It is one of the most striking sights of autumn. As days shorten and the weather cools, black clouds gather over Britain's skies. These dark spectacles have nothing to do with the weather, however. They are made up of thousands of starlings swirling and swooping in the air, performing aerial ballets that appear to be synchronised. Sometimes, flocks shift in shape from globes to hourglasses, thickening and thinning in the atmosphere.
The behaviour of these murmurations of starlings has puzzled scientists for years. Some researchers have argued that they are created by one or two starlings who lead the rest of the birds in these strange performances. Others have suggested more intriguing causes, such as the British ornithologist Edmund Selous who claimed the birds were responding to telepathic signals from their mates. But now a Dutch scientist, Charlotte Hemelrijk, of Groningen University, in an article in the online journal PLoS ONE, has proposed a far simpler idea: that this seemingly sophisticated behaviour can be explained using only a few simple behavioural rules. And not only are these rules true for starlings, she says, they are also true for other creatures such as fish.