The main reason that birds flock together is to avoid being eaten, a study of island birds has confirmed.
Guy Beauchamp at the University of Montreal, Canada, looked at the flocking behaviour of 46 species living in 22 island habitats around the world where there are few, or no, predators.
He found that the islanders were less likely to travel in flocks than their mainland counterparts, and that when they did the flocks tended to be smaller. Low predation affected whether and how they fraternised, but variables such as body mass, food type and the openness of the habitat did not. Ten of the species studied, including the Laysan duck of the Hawaiian archipelago (above) and the St Helena plover of the South Atlantic, have ceased to flock at all (
But many birds still travel in groups even when there are few ...
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