NO. 7 FLOCKS OF NEOTROPICAL BIRDS — MOYNIHAN 7 



of flycatchers (especially the yellow-bellied elaenia, Elaenia flavo- 

 gaster, the social flycatcher, Myiosetetes similis, and the rusty- 

 margined flycatcher, M. cayanensis) , and several different types of 

 vireos and cotingas. 



There are also some species, including the green-backed sparrow 

 (Arremonops conirostris), the dusky-tailed ant-tanager (Habia fusci- 

 cauda), the blue-black grassquit {Volatinia jacarina), the variable 

 seedeater {Sporophila aurita), and the yellow-bellied seedeater (S. 

 nigricollis) , that are associated with blue and green tanager and honey- 

 creeper flocks in some circumstances, but are usually more or less 

 distinctly separated by habitat preference (see below). 



Finally, there are some species, such as hummingbirds, woodpeckers, 

 and the Tovi parakeet (Brotogeris jugnlaris), that are not infre- 

 quently found in close physical proximity to blue and green tanager 

 and honeycreeper flocks, but still appear to be essentially independent 

 of such flocks, as their movements are seldom or never coordinated 

 with those of the flocks. 



DESCRIPTION OF THE FLOCKS 



Mixed blue and green tanager and honeycreeper flocks are very 

 widely distributed in central Panama, but they are most characteristic 

 of lowland areas. Some of the species of what may be called the 

 "blue and green tanager and honeycreeper alliance" 2 seem to be abso- 

 lutely confined to the lowlands. Other species of the alliance occur 

 in both lowland and highland areas. I have seen some of them near 

 the peaks of the highest mountains in central Panama, around 3,200- 

 3,400 feet above sea level, and even higher in western Panama (see 

 below) ; but all or most of them are more common in the lowlands 

 than in the mountains. I have never seen large typical mixed blue 

 and green tanager and honeycreeper flocks above 2,000 feet elevation 

 in central Panama. 



Most of the species that occur in mixed blue and green tanager 

 and honeycreeper flocks are essentially arboreal, and all the species 

 that are regular members of such flocks are primarily "edge" birds. 

 Most of them also prefer to remain as high above the ground as 

 possible. Typical mixed blue and green tanager and honeycreeper 

 flocks usually stay in or near the treetops, and never occur very far 



2 The term "alliance" will be used throughout this paper to include all the 

 species that are regular members (see below) of a particular type of mixed flock, 

 plus any other species that occur in that particular type of mixed flock relatively 

 frequently. 



