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Mixed Diglossini, May 17, 1965, VII.  (43)

the semi-desert which comes close, geographically, to Mérida)

^[[Gen]] This suggests a general principle to me. It is my impression that, throughout the Andes, areas which are relatively humid have more hummingbirds and fewer Diglossini than similar-looking areas (with similar "physiognomy" of vegetation) that are relatively less humid. Hummingbirds seem to "take the place" of Diglossini in very humid areas. They may drive out the Diglossini and/or move in to fill the niche left vacant because most Diglossini cannot survive in a very humid environment.

^[[Gen Albi Cy]] (I think the former alternative is more plausible. Note that the two Diglossini which seem to be most common in very humid environments, the Albi and the Cy, are the two species which would be expected to encounter and/or compete with hummingbirds least frequently. Albis are "skulkers", usually staying [[underlined]] inside [[/underlined]] low scrub - a type of environment which many hummingbirds seem to avoid. And Cys are, on the whole, relatively strongly frugivorous and relatively weakly insectivorous and nectarivorous.)

^[[Gen]] If hummingbirds do drive Diglossini out from relatively humid areas, this might help to explain why Diglossini are so rare in the southern part of the Western Cordillera of Colombia.

^[[Gen]] (But competition with hummingbirds, by itself, probably is not sufficient to explain all variations in distribution and social behavior of Diglossini in other parts of the Andes. It probably will still be necessary to invoke such factors as density of vegetation - quite apart from humidity - and size of regions in which populations occur. Viz Bolivia where populations of Diglossini seem to be dense, and hummingbirds

Transcription Notes:
Moved "-mingbirds" from beginning of next page, per hyphenation rule.