Parent-absent begging and the risk of nest predation

Despite the fact that parent-absent begging (PAB) has been studied as a communication tool during competition between nestlings for food or as a signal of need, its role in nest predation has been poorly investigated. In this study we examined whether the natural level of Common Cuckoo (hereafter “Cuckoo”) PAB increases the risk of artificial nest predation (n = 48) by using three types of experimental playback of parent-present begging (PPB) which differ in the presence or absence of additional PPB, PAB or periods of silence. Contrary to our predictions, we did not find a significant difference in daily survival rates between PPB + PAB vs. PPB + PPB nests or between PPB + PAB vs. PPB + silence nests, indicating that the natural level of Cuckoo PAB did not influence nest vulnerability to predation. Moreover, we did not find a significant difference between nests with any of the types of playback and completely silent control nests, suggesting that not only PAB, but also begging behaviour itself, does not present an important predation cost for nestlings, at least not in cases when nestlings beg at the natural level used in our experiment. As we filmed all experimental nests during their exposure to predators, we were able to show that eight of 20 filmed nest-predation events were caused by predators that never or rarely predate upon passerine nests. Excluding predation events by these unlikely predators, however, did not change our original results. Nonetheless, we advocate direct identification of nest predators to strengthen the interpretation of future studies on the predation cost of begging.