Male common crossbill (Loxia curvirostra) WILDLIFE GmbH / Alamy
In a kind of post-workout glow, male crossbills that work harder when flying will grow redder plumage. The findings reveal that the processes that generate red feather pigments in the birds may be partly driven by the revving of the metabolic engines inside cells, called mitochondria.
Many animals acquire their bright colours from compounds in their diet. Male common crossbills (Loxia curvirostra) take in yellow carotenoid pigments from their food and use enzymes to convert the pigments into vibrant, red ketocarotenoids, stored in the feathers.
Scientists have long interpreted this blush…
