NO. 7 FLOCKS OF NEOTROPICAL BIRDS — MOYNIHAN JJ 



the mixed blue and green tanager and honeycreeper flocks, they seem 

 to be formed more frequently and include more birds of more species, 

 on the average, during the nonbreeding season than during the breed- 

 ing season. They are also more common and tend to be larger in the 

 early morning than at other times of the day. 



Many of the higher-altitude mixed montane bush flocks seem to 

 have definite ranges, and tend to move through their ranges along 

 definite and rather stereotyped pathways. They tend to visit the same 

 sites in more or less the same sequence again and again on the same 

 day and on successive days. 



Some of the members of the higher-altitude montane bush alliances 

 seem to be purely insectivorous, but others eat fruits and seeds as well 

 as insects. All spend most of their time feeding while they remain 

 in the flocks. As in the case of the members of the blue and green 

 tanager and honeycreeper alliance, however, it is obvious that indi- 

 viduals of different species of the higher-altitude montane bush al- 

 liances are sometimes attracted to one another by some social factor 

 or factors in addition to, or instead of, the direct stimulus of food 

 (see below). It was my impression, in fact, that members of the 

 higher-altitude montane bush alliances are attracted to one another 

 by purely social factors, apart from food, more frequently than are 

 members of the blue and green tanager and honeycreeper alliance. 



Unlike the members of most blue and green tanager and honey- 

 creeper flocks, the members of most higher-altitude mixed montane 

 bush flocks are frequently scattered through many different levels of 

 vegetation. It is very common to see higher-altitude mixed montane 

 bush flocks that include some birds feeding and moving on or near 

 the ground, other birds feeding and moving in moderately low shrub- 

 bery, and still others feeding and moving in the treetops, all at the 

 same time. 



(Some of the mixed montane bush flocks above 6,000 feet on the 

 Volcan de Chiriqui appeared to be accompanied by one, two, or three 

 squirrels (probably Sciurus granatensis) , 13 The associations between 

 these squirrels and the mixed bird flocks were not very close, as the 

 squirrels were always, or almost always, several feet away from the 

 nearest birds; but the squirrels occurred in the general vicinity of 

 mixed flocks more frequently than would seem likely by chance alone. 



It may be significant, in this connection, that these squirrels are 

 noisy animals, frequently uttering sharp chattering calls that are 



13 I am indebted to Dr. Charles O. Handley, Jr. (in litt.), for the probable 

 identification of these squirrels. 



