Do nestlings increase their begging in response to enhanced sibling competition in European Starlings, Sturnus vulgaris?

Abstract

In parent-offspring interactions, nestlings signal their hunger to parents by begging. Parents typically respond by increasing their provisioning rate. This type of communication involves specific vocalizations, postures, and gaping. Begging intensity has been found to honestly reflect hunger levels in European Starlings (Sturnus vulgaris), and not be a result of sibling rivalry (dishonest signal). I examined whether begging was an honest signal in a Nova Scotia population of European Starlings, or if it could be influenced by sibling rivalry. I analyzed nestling vocalizations occurring over a 30-min period in 21 nestboxes; each nestbox underwent both a control (natural conditions) and an experimental trial (3-min loop of nestling begging vocalizations from the preceding day was played back for an hour to simulate increased sibling competition for food). I predicted that if nestlings were affected by the enhanced begging of their siblings, they would have an increased number of begging bouts, and produce begging calls for longer during the experimental trial compared to that of the control. However, when looking at the total duration, there was no significant difference between control and experimental trials. Contrarily, there were significantly more begging bouts in the experimental, this did not influence the overall duration. European Starling nestlings did not beg more when presented with increased begging.