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’ faces bright yellow. The more dung they eat, the brighter the yellow. “Surplus carotenoids would diffuse to the skin and the resulting yellow colouration could have become a useful signal in mating displays,” says Juan Negro’s team at the Spanish government’s DoƱana Biological Station in Seville (Nature, vol 416, p 807).
In feeding experiments on four captive birds, they proved that the birds extract a yellow carotenoid called lutein from…
