Hidden carotenoids in the powder down of herons

Vivid plumage colors are some of the best examples of elaborate trait evolution resulting from sexual selection. Bird feathers often contain high concentrations of pigment or intricate microstructures for reflecting light at distal feather tips, in order to maximize color presentation to intended viewers (e.g., prospective mates, rivals). However, here we describe a rare form of “hidden” plumage coloration, whereby several species of heron...