Published online 25 April 2002 | Nature | doi:10.1038/news020422-14

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Faeces brings colour to birds' faces

Endangered vulture eats excrement to attract mates.

An Egyptian vulture: his yellow face gets the girls.An Egyptian vulture: his yellow face gets the girls.

Eating cow, goat and sheep excrement gives the Egyptian vulture the edge in the mating game.

Ungulate droppings contain pigments called carotenoids, which birds cannot produce for themselves. Carotenoids are nutritious, but more importantly, they keep the area around the vultures' eyes bright yellow.

A yellow face makes the fluffy white birds more attractive to mates, J. J. Negro of the Estacion Biologica de Donana in Seville, Spain, and his colleagues have found1. "The yellower the better," says Negro.

This faeces-fuelled face ornamentation may impress potential mates, as it signals that the bird is strong enough to withstand the infection risks associated with eating excrement. Like the peacock's high-maintenance tail, this could be an example of the 'handicap principle' of natural selection.

Indeed, the healthiest birds have the brightest faces, the researchers discovered. "Males and females advertise their condition to potential mates," says Negro.

Negro's team found high levels of the carotenoid lutein in both cow dung and vulture skin. To test this link further, the researchers fed four birds at Jerez Zoo in Spain exclusively on cow dung for ten days. At the end of this period, all four birds had higher lutein levels in their plasma than beforehand, when they were on a meat diet.

Ungulate faeces are loaded with parasites, but are also rich in protein from eggs and larvae that dung beetles and flies lay in it.

In Spain, France and Italy, where the endangered Egyptian vulture (Neophron percnopterus) is most common, its endearing habit has earned it the nicknames 'churretero' and 'moniguero', meaning 'dung-eater'. 

  • References

    1. Negro, J. J. et al. An unusual source of essential carotenoids. Nature 416, 807 - 808 (2002). | Article | ISI | ChemPort |