Egyptian Vultures Neophron percnopterus and Ostrich Struthio camelus eggs: the origins of stone-throwing behaviour

Experiments were carried out on wild and hand-reared Egyptian Vultures to investigate the origins of the stone-throwing this species uses to break into Ostrich eggs. There was no evidence of cultural transmission for stone-throwing through copying experienced birds. A naïve captive-reared bird threw stones once an Ostrich egg had been linked with a food reward. The origins of aimed stone-throwing are probably related to the unaimed throwing of small eggs, since the actions are similar, and all tested birds strongly preferred to throw rounded or egg-like stones, rather than jagged ones, at Ostrich eggs.