, e.g. Saltator, 

 Cyanerpes, and Diglossa. It does, in fact, seem to be characteristic 

 of many groups of American "nine-primaried" songbirds that the 

 differences between the display repertories of different species of the 

 same genus are at least as great as the differences between their 

 repertories and those of some species of other genera. 



4. The differences between the purely or predominantly sexual 

 displays of yellow-rumped tanagers and crimson-backed tanagers are 

 not greater than the differences between some of their other displays. 

 Some of the patterns apparently used by males to attract mates, e.g. 

 some Dawn Calling notes, are actually quite similar in the two species. 

 This would suggest that much of the divergence between the display 

 repertories of these two sympatric species is not primarily, or not 

 only, an adaptation to maintain reproductive isolation between them. 



ACKNOWLEDGMENTS 



This report is part of a project supported by the National Science 

 Foundation (NSF G 5523). 



I am grateful to Mr. William G. Conway for facilitating observa- 

 tions of captive birds in the New York Zoo, and to Dr. Philip 

 Humphrey and Mr. Eugene Eisenmann for checking specimens in 

 the United States National Museum and the American Museum of 

 Natural History. 



SUMMARY 



This is primarily a study of the behavior of yellow-rumped 

 tanagers {Ramphocelus flammigerus icteronotus) observed under 

 natural conditions in Panama. 



