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Two different kinds of Three-striped Warblers (Basileuterus tristriatus) occurring in South America (left: East Andes of Colombia; right: a recently discovered population from the San Lucas mountains of Colombia). Note the differences in plumage coloration. While somewhat differing in voice, plumage and some measurements, the couple did not diverge as much as other related warblers that actually co-occur did. These are about as close as subspecies occurring on different mountain ranges could be. However, they marginally failed the proposed new benchmark for species rank.

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