With stunning bravado, Egyptian vultures eat animal faeces to attract mates. Dung from sheep, cows and goats is rich in carotenoids, which turn the skin on the vultures鈥� faces bright yellow. The more dung they eat, the brighter the yellow. 鈥淪urplus carotenoids would diffuse to the skin and the resulting yellow colouration could have become a useful signal in mating displays,鈥� says Juan Negro鈥檚 team at the Spanish government鈥檚 Do帽ana Biological Station in Seville ().
In feeding experiments on four captive birds, they proved that the birds extract a yellow carotenoid called lutein from dung. Negro points out that the depth of yellowness might also reflect the strong immune systems of birds who take big risks eating such parasite-laden food, and so might help them establish dominance.
