London, April 16 (IANS) Where do birds get their red feathers from? For instance, the red carotenoids that give the common crossbill its red colouration are produced in the liver, not the skin, as previously thought, according to a study.
Their findings have implications for understanding the evolution of colour signalling in bird species.

Esther Del Val from the National History Museum in Barcelona, Spain and her team show for the first time that, contrary to previous perception, the liver acts as the main site for the synthesis of carotenoids responsible for the birds’ coloration, not the skin.

Carotenoids have important physiological functions, including antioxidant properties. Carotenoid pigments are also used by many bird species as colourants, and are responsible for most of their red, orange and yellow coloration.

In particular, carotenoid-red colouration in birds has been shown to act as an ornament, signalling the nutritional and health status of the individual and its ability to locate high quality resources.

The researchers examined the carotenoid content of the liver, blood, skin and feathers of seven common crossbills (finches) in which adult males display carotenoid-based coloration on the throat, breast and rump, said a National History release.

They were particularly interested in the anatomical origin of the birds’ red plumage.

They found the primary red feather pigment of male crossbills in the birds’ liver and blood, implying that the carotenoids are synthesised in the liver and then travel to the peripheral tissues via the bloodstream.

These findings were published online in Springer’s journal Naturwissenschaften.