Rates of oxygen consumption during begging behaviour in nestlings of seven species and distress call behaviour in adults of eight species of Australian birds were measured. A transparent mask coupled to an open-flow respirometry system was used, and calling was elicited by the presentation of food or by the perceived threat of a predator. Distress calling significantly increased oxygen consumption above the measured resting levels in six of the species of birds tested. The factorial increase in oxygen consumption during distress calling was independent of body mass. In most cases, begging behaviour in juvenile birds caused a significant increase in metabolic rate, with some individuals showing factorial increases over fourfold. There was a significant negative correlation between body mass and the factorial cost of begging behaviour.