Appearance
There are significant differences between the populations east and west of the Andes, leading to suggestions that the two should be regarded as separate species, in which case the population west of the Andes retains the English name yellow-margined flatbill but with the scientific name ''T. flavotectus'', while the Amazonian population retains the scientific name ''T. assimilis'' but with the English name Zimmer's flatbill.Both population closely resemble the yellow-olive flatbill, and are typically best separated from that species by voice.
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