In preparing for a lecture this week on avian coloration, I had organized my notes around the three main classes of pigments in feathers and the structural colors that result from light scattered from structures on those feathers. At the most basic level (and the only one for which I can claim any understanding), melanins produce most of the blacks, browns, and grays, while carotenoids are the source of the yellows, oranges, and reds. Any blue or green we see on birds results from light refracted as it passes through those feathers, with blue resulting from generally gray or black feathers that reflect “blue” wavelengths, and green produced by yellowish feathers that reflect those wavelengths. Thus, the Eastern Bluebird isn’t really a blue bird.
There is a third class of pigmentation in birds that can result in a wide range of colors, from sombre browns to brilliant blues and reds. These pigments are the porphyrins, and they’re super-cool first because as agents of avian coloration, they occur only in the bustards, turacos, and owls.
They’re also cool because they glow red under UV light. Wait . . . what?!
Okay, so I had to try this (and don my white lab coat for dramatic effect). The result? It worked!
I thought it might be most noticeable on the more intense colors of our model (a road-killed Great Horned Owl) but the opposite was true: It was the pale creamy-buff feathers on the flank that provided any fluorescence at all. Anyway, this was fascinating and it was fun to show the students how I’m still learning too.