Use of Stones by the Black-Breasted Buzzard Hamirostra melanosternon to Gain Access to Egg Contents for Food

Abstract

A captive Black-breasted Buzzard Hamirostra melanostemon cracked Domestic Chicken Gallus gallus eggs by using its bill to throw 15-65 g rounded stones at them in order to feed on the contents. The throwing method, feeding and post-feeding behaviour are described. Throwing accuracy improved during a series of trials conducted over 26 days. The egg-breaking activity is discussed in terms of tool usage and in terms of learned versus non-learned behaviour.