22 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



hostile display. This was seen only during one prolonged territorial 

 dispute between two adult males. One of the males repeatedly sup- 

 planted the other. Between supplanting attacks the aggressive male 

 adopted a distinctive and presumably ritualized Head-down Posture. 

 The usual form of this pattern is shown in figure 6c. The head was 

 lowered and the neck stretched forward while the bill was pointed 

 diagonally downward. This was accompanied by a moderate amount 

 of Back-ruffling, with the usual drooping of the wings. The tail was 

 lowered but apparently not fanned. The feathers of the head may 

 have been raised, at least occasionally, but apparently never to an 

 extreme degree. Every once in a while the tail was suddenly raised 

 to the position shown in figure 6b, but this may have been nothing 

 more than a balancing reaction. Both the Head-down Postures and 

 the supplanting attacks were accompanied by many rattling patterns, 

 usually or always Thin Rattles. This Head-down Posture is one of the 

 more peculiar patterns of the species. It is rather different from any- 

 thing observed in other species of Ramphocelus or other genera of 

 supposedly closely related tanagers. It may resemble certain patterns of 

 "emberizine" finches (Andrew, 1961), but the evidence is insufficient 

 to determine if it is partly or wholly homologous with the latter or if 

 it has evolved (as a social signal) independently. 



The copulatory patterns and associated or related reactions of 

 yellow-rumped tanagers were observed in only one area, near the 

 mouth of the Rio Piedras on the Atlantic coast, in February and 

 March of 1962. They were not studied at length simply because they 

 were relatively rare and performed less frequently than hostile or 

 other sexual reactions. (This seems to be characteristic of almost all 

 the tropical members of the American "nine-primaried" songbird 

 group). 



Among the most conspicuous reactions of the species is Pouncing. 

 It was observed five times. In each case an adult male which had 

 been sitting on a high perch or flying high above the ground 

 suddenly swooped down at a bird in adult female or juvenal plumage. 

 (The males involved were different in each case. I am almost certain 

 that all the birds that were swooped at were adult females. As far as 

 I could tell there were no birds in the area at the time which per- 

 formed typical juvenile behavior patterns.) In four out of the five 

 cases the bird that was swooped at was flying, in an apparently 

 unritualized manner. In the other case it was perched quietly in low 

 scrub. In all cases the swooping male uttered rattling noises during 

 the descent. All males uttered Thin Rattles; several uttered pure 



