Keep your feathers stunning! Preen oils enhance carotenoid-based plumage colouration

Plumage coloration plays an essential role in social communication in birds. Specifically, carotenoid-based colouration is a well known example of quality signal: high quality individuals (those in better body condition, healthier or possessing a prime immune system) signal their status by developing a vividly coloured (i.e. carotenoid-rich) plumage. However, like humans, many bird species try to enhance their natural appearance by applying “cosmetic” substances on their body.

            In a recent study (Pérez-Rodríguez et al. 2011) we have demonstrated that preen oils that birds produce in the uropygial gland (a small organ located near the base of the tail) may have other functions apart of maintaining the flexibility and waterproofing of feathers. We found that preen oils specifically enhanced those colour features of the carotenoid-pigmented tail feathers of bohemian waxwing (Bombycilla garrulus) that birds use as quality indicators. In contrast, soil accumulated in these feathers exerted the opposite effect.

These results show the importance of preening behaviour for birds. During these activities, birds remove dirt from feathers and extend adequate amounts of preen oils around their bodies. Apart of keeping their feather ready for flight, this seems to help them to keep a stunning appearance!