In some finch species, BCO2, a gene that encodes a carotenoid-destroying enzyme, is expressed in many female finch feathers but not in many male feathers. This generates dramatic sexual dichromatism that makes males dazzle while females look relatively drab. In common canaries, which are not sexually dichromatic, both males and females have little BCO2 expression in their feathers.
Published in The Scientist magazine, September 2020. Writing by Rachael Moeller Gorman.