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Mixed Diglossini, Sept. 23, 1962, IV
33

[[left margin]] Albi  Glor [[/left margin]]
10:25. Hear the presumed Albi singing. Sings 6 or 7 songs. Then shuts up and a neighboring Glor sings (I don't know if there was a slight overlap or not.)

[[left margin]] Albi  Glor [[/left margin]]
If there is only a single Albi here, its territory must overlap several Glor territories. But I don't think I have heard any Glors singing in exactly the same places as the Albi. If there are 2 Albis here, their territories may be scattered between Glor territories.

[[left margin]] Glor [[/left margin]]
One presumed Glor (not seen well) utters song "zewa zewa zewa zeeee"✓

[[left margin]] Glor [[/left margin]]
I am rather coming to the conclusion that both Glor and intermediums must be here; but that I am failing to recognize the latter. Perhaps the blue of the latter is difficult to separate from black in the field? (Some of the birds I have seen looked rather blueish on the back, but I have presumed that this was due to light reflected from the rather glossy black of Glor.) In this connection, it may be significant that my drawings of song postures of supposed "Glor"s are quite different. The sketch on page 30 is quite Conirostrum - like in proportions.

[[left margin]] Albi  Glor Gen [[/left margin]]
The supposed Albi was nearly silent right at dawn this morning. Presumably it couldn't get a word in edgewise. I have just realized that this effect will tend to promote micro-geographical separation of species. A single bird in an area dominated by another species will hardly be able to do any "advertising" at all. Whenever a species moves into a new area, there is probably strong selection pressure against it — with a definite "threshold" is passed.

Transcription Notes:
intermedius - part of the name of some birds like warbler or masked weaver, but is she using a plural form of a species name? intermedium - a carpal in the center of the wrist joint, or a tarsal in the center of the ankle joint. Conirostrum - a small tanger