Many birds appear monomorphic to humans: both sexes have the same plumage. In what way do many birds vary across the sexes in plumage color that humans cannot perceive?

Question

Quizplus · Accepted Answer

Birds often vary in ultraviolet coloration between sexes, a spectrum of light that humans cannot perceive. This means that although the birds may appear the same to us, they can look quite different to each other in the ultraviolet part of the spectrum.

Many Birds Appear Monomorphic to Humans: Both Sexes Have the Same