8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



inside the forest below the canopy. They come nearest to the ground 

 in certain areas where tall trees are scarce. In such areas they some- 

 times come down to the top of low scrub, no more than a few feet 

 above the ground. They may then be joined by such species as the 

 green-backed sparrow and the dusky-tailed ant-tanager, which usually 

 occur inside low scrub. These low-scrub species usually drop out of 

 mixed blue and green tanager and honeycreeper flocks as soon as the 

 other members of the flocks return to the trees. 



All or most of the members of any given mixed blue and green 

 tanager and honeycreeper flock are usually in approximately the same 

 level of vegetation at any given time. This is one of the more distinc- 

 tive features of such flocks (see below). 



Mixed blue and green tanager and honeycreeper flocks are formed 

 most frequently and are most often large during the nonbreeding 

 season. Birds of many species of the blue and green tanager and 

 honeycreeper alliance tend to associate with individuals of other 

 species of the alliance relatively infrequently during the breeding 

 season, as they adopt territories or (if they already own territories) 

 they spend more and more time in the immediate vicinity of their 

 nests; but they seldom or never stop associating completely. Every 

 once in a while during the breeding season a mixed blue and green 

 tanager and honeycreeper flock will be formed which is quite as large 

 and complex as any formed during the nonbreeding season. 



Mixed blue and green tanager and honeycreeper flocks are not very 

 stable in any circumstances. Associations between individuals of 

 different species of the blue and green tanager and honeycreeper 

 alliance tend to be brief and are very seldom or never sustained con- 

 tinuously over a whole day. The composition of mixed blue and green 

 tanager and honeycreeper flocks is also extremely variable, almost 

 from minute to minute. Birds of different species are constantly 

 coming together, staying together for a brief period, and then becom- 

 ing separated again as some move on (perhaps going a considerable 

 distance away) and others do not. 



In spite of this short-term variability, it is quite obvious that the 

 same birds of the same species tend to come together again and again. 

 In favorable habitats (see below) the same birds of the same species 

 may rejoin one another a dozen times a day and will certainly rejoin 

 one another day after day for periods of at least several months. 



None of the species of the blue and green tanager and honeycreeper 

 alliance seems to have any special behavior patterns whose main func- 

 tion is to attract individuals of other species. In many or most cases, 



