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January 15 
Barro 
<* 
1958, 
dorado. 
THE GRHjARIOUSNESS OF THE PIAIN TANAGER, AND ITS POSSIBLE ROLE IN MIXED FLOCKS, 
The Plain Manager is the most remarkable tanager around here. 
It can be distinguished from all its local relatives by several characters, i,e, 
its dull and simple color pattern, its extreme gregariousness, its extreme restlessness 
and mobility, and the extreme frequency and rapidity of its Call Notes, 
The color pattern is quite unlike that of most other tanager# and honey cr eepers 
(even the most emberizine-like forms); but it is not very cryptic, (Female Green 
Honeycreepers and Dacnis are probably less conspicuous in the tree-tops than Plain 
Tanagers,) 
The restlessness is peculiar, insofar as a flock will often leave a desirable 
food source (e,g, Cecropia) before the food is exhausted, fly to another source 
(e,g, another Cecropia) which is essentially identical with the first, and then return 
to the first source again. All this in a matter of minutes. The Plain Tanagers often 
seem to move just because they ’’like” moving — — when it isn*t really ’’necessary*’ from 
a practicalpoint of view. 
The restlessness and the ” exaggerated’’ Call Notes (and the bright wing-patch) all 
seem to be ’’designed” to induce, i.e, take advantage of, the "following response" of 
other birds. 
These characters must help to maintain the cohesion of a flock gf Plain Tanagers* 
but they may also help to attract birds of other, species, keeping them in the vicinity 
of the Plain Managers, (If it is advantageous for the Plain Tanagers to aggregate in 
groups — - as it obviously must be — then it may well be advantageous for them to 
increase the effective size of their flock by attracting all the other birds of roughly 
similar feeding habits in the neighborhood,) 
Blue and Palm Tanagers (whose coloration is also comparatively dull and simple) 
may become ’’integral" members of a r lain Tanager flock. Blue Honeycreepers and 
Ultramarine Dacnis may follow a flock. Other species, including the Green Honeycreeper , 
the Scarlet-thighed Dacnis, the Golden-maned Tanager, and at least one species of oriole, 
may hang around in the vicinity of a flock. 
It should be noted that almost all the birds more or less closely associated with 
the Plain T anagers here are largely blue and/or green (usually with some black), and 
that many of them are brighter or more intricately patterned than the Plain Tanagers, 
This might suggest that the peculiar coloration of the Plain Tanager has been evolved 
because it is more or less "neutral". It can*t look too "strange" to the other species; 
but it is still quite distinct. It won't provoke escape* nor will it release sexual 
or aggressive responses. 
(It is possible that the Blue- and Palm Tanagers have evolved in the same direction 
as the Plain Tanager; but they seem to be less specialized,) 
