FLASHY males have superior sperm – at least in the bird world. A study of wild great tits suggests that sexual ornamentation, in this case vibrant plumage, may reliably signal the quality of a male’s sperm.
Sperm can suffer damage by free radicals when an animal is stressed, for example when fleeing predators or even working too hard. One way of mopping up free radicals is with antioxidants. As the plumage of some birds is made from antioxidants called carotenoids, it had been proposed that the intensity of the colour could indicate the bird’s capability for dealing with free radicals, and…
