https://www.binghamton.edu/news/story/6207/beyond-black-rese...

> It turns out that crows lack UV-reflective patches, and that the sexes really do look the same, plumage-wise. However, the research in Yorzinski’s lab unearthed subtle changes that indicate age: On the sides, back and even under the tail, feathers changed in hue, both in the human visual range and in the UV or violet range as the birds reached the age of 3.