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 the ir chick feeding behavior. While there is information on how each chic k adjusts its begging to its own condition, little is known of how chi cks adjust to the state of their nest mates. In two experiments we man ipulated the competitive environment of individual European starling ( Sturnus vulgaris) chicks by altering the state of nest mates while hol ding the state of target chicks constant. In the first experiment we p laced the target chick's nest mates in neighboring nests with brood si zes of two, five, or eight chicks. Following the manipulation we retur ned them to their own nests and recorded begging behavior on videotape . In the second experiment we separated a target chick from its siblin gs 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 targe t 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 r esponses to the effort of nest mates.