A much-loved garden bird has been exposed as a ruthless killer after being observed seeking out and eating hibernating bats. The great tits were provoked into the unusual behaviour after suffering food shortages during particularly harsh winter weather. Over the course of two winters, ornithologists observed the birds searching for, killing and eating 18 bats in caves in the Bükk Mountains in northeast Hungary. The birds normally live on seeds and insects such as caterpillars and spiders but during the winter these can be in very scarce supply. In particular, snow cover can make it impossible for the great tits...