NO. 7 FLOCKS OF NEOTROPICAL BIRDS — MOYNIHAN 21 



hostility ; 4 but overt interspecific hostility was not really rare in the 

 mixed blue and green tanager and honeycreeper flocks on Barro Colo- 

 rado. No interspecific contact fights, actual bill-to-bill or body-to-body 

 struggles, were seen during the periods the flocks were studied inten- 

 sively; but so-called supplanting attacks (see Hinde, 1952) were 

 quite frequent. A supplanting attack may be said to occur when one 

 bird flies to the spot where another bird is perched, and the other 

 bird moves away immediately. Supplanting attacks may intergrade 



Table 6. — Data from observations in and around the clearing on Barro Colorado 

 Island between October 26 and December 20, 1939 



Interspecific supplanting attacks by tanagers and honeycreepers. (No finches 

 or warblers were seen to perform interspecific supplanting attacks in this 

 area during this period of observation.) 



No. of 



cases seen Species supplanting Species being supplanted 



I Plain-colored tanager Golden-masked tanager 



1 do. Green honeycreeper 



1 do. Red-legged blue honeycreeper 



1 do. Crimson-backed tanager 



1 do. Bananaquit 



25 Palm tanager Plain-colored tanager 



2 do. Blue tanager 



11 Blue tanager Plain-colored tanager 



1 do. Palm tanager 



1 do. Fulvous-vented euphonia 



1 Green honeycreeper Plain-colored tanager 



1 do. Shining honeycreeper 



2 Crimson-backed tanager Blue tanager 



49 



with joining attempts, but the difference between the two types of 

 reactions is usually clear. Some of the supplanting attacks in the 

 mixed flocks on Barro Colorado Island were accompanied by forward 

 pecking or jabbing movements, obviously aggressive, by the attacking 

 birds. 



Table 6 is a partial list of the interspecific supplanting attacks 

 observed on Barro Colorado Island between October 26 and Decem- 

 ber 20. This table is organized according to the same principles as 

 the tables immediately preceding. Only those reactions are shown in 



4 The term "hostility" will be used throughout this paper to include all overt 

 attack and escape behavior, as well as all reactions that seem to be produced 

 by the interaction of attack and escape tendencies. 



