74 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I43 



throated redstart in appearance, but with yellow cheeks and chin and a 

 black breast band. 



Resident in Panama. Common along the edges of forest and scrub. 

 Most common at slightly higher altitude than those at which the slate- 

 throated redstart is most common. Occurs in all levels of vegetation. 



Moderately gregarious apart from mixed species flocks. Very 

 active and restless. Not very noisy. 



Several other species are certainly associated with montane bush 

 flocks at least moderately frequently. Among these are the summer 

 tanager, the speckled tanager {Tangara chrysophrys) , the golden- 

 crowned warbler (Basileuterus culicivorus), the flame-throated war- 

 bler (Vermivora gutturalis), the brown-capped vireo (Vireo leuco- 

 phrys), the blue-throated toucanet (Anlacorhynchus caeruleogularis) , 

 the pale-vented thrush (Turdus obsoletus), and various tyrannid fly- 

 catchers. Some of these species may play important roles in some 

 montane bush flocks (see below) ; but they were either relatively rare 

 in the areas where mixed montane bush flocks were studied most 

 intensively and/or are associated with mixed montane bush flocks 

 much less regularly or less closely than such species as the Chloro- 

 spingus tanagers and the yellow-thighed finch. 



DESCRIPTION OF THE FLOCKS 



The general social organization of most mixed montane bush flocks 

 is similar to that of most blue and green tanager and honeycreeper 

 flocks in the lowlands, but by no means absolutely identical. 



Mixed montane bush flocks are more varied than blue and green 

 tanager and honeycreeper flocks. They include different species at 

 different altitudes. Some species of the montane bush alliances seem 

 to be confined to a rather narrow range of altitudes. Other species 

 occur over a wider range of altitudes but are not equally common 

 throughout their ranges. 



At relatively low altitudes, i.e., around 4,500-5,200 feet on the west- 

 ern slopes of the Volcan de Chiriqui, the montane bush flocks tend to 

 include more species than the corresponding flocks at higher altitudes, 

 and are rather distinctive in some other ways. These comparatively 

 low-altitude flocks will be discussed below, after the discussion of the 

 higher-altitude flocks. 



The brown-capped bush-tanager, the yellow-thighed finch, the slate- 

 throated redstart, various furnariids, and (sometimes) Wilson's war- 

 bler are usually the most conspicuous species in mixed bush flocks 

 from approximately 5,200 to 6,800 feet on the western slopes of the 



