NO. 7 FLOCKS OF NEOTROPICAL BIRDS — MOYNIHAN 49 



There may be several reasons for this. Palm tanagers are among the 

 largest birds of the blue and green tanager and honeycreeper alliance 

 and are probably more intimidating than such smaller species as the 

 plain-colored tanager and the red-legged blue honeycreeper (see 

 below). In many cases, moreover, individuals of other species are 

 not able to join or follow palm tanagers before the palm tanagers have 

 joined or followed them. 



The dull plumage of palm tanagers may be neutral in more or less 

 the same way as the similar plumage of plain-colored tanagers. It may 

 be an adaptation to increase the frequency with which palm tanagers 

 are approached by individuals of many other species probably permit- 

 ting them to be approached more frequently than they would be if they 

 were more brightly colored (unless the bright coloration were of a 

 very special type — see below). The plumage of palm tanagers is prob- 

 ably not an adaptation to facilitate their associations with plain-col- 

 ored tanagers alone. Palm tanagers are much more widely distributed 

 than plain-colored tanagers (see below). 



The social tendencies of palm tanagers are probably essentially the 

 same in all environments ; but they may fail to be expressed by overt 

 behavior under certain conditions. 



As their name would imply, palm tanagers show a definite prefer- 

 ence for palm trees, nesting in the tree crowns or, less frequently, in 

 other tall trees of similar shape, with dense crowns and bare trunks. 

 They may also show a preference for manmade structures that have 

 some of the same characteristics as palm trees. Near Frijoles, for 

 instance, they were greatly attracted to the pylons along the railroad 

 track, and some may have nested in the tops of these. Even when 

 they nested in adjacent trees, many of the palm tanagers at Frijoles 

 spent much of their time resting in the pylons. 



Palm tanagers that have selected palm trees or similar trees or 

 similar manmade structures as nesting sites are often reluctant to 

 leave the vicinity of such sites during the whole period immediately 

 before, during, and immediately after the breeding season. Other 

 members of the blue and green tanager and honeycreeper alliance 

 are equally reluctant to visit such trees or structures if they are far 

 from other trees. 



Thus, palm tanagers that select isolated trees or structures as nest- 

 ing sites also tend to be isolated socially. They do not encounter other 

 members of the blue and green tanager and honeycreeper alliance very 

 frequently and usually do not follow other birds very far even when 

 they do meet them. Such palm tanagers cannot play their usual role 



