What feature inspired the species epithet verticalis for Tyrannus verticalis?

Answer

Pale or whitish edging on the inner webs of the tail feathers visible in flight

The species epithet *verticalis*, meaning 'vertical' in Latin, is specifically linked to a distinctive visual marker observed when the Western Kingbird is flying. When the bird fans its tail, the pale or nearly white edging present on the inner webs of the tail feathers creates a striking, conspicuous vertical pattern against the darker sections of the tail. This feature serves as a key visual identifier.

What feature inspired the species epithet verticalis for Tyrannus verticalis?
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