On the oxidative cost of begging: antioxidants enhance vocalizations in gull chicks

Offspring solicit food to their parents by begging displays, which are important in the parent–offspring communication. Most theoretical approximations on this behavior have centered on the view of begging as an honest signal of need or as a form of scramble competition for resources. In both signaling models, costly begging is necessary to stabilize the begging strategy at equilibrium. Nevertheless, evidence supporting begging as costly behavior remains scarce. We investigated whether oxidative stress may represent a general form of proximate cost of begging and also whether begging is related to offspring nutritional condition. To test this, we experimentally modified the chicks’ nutritional condition and vitamin E availability and measured the effects on different begging components. The intensity of all begging components increased in chicks that were intake restricted, whereas vitamin E specifically enhance the total number of chatter calls given by chicks, mainly in those with a lower body size. Our results suggest that begging behavior is an antioxidant demanding activity and support the idea that oxidative stress may be a cost of begging. Our findings also suggest that begging behavior may be an honest signal of the nutritional and oxidative status of the chicks.