NO. 5 THE YELLOW-RUM PED TANAGER — MOYNIHAN 25 



of the wings by male crimson-backed tanagers before copulation. 

 Wing-quivering seems to be obsolescent in yellow-rumped tanagers. 

 It is performed less frequently than in some species of related genera. 

 Perhaps it is on the way to complete disappearance, as it seems to have 

 done already in crimson-backed tangers. 10 



In addition to the possible cases of attempted rape described above, 

 four reactions which may have been unsuccessful copulation attempts 

 were observed. In all four cases an adult male flew to a presumed 

 female uttering Thin Rattles and/or Muffled Rattles as he did so. 

 Once the male hovered over the female's back, apparently attempting 

 to land there. The other times the male landed beside the female. 

 Twice the female responded by assuming a Bill-up Tail-up Posture. 

 When this happened the male retreated at once. (Bill-up Tail-up 

 Postures seem to be part of "soliciting" in many passerines, but they 

 may not encourage copulatory behavior by male yellow-rumped 

 tanagers.) 



When precopulatory behavior is stopped short or cut off abruptly, 

 without leading to actual copulation, male yellow-rumped tanagers 

 tend to perform one or more rapid bill-wiping movements. Similar 

 movements are performed by males of many related species in 

 similar circumstances. This is the sort of reaction which looks, at 

 least superficially, like "displacement." 



DISCUSSION 



Three aspects of the display repertory of yellow-rumped tanagers 

 seem to be particularly significant : 



1. The remarkable resemblance of some of the vocal patterns, 

 especially the Rattle — Hoarse Flourish "complex," to some of the 

 vocalizations of Chlorospingus species. 



10 There are indications that the yellow color of the rump is essentially a non- 

 hostile (perhaps positively sexual) sign stimulus. The contrasting black, or 

 the combination of black with a light bill, may be a hostile sign stimulus. I 

 have seen a wild male yellow-rumped tanager attack an adult male blue-black 

 grassquit (Volatinia jacarind). Adult male blue-black grassquits have almost 

 entirely black plumage and silvery bills. As the individual that was attacked 

 did not seem to be doing anything to provoke hostility, it may have been attacked 

 simply because of its appearance. If so the stimuli releasing attack may be 

 essentially the same in both yellow-rumped tanagers and crimson-backed 

 tanagers. If black is a hostile stimulus in both species, they differ significantly 

 from species of certain other groups of American "nine-primaried" songbirds, 

 e.g. honeycreepers of the tribe Dacnini. (This will be discussed in more detail 

 in a later paper.) 



