We now know that 90 per cent of all female birds routinely copulate with multiple males and, as a result, a single clutch of eggs can have many fathers. It turns out that the flashier the male, the more likely the female is to be unfaithful. Birkhead recently discovered that species displaying the greatest sexual dimorphism hide the greatest infidelity, the most extreme known case being Australia’s superb fairy wren. As the name suggests, males boast some rather splendid blue seasonal plumage and will even woo the female, a classic little brown job, with carefully plucked yellow flowers. The
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