How Bearded Vultures get their orange colour in the wild
Adult Bearded Vultures often have a deep orange-red tinge on their plumage, which is variable from bird to bird and region to region. It is known that the colour come from birds bathing in mud rich in iron oxide.
Scientists have noticed that the birds' age and size are directly correlated to the intensity of colour. It is theorized that the orange hue is a status symbol. More soiled feathers indicates that the Bearded Vulture had the time and resources to find an adequate place to bathe; the brightest-coloured vultures should have the most territory and knowledge of their surroundings. Until recently this ‘bathing’ has been largely unobserved in the wild so most of the information gathered has been through studying captive birds.
Stéphane Duchateau (from GOPA) and Ramuncho Tellechea (from the Office National des Forêts) put a camera trap near a ferruginous source in the French Pyrenees and have captured some video and images of the Bearded Vultures bathing.
After one year of observations, they have seen at least 7 adult Bearded Vultures regularly using the site. Each bird came to the site between 2 and 14 times each between August 2014 and December 2015, both alone or in pairs (a third of the observations). They have also observed one violent fight over the site between two adults from different pairs.
Bearded Vultures visited most often between the end of August to the end of October, and then in March when the winter is over, but Bearded Vultures can bath on the ferruginous source even when it is very cold, as they have been seen there in very cold weather.
Vulture Conservation Foundation
20 June 2016
