Chick begging as a signal: are nestlings honest?

Begging by dependent avian offspring is known to correlate with hunger level, and parents use this as a signal of brood demand to adjust their chick feeding behavior. While there is information on how each chick adjusts its begging to its own condition, little is known of how chicks adjust to the state of their nest mates. In two experiments we manipulated the competitive environment of individual European starling (Slumus vulgaris) chicks by altering the state of nest mates while holding the state of target chicks constant. In the first experiment we placed the target chick's nest mates in neighboring nests with brood sizes of two, five, or eight chicks. Following the manipulation we returned them to their own nests and recorded begging behavior on videotape. In the second experiment we separated a target chick from its siblings and manipulated feeding level in the laboratory. The siblings were fed at one of three levels; meanwhile, all the target chicks were fed at the intermediate level. After the manipulation we placed the target chicks with their siblings and recorded their begging in response to an artificial stimulus. In neither experiment was the begging effort of the unmanipulated target chicks affected by the changes in begging behavior of their siblings. This result supports the view that begging is a reliable signal of individual chick state and does not involve responses to the effort of nest mates.