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on in this region as a whole. Possibly [[underline]]slightly[[/underline]] less common than in the Munchique region as a whole. But flocks do seem to be more common around 9000 ft here than at the same elevation on Munchique. (This comparison may not be entirely fair, however, in view of the small extent of high altitude areas on Munchique.)
It might be added, in this connection, that the frequency of mixed flocks here is matched by the frequency of mixed flocks seen at lower elevation in the northern part of the Central Cordillera a couple of years ago Extreme Allow-gregariousness would appear to be characteristic of the Central Cordillera as a whole!!!
How does this help me with my various hypotheses?
The development of mixed flocks might be positively correlated with any one or all of a great variety of factors.
(1). Number of species in region.
(2). Age of region.
(3). Humidity of region - and density of vegetation.
(4). Isolation of region.
(5). Size of region - and relative extent of frontiers.
(6). Accessibility of region to invasion from outside, by "is level-hopping".
Possibility (1) may be discounted. Because flocks are common in Bolivia, although the number of species there is only half of what it is in any one of the three cordilleras of Colombia.
Possibility (2) may be discounted because there is no [[underline]]continuous[[/underline]] trend in the development of mixed flocks from South to North throughout the Andes. (The trend is "reversed" in the middle. No
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