Compensation for predator-induced reduction in nestling feeding rate in the Great Spotted Woodpecker

Abstract

Parent birds make efforts to prevent the immediate costs of predation through plastic behavioural responses to the actual predation risk, but this may incur future costs for offspring due to reduced parental care. However, the temporary nature of predator encounters suggests that nestling feeding reduced during the risky periods may be later compensated for by an increased feeding effort (the predation risk allocation hypothesis). We tested this prediction in the Great Spotted Woodpecker (Dendrocopos major) confronted with its major nest predator/competitor, the European Starling (Sturnus vulgaris). A brief encounter with a live starling was followed by a reduction in the nestling feeding rate, but the lost feedings were subsequently compensated for by an increased feeding rate. This compensatory effect was higher in older nestlings that are highly demanding in terms of energy requirements and fitness value from the parents’ perspective. Thus, birds are potentially able to respond not only to the immediate risk of nest predation by nest defence but also to compensate for the potential costs of nest defence in terms of unfulfilled nestling demands. However, data on the amount of delivered food are necessary to distinguish whether parents truly compensate for lost feeding or whether the increased feeding frequency represents a nest guarding strategy.