Male nightingales spend the winter practising

DESPITE THE ideas of Julia Monk and her colleagues on the frequency and normality of same-sex mating behaviour among animals (see article), some species do work hard to attract the opposite sex. That is why birdsong fills the air during the spring and summer breeding season. What has proved vexing to ornithologists is understanding why birds that migrate to warmer climes in winter often carry on singing even though there is no breeding to be done and no need to defend a territory. But a study ju...