Hunger is not the only determinant of nestling begging behavior and parental feeding in the Black-Billed Magpie Pica pica

Nestlings can employ a combination of tactics to obtain provisioning from the parents. In this observational study, we examined whether nestling begging behavior reflects hunger level and how parents respond to nestling begging in the Black-billed Magpie Pica pica by putting small video-cameras in six Magpie nests. Our results revealed a strong effect of nestling begging behavior on parental feeding. Begging earlier than others and stretching the neck towards the parent was important in inducing parental provisioning regardless of age of the nestlings. Being closer to the nest entrance slightly increased the chance of being fed, but did not influence parental feeding priority. The number of nestling begging events increased with the time interval since the last feeding, which indicates that begging frequency reflects the hunger level of the brood. However, in contrast to what can be predicted when begging behavior reflects hunger levels of nestlings, nestlings increased their begging level when parents provided more feedings in the previous visits and vocalized begging negatively affected the probability and the order of being fed by the parent. In addition, sensitivity in begging behavior and parental feeding decisions depended on nestlings' age, which suggests a possibility that parental feeding decisions change with growth stages of nestlings. Our results imply that begging behavior and food allocation in Magpies does not solely determined by the hunger level of nestlings.