This is the Egyptian vulture. Scientists believe that its beautiful orange beak and yellow face helps it to attract mates.
But it has a problem: that coloring is produced by beta-carotene, and the bird needs a ton of beta-carotene to produce good coloration.
The best place to find beta-carotene, it turns out, is in the feces of hooved animals. And so the bird scarfs down that dung.
The full story:
http://news.bbc.co.uk/hi/english/sci...00/1946291.stm